Past Events

The nondestructive detection of optical photons is an enabling technology with applications in quantum information, simulation and communication. We present a detection scheme that continuously detects photons without destroying them. Photons to be measured are sent through an ensemble of Cesium atoms, where they travel as slow-light polaritons that are, in turn, coupled to a high finesse optical cavity. The atomic component of the polariton rotates the polarization of light that is transmitted through the cavity, which we detect. We show that the system is capable of non-destructively detecting individual signal photons by measuring a second-order correlation function between the signal and detection paths of g_2(0)>5.

Light carries momentum and can exert substantial forces on micro- and macroscopic objects ranging from single atoms to kg-scale mirrors. In high vacuum, optically levitated dielectric microspheres achieve excellent decoupling from their environment and experience minimal friction. Hence they can be used for sensitive force measurements. We have shown that such beads can be stably trapped under high vacuum conditions for long time periods and can be used for attonewton force measurements in a dual beam optical trap. I will describe our progress towards using these sensors for tests of the Newtonian gravitational inverse square law at micron length scales. Optically levitated dielectric objects also show promise for a variety of other applications, including searches for gravitational waves and experiments involving quantum optomechanics.

[1] G. Ranjit, D. Atherton, J. Stutz, M. Cunningham, and A.A. Geraci, Phys. Rev. A 91, 051805(R) (2015).

[2] A. Arvanitaki and A. A. Geraci, Phys. Rev. Lett. 110, 071105 (2013).

[3] A.A.Geraci, S.B.Papp, and J.Kitching, Phys. Rev. Lett. 105, 101101 (2010).

Quantum matter coupled to enhanced optical fields in confined geometries such as resonators and waveguides offer a promising platform to study emergent phenomena far-from-equilibrium [1]. In my talk I will discuss our recent efforts [2,3,4] at understanding what a quantum phase transition of photons may look like in a lattice of Cavity Quantum Electrodynamics systems, where photons become itinerant. Surprisingly this has lead us back to the very origin of Quantum Electrodynamics and the Quantum Theory, namely to Planck and Einstein's theory of thermal cavity radiation. We find a modification to the Planck-Einstein theory due to the backaction from (material) oscillators and show that a Cavity QED network displays an instability towards a ferroelectric phase when light-matter coupling is sufficiently increased. The true potential of coupled light-matter systems is however unleashed in driven Cavity QED networks [4]. I will discuss a general method to use photon-mediated interactions between qubits to drive them to a long-distance entangled state with an arbitrarily long lifetime [5]. We find that photon-mediated interactions provide a highly versatile toolbox to engineer the unitary and dissipative dynamics of spatially separated qubits, with important implications for dissipative stabilization of pure many-body states of qubits [6].

[1] A. Houck, H. E. Tureci, J. Koch, Nature Physics 8, 292 (2012).
[2] M. Schiro, M. Bordyuh, B. Oztop, H. E. Tureci, Phys. Rev. Lett. 109, 053601 (2012).
[3] M. Schiro, M. Bordyuh, B. Oztop, H. E. Tureci, J. Phys. B 46, 224021 (2013).
[4] M. Schiro et al, arxiv:1503.04456
[5] C. Aron, M. Kulkarni, H. E. Tureci, Phys. Rev. A 90, 062305 (2014).
[6] C. Aron, M. Kulkarni, H. E. Tureci, arxiv:1412.8477

Having the shortest optical1,2,3 and soft x-ray fields4 as a part of its repertoire, attosecond physics has recently opened up new avenues for exploring ultrafast electronic processes in atoms5,6, molecules7, surfaces8 and nanostructures9. I will discuss how modern advancements of the “ultrafast toolbox” allow for the first time, the exploration and control of fundamental electronic phenomena in condensed media. Electron motion in bulk media, driven by intense, precisely-sculpted, optical fields give rise to controllable electric currents, the frequency of which extends to the multi-Petahertz range9-10, advancing lightwave electronics10 to new realms of speed and precision. Coherent extreme ultraviolet radiation emerging by these coherent charge oscillations9 offers direct insight into structural and dynamical properties of the underlying medium which were previously inaccessible to conventional solid-state spectroscopies. By endowing essential x-ray spectroscopies of solids with attosecond temporal resolution, optical half-cycle fields, combined with extreme ultraviolet pulses, offer for the first time, access into the attosecond dephasing of electronic excitation of highly-correlated condensed phase electronic systems11. We anticipate these new capabilities to result in far reaching implications to fundamental and applied, electronic and photonic sciences.
[1] Goulielmakis E. et al., Science 305, 1267 (2004) [2] Wirth A. et al., Science 334, 195 (2011). [3] Hassan M. Th et al., Nature submitted ( 2015) [4] Goulielmakis E.et al., Science 320, 1614 (2008).[5] Goulielmakis E. et al., Nature 466, 739 (2010). [6] Kienberger R. et al., Nature 427, 817 (2004) [6], Smirnova et. al, Nature 460,972(2009) [7] Cavalieri A L et al., Nature 449,1029 (2007) [8] Krueger M et al. Nature 475,78 (2011) [9] Luu T.T. et al., Nature 521,498 (2015), Garg el., Submitted (2015), [10] Goulielmakis E. et al., Science 317, 769 (2007). [11] Moulet A. et al., in preparation (2015)

Significant efforts have been made to interface cold atoms with micro- and nano-photonic systems in recent years. Originally, it was envisioned that the migration to these systems from free-space atomic ensemble or macroscopic cavity QED experiments could dramatically improve figures of merit and facilitate scalability in applications such as quantum information processing. However, there is a growing body of work pointing to an even more intriguing possibility, that nanophotonic systems can yield fundamentally new paradigms to manipulate quantum light-matter interactions, which do not have an obvious counterpart in macroscopic setups. Here, we describe an example of such a new possibility, involving the coupling of atoms to photonic crystals. In particular, we show that when atoms have transition frequencies aligned within photonic crystal bandgaps, the atoms can become dressed by localized photonic "clouds" of tunable size. This cloud behaves much like an external cavity, but one which follows the position of the atom. This phenomenon allows one to mediate and control long-range interactions between atomic internal degrees of freedom (spin), atomic motion (phonons), and photons. The multi-physics coupling can be utilized to design quantum systems with a rich variety of functionalities. We will discuss several examples, including strongly correlated many-body states of atomic spin and motion, and the "binding" of photons into extended molecules.

BIOGRAPHY
Darrick Chang has been a professor at the Institute of Photonic Sciences (ICFO) in Barcelona since 2011, and leads the research group for Theoretical Quantum Nanophotonics. Previously, he received his B.S. and PhD degrees in physics from Stanford and Harvard, respectively, and was a postdoctoral fellow at the Institute for Quantum Information at Caltech. His group is broadly interested in the use of nanophotonic and nanomechanical systems as platforms for novel quantum devices and to explore new quantum phenomena. Specific research interests in recent years include the optical properties of graphene, interfaces between cold atoms and nanophotonic systems, optical trapping techniques, and quantum vacuum forces. He is the recipient of an ERC Starting Grant.

Our lab has been asking the question: is it possible to exploit atom-atom correlations and entanglement to advance the field of precision measurement? We have explored this question along two fronts that surpass quantum and thermal limits on precision measurements: spin-squeezed states that surpass the standard quantum limit on phase estimation by as much as 17.6(4) dB, and superradiant lasers that could be 10,000 times less sensitive to thermal and technical vibrations of the optical cavity’s mirrors. These techniques may one day impact a broad range of quantum sensors and physical measurements including atomic clocks, matter-wave interferometers, and lasers with sub-millihertz linewidth or equivalent coherence lengths extending from the earth to the sun.

Phenomena associated with the topological properties of physical systems can be naturally robust against perturbations. The best known examples are quantum Hall effects in electronic system, where insensitivity to localproperties manifests itself as conductance through edge states that is insensitive to defects and disorder. In this talk, I demonstrate how similar physics can be observed for photons; specifically, how various quantum Hall Hamiltonians can be simulated in an optical platform. I report on the first observation of topological photonic edge states using silicon-on-insulator technology, and the measurement of the corresponding topological invariants. Furthermore, the addition of optical nonlinearity to this system provides a platform to implement fractional quantum Hall states of photons and anyonic states that have not yet been observed in any physical system. More generally, the application of these ideas could lead to the development of optical devices with built-in protection for classical and quantum information processing.



Biography

Mohammad Hafezi is an Assistant Professor of Electrical and Computer Engineering at the University of Maryland (UMD), and a fellow at the Joint Quantum Institute (NIST-UMD) and IREAP. After obtaining his Ph.D. from the Physics Department at Harvard University, he moved to the Joint Quantum Institute as a postdoc in 2009. His research is at the interface of theoretical and experimental quantum optics and condensed-matter physics with a focus on fundamental physics and applications in quantum information science, precision measurement, and integrated photonics. His recent awards include a Sloan Research Fellowship and a Young Investor award of the Office of Naval Research.

Stanford Research Highlights:

Supermode-polariton condensation in a multimode cavity QED-BEC system (Alicia Kollar)

Investigations of many-body physics in an AMO context often employ a static optical lattice to create a periodic potential. Such systems, while capable of exploring, e.g., the Hubbard model, lack the fully emergent crystalline order found in solid state systems whose stiffness is not imposed externally, but arises dynamically. Our multimode cavity QED experiment is introducing a new method of generating fully emergent and compliant optical lattices to the ultracold atom toolbox and provides new avenues to explore quantum liquid crystalline order. Looking forward, spin glasses may arise due to the oscillatory, frustrated, and tunable-range interactions mediated by the photons in the multimode optical cavity. It will thus be possible to use spinful atoms in cavities to realize models of frustrated and/or disordered spin systems, including neuromorphic computation in the context of the Hopfield associative memory. We will present our first experimental result, the observation of a supermode-polariton condensate via a supermode superradiant phase transition.


Probing Ultrafast Electron Dynamics in Atoms and Molecules (Lucas Zipp)

As our ability to probe atomic and molecular processes in the time domain approaches the attosecond time scale, it has become possible (and necessary) to revisit some fundamental ideas on how processes like photoionization occur in the time domain. Several recent experiments have investigated measuring attosecond-scale “Wigner” delays in single photon ionization [1,2]. I will present our results extending these measurements to the strong field regime, allowing us to probe the intrinsic time delay experienced by an electron as it is ionized in a strong, nonperturbative laser field [3]. In the second part of the talk I will discuss a recent experiment tracking the angular motion of an electron wave packet in a Rydberg manifold of molecular nitrogen. We are able to see directly in the time domain a process of “l-uncoupling” that up until now has only been inferred from spectroscopic data [4].

[1] K. Klünder et al, "Probing Single-Photon Ionization on the Attosecond Time Scale," Phys. Rev. Lett. 106, 143002 (2011).

[2] M. Schultze et. al, "Delay in Photoemission," Science 328, 1658–1662 (2010).

[3] L. J. Zipp, A. Natan, and P. H. Bucksbaum, "Probing electron delays in above-threshold ionization," Optica 1, 361–364 (2014).

[4] R.-Y. Chang et al, "Observation of L uncoupling in the 5Δg1 Rydberg state of Na2," The Journal of Chemical Physics 123, 224303 (2005).

In recent years, systems of ultracold atoms in optical lattices have opened new opportunities for exploring time-dependent many-body dynamics. In addition to coherent phenomena, it has become possible to engineer open quantum systems, drawing new connections between many-body physics and concepts from quantum optics. Dissipation arises naturally in the form of light scattering and particle losses in these systems, and can also be directly engineered, e.g., by adding additional species to the experiment which act as a reservoir. This opens opportunities for exploring novel phenomena, and also finding new ways of preparing important many-particle states. I will discuss some of our recent theoretical work in this direction, including how effective three-body interactions between atoms in optical lattices can be controlled by photon-assisted tunnelling or enhanced via dissipative processes. I will also discuss how engineered dissipation or particle losses can be combined with properties of fermionic statistics to drive a system into entangled spin states, which have potential applications in quantum metrology.

New experimental techniques in condensed matter physics go beyond the paradigm of linear response measurements. I will use examples of resonant Xray scattering in high Tc cuprates and photo-induced superconductivity to demonstrate how new insights into experimental results can be gained by considering their nonequilibrium aspects. I will also discuss on-going experiments with ultracold atoms that can help address open problems of quantum dynamics of many-body fermionic systems.

Ultracold polar molecules featuring long-range and anisotropic dipolar interactions are emerging as a unique platform for the quantum simulation of a variety of rich and important phenomena ranging from quantum magnetism, to many-body localization, to synthetic spin-orbit coupling. However to take fully advantage of those capabilities and investigate the plethora of exotic quantum phases hosted by them it is fundamental to reach low entropy conditions.

In this talk I will describe how the combined effects of interactions, temperature, and adiabatic loading in an optical lattice act as an obstacle to the experimental realization of a low-entropy gas of polar molecules through magnetoassociation of initially prepared quantum degenerate atomic gases. Careful considerations of these effects has been key for increasing the filling fraction in recent polar molecule experiments.

Moreover, I will describe a recent experiment conducted at JILA where a lattice gas of polar molecules has been used to create a clean and tunable distribution where sites are either empty or occupied by a doublon made of one boson and one fermion. I will discuss theoretical models based on analytical methods and numerical simulations, that capture the observed far from equilibrium, many-body dynamics of the bose-fermi mixture.

Biography

I am a research fellow at JILA, NIST and CU Boulder in the group of Ana Maria Rey. I work closely with the polar molecules experiment at JILA and the trapped-ion experiments at NIST. I develop analytic methods and numerical tools to analyze equilibrium and out-of-equilibrium properties of many-body quantum systems.

In the quantum world, an object can simultaneously exist in multiple states – the “dead” and “alive” realizations of Schrödinger’s proverbial feline being a quintessential example. It is the act of measurement which drives such an exotic superposition to a more familiar classical outcome, “dead” or “alive” for the cat, thus bridging the gap between quantum mechanics and our concept of reality. However, the precise nature of this so-called wavefunction collapse remains a topic of debate at the intersection of physics, mathematics, and philosophy. Applying continuous weak measurement techniques in conjunction with Bayesian statistics to superconducting quantum circuits, we reconstruct the real-time collapse of the wavefunction describing a two-state system at the level of the individual constituent quantum trajectories that form an ensemble measurement. With this dense dataset, a variety of statistical metrics can be extracted, including the most probable path—analogous to the geodesic in space-time—between two points in Hilbert space.

Bio: A professor of physics at the University of California, Berkeley, my work is primarily experimental and focuses on the development of superconducting quantum electronics, with an emphasis on quantum information processing and quantum control. In particular, we seek to answer fundamental questions in quantum theory as well as to engineer devices that harness quantum coherence. Recent explorations include quant

In recent decades, there has been intense interest in understanding the role of geometry in band structures. In contrast to solid state systems, where geometric effects are usually observed through the response of other quantities, ultracold atoms in optical lattices offer the unique possibility of directly probing the geometry of the band eigenstates. Using a BEC in a graphene-type hexagonal lattice, we directly probe band geometry by combining Ramsey interferometry with a gradient. First, using a weak gradient, we realize an atomic interferometer in reciprocal space to detect the singular π Berry flux localized at each Dirac point, in analogy to an Aharonov-Bohm interferometer that measures the magnetic flux through an area in real-space . Next, using a strong gradient, we realize dynamics that are described by Wilson lines, which are generalizations of Berry phases to multiple, degenerate bands. We demonstrate that probing the evolution in band populations enables a tomographic reconstruction of the cell-periodic Bloch functions at any quasimomentum.

Biography

Tracy is currently a PhD student in the group of Immanuel Bloch in Munich. Previously, she received her B.Sc in physics at MIT.

Two component ultra-cold bosonic gases in optical lattices are an excellent
quantum simulator. We will present two examples in this talk.
The first part focuses on the near perfect implementation of Heisenberg chains
which is achieved using a single component Mott insulating state. Single site
addressing techniques are applied to manipulate the local spin population.
Quantum as well as thermal fluctuations cause a residual hole probability in the
initial state and the impact on coherent spin transport is an open question. We
experimentally show that coherent spin transport under these conditions is
indeed possible. Propagation of a single spin impurity results in entanglement
spreading along the spin chain which we directly detect by measuring the
concurrence between pairs of lattice sites.
The second part of the talk will be about many-body localization (MBL). Under
which conditions well isolated quantum systems do thermalize is a fundamental
question. MBL marks a general class of systems which do not thermalize.
Microscopic detection of diverging observables near the phase transition remains
experimentally challenging, and demonstration of the MBL in higher dimensions
is still demanding. We report on recent experiments on MBL of Bosons in a two
dimensional square lattice. We prepare a structured highly excited Mott insulating
state which relaxes to a thermal state for vanishing disorder. A projected on-site
random disorder potential changes the time evolution significantly and leads to
non ergodic behavior. Employing single site and single atom sensitivity we use
local observables to quantify the dynamics of the bosonic many body state for
different disorder strength. We observed the phase transition to MBL to occur
only above a critical disorder strength for interacting Bosons.

Biography

Sebastian received his Bachelor degree in 2009 at the Rheinischen Friedrich Wilhelms-Universitat Bonn, Germany with a Bachelor project on "Laser Frequency Stabilization using heterodyne interferometry for the LISA Space-craft Mission“ at the University of Florida. Afterwards He worked on "Resolved Raman sideband cooling in a doughnut-shaped optical trap“ in the group of Prof. Dieter Meschede and obtained his Master degree in 2011 from the Rheinischen Friedrich Wilhelms-Universitat Bonn, Germany. Since 2012 he is a doctoral candidate at the Max--Planck-Institut für Quantenoptik in Garching, Germany within the group of Prof. Immanuel Bloch. He is working at the single atom experiment on simulation of spin models and many-body dynamics.

The parts of a composite system can share correlations that are stronger than any classical theory allows. These so-called Bell correlations can be confirmed by violating a Bell inequality and represent the most profound departure of quantum from classical physics. We report experiments where we detect Bell correlations between the spins of 480 atoms in a Bose-Einstein condensate [1]. We derive a Bell correlation witness from a recent many-particle Bell inequality [2] involving one- and two-body correlation functions only. Our measurement on a spin-squeezed state [3] exceeds the threshold for Bell correlations by 3.8 standard deviations. Concluding the presence of Bell correlations is unprecedented for an ensemble containing more than a few particles. Our work shows that the strongest possible non-classical correlations are experimentally accessible in many-body systems, and that they can be revealed by collective measurements. This opens new perspectives for using many-body systems in quantum information tasks.

[1] R. Schmied, J.-D. Bancal, B. Allard, M. Fadel, V. Scarani, P. Treutlein, N. Sangouard, to be published (2016).
[2] J. Tura, R. Augusiak, A.B. Sainz, T. Vértesi, M. Lewenstein, A. Acín, Science 344, 1256 (2014).
[3] M.F. Riedel, P. Böhi, Y. Li, T.W. Hänsch, A. Sinatra, P. Treutlein, Nature 464, 1170 (2010).

Short Biography

Philipp Treutlein, born in Reutlingen in 1976, studied physics at the Universities of Konstanz and Stanford in 1996-2002. At Stanford, he worked in the laboratory of Steven Chu on laser cooling and atom interferometry. Back in Konstanz, he joined Markus Oberthaler's group for his diploma thesis, investigating Bose-Einstein condensates in optical lattices. From 2002-2010, Philipp worked in the laboratory of Theodor W. Hänsch at LMU Munich and the Max-Planck-Institute of Quantum Optics, first as a doctoral student in Jakob Reichel's team and later as leader of his own group. During this time, he performed experiments with ultracold atoms in chip-based microtraps ("atom chips"). He demonstrated a chip-based atomic clock and an atom interferometer, carried out first experiments on quantum metrology with entangled atoms, and explored interfaces of atoms and mechanical oscillators. In 2010, Philipp was appointed as a tenure-track assistant professor at the University of Basel, where he set up a group working on ultracold atoms, optomechanics, and hybrid quantum systems. In February 2015 he was promoted to associate professor.

The generation of quantum states carrying entanglement among propagating light fields and stationary matter is a prerequisite for fundamental test of quantum mechanics, such as loophole free Bell tests, as well as for applications in quantum communication over long distances. Current experiments achieve a remarkably high efficiency in generating and controlling such entangled states of matter, such as single atoms, atomic ensembles, and even with micro-mechanical oscillators, with pulsed light. In my talk I will present our recent theoretical studies towards extending this to continuous-wave light which may provide new perspectives for experiments operating in the regime of strong cooperativity of light-matter interactions. In particular, I will show that this approach can be used to generate deterministically long-distance entanglement of material degrees of freedom, emulate many-body quantum dynamics, and perform analog variational calculations for models of quantum field theories.

Klemens Hammerer
Institute for Theoeretical Physics and Institute for Gravitational Physics (Albert-Einstein-Institute) Leibniz University of Hannover

Recent years have witnessed substantial progress in using interactions between Rydberg excited atoms for quantum gates and entanglement generation. Nevertheless there remain several outstanding challenges that must be overcome to achieve scalable quantum computation. These include gate fidelity, atom loss, and quantum nondemolition state measurements without crosstalk to nearby qubits. After reviewing the current state of the art we will present some new ideas for simple solutions using complex atoms.

We use nano-lithography techniques to create lattice potentials in permanent magnetic films on atom chips. These lattices can be created over a large range of length scales and are used to trap mesoscopic clouds of ultracold atoms. In our current experiments we use a 10 micron lattice spacing to study Rydberg physics with clouds up to 400 atoms. In parallel, we are downscaling the lattice spacing for a new series of experiments. On these new atom chips we created lattices with lattice spacing varying from 250nm up to 5um on the same chip. I will discuss both the current experiments and the fabrication of these new magnetic potentials. These chips were patterned by e-beam lithography and etched with an Ar plasma to obtain structures with a 20nm resolution. This technique can extend the range of length scales of optical lattices to smaller scale's and therefore higher interaction energies, also it c an be used to study degenerate gases in completely engineered potential environments. In my talk I will focus on the fabrication of the magnetic chips, the construction of our new quantum gas experiment and I will show various new lattice geometries that we developed and simulated.

Dark energy could be a dynamic field - quintessence. The original and simplest model is based on so-called tracker potentials. Confirming this model would identify the dominant constituent of the universe and help understanding its history. In principle, this is possible by studying the history of the dark energy density, e.g., by improved supernova surveys, microwave-background-radiation or structure-formation studies.

Assuming a coupling between dark energy and normal matter, of roughly gravitational strength, allows us to detect search for quintessence by measuring its interaction with cold atoms in atom interferometers. We have already constrained the model more than 1000 times more strongly than the best previous experiment. Searching its entire parameter space is feasible and would either detect quintessence or rule out the model, thus characterizing the properties of dark energy.

We will discuss recent developments at a new scientific interface between quantum optics, nanoscience and quantum information science. Specific examples include the use of quantum optical techniques for manipulation of individual atom-like impurities at a nanoscale and for realization of hybrid systems combining them with nanophotonic devices. We will discuss how these techniques are used for exploring quantum nonlinear optics and quantum networks, probing non-equilibrium quantum dynamics, and developing new applications such as magnetic resonance imaging with single atom resolution, and nanoscale sensing in biology and material science.

Dramatic progress has been made in the last decade and a half towards realizing solid-state systems for quantum information processing with superconducting quantum circuits. Artificial atoms (or qubits) based on Josephson junctions have improved their coherence times more than a million-fold, have been entangled, and used to perform simple quantum algorithms. The next challenge for the field is demonstrating quantum error correction that actually improves the lifetimes, a necessary step for building more complex systems. Here we demonstrate a fully operational quantum error correction system, based on a logical encoding comprised of superpositions of cat states in a superconducting cavity. This system uses real-time classical feedback to encode, track the naturally occurring errors, decode, and correct, all without the need for post-selection. Using this approach we reach, for the first time, the break-even point for QEC and preserve quantum information through active means. Moreover, the performance of the system matches with predictions, and can be dramatically improved by making the protocol more fault tolerant. Mastering the practice of error correction, and understanding the overhead and complexity required, are the main scientific challenges remaining for reaching scalable quantum computation with this technology.

Spin-squeezed states have now been created in a range of atomic systems using a variety of methods. This talk looks at some promising alternative schemes for creating spin squeezing in cavity QED systems using cavity-mediated Raman transitions to engineer effective atom-photon and atom-atom interactions. These schemes follow on from the proposal of Dimer et al. [1] for the creation of a generalised, effective Dicke model of an ensemble of spin-1/2 atoms coupled to a cavity mode, including both linear and nonlinear (dispersive) atom-cavity couplings on a potentially equal footing [2]. We first examine this model in a regime where the dispersive coupling is very large and find that the steady state of the system can in fact be a strongly spin-squeezed Dicke state of the atomic ensemble. These states can offer Heisenberg-limited metrological properties and feature genuine multipartite entanglement amongst the entire atomic ensemble. We also consider a more general set of schemes, which utilise additional atomic internal (electronic) states or additional cavity modes to engineer alternative collective-spin models [3]. These models in turn lead to alternative methods for producing spin squeezed states not only of spin-1/2 systems, but also of integer-spin systems.

[1] F. Dimer, B. Estienne, A.S. Parkins and H.J. Carmichael, Proposed realization of the Dicke-model quantum phase transition in an optical cavity QED system, Phys. Rev. A. 75, 013804 (2007).

[2] A.L. Grimsmo and A.S. Parkins, Dissipative Dicke model with nonlinear atom-photon interaction, J. Phys. B: At. Mol. Opt. Phys. 46, 224012 (2013).

[3] S. Morrison and A.S. Parkins, Collective spin systems in dispersive optical cavity QED: quantum phase transitions and entanglement, Phys. Rev. A. 77, 043810 (2008).

Spanning condensed matter, cosmology, and quantum gases, evolution of many-body systems is hy-pothesized to be universal near a continuous phase transition. A long-sought signature of the universal dynamics is the scaling symmetry of emerging topological defects; examples include cosmic domains in early universe (T. Kibble, 1976), and vortices in quenched superfluid helium (W. Zurek, 1985).

We test the scaling symmetry and universality of quantum critical dynamics based on Bose-Einstein condensates of cesium atoms ramping across an effective ferromagnetic quantum phase transition. We observe a sudden growth of quantum fluctuations and domains separated by topological defects (domain walls). Intriguingly, the domains are anti-ferromagnetically ordered with record thermal energy scales as low as kB x 20pK. Time and length scales measured over a wide range of parameters yield precise temporal and spatial critical exponents of 0.50(2) and 0.26(2), respectively, consistent with theory. In the scaled space-time coordinate, correlations collapse to a single curve, in support of the universality hypothesis.

Understanding how an isolated many-body state thermalizes and develops entropy is foundational to quantum statistical mechanics, yet appears antithetical to basic notions that we have about entropy. An evolving quantum state can develop observables that agree with thermal ensembles, yet the unitarity of quantum evolution preserves the purity of this full quantum state in time. Hence, a pure, and in this sense, zero entropy quantum state can dynamically become seemingly entropic and thermal. In this talk, I will describe our experimental studies of thermalization in a verifiably pure many-body state, and how the entropy induced by entanglement facilitates thermalization. I will describe our experimental method for measuring quantum purity, and thereby entanglement entropy, through the interference of two copies of a many-body state. By comparing the entanglement entropy we measure to the thermal entropy expected from an ensemble, I will illustrate how thermalization is manifest locally within a globally pure quantum state, and how these observations are related to the Eigenstate Thermalization Hypothesis.

A Many-Body Localized (MBL) system describes a generic phase of matter which, even with an infinite number of degrees of freedom, fails to thermalize. Surprisingly, this breakdown of thermalization can occur even in highly exited states. As such, this phase cannot be described by conventional quantum-statistical physics which assumes an underlying temperature of the many-body system. In this talk, I will describe how can one can use a highly controllable system of ultracold atoms in optical lattices to understand and probe such a quantum many-body system.

Disorder turns out to be the key ingredient in realizing the insulating MBL state. One important challenge here is to understand the transition from a delocalized phase to the MBL phase as the disorder strength is increased. As the notion of temperature itself gets blurred, I will describe a novel method to probe ergodicity breaking based on the relaxation of local observables. I would put special emphasis on the relaxation at the MBL critical point where we observe critically slowed dynamics and will comment of the notions of Griffiths phases. If time permits, I will also show some recent results on the observation of a Floquet-MBL phase and on the possibility of MBL in two dimensions using quasi-crystals.

Time-resolved femtosecond x-ray diffraction patterns from laser-excited molecular iodine are used to create a movie of intramolecular motion with a temporal and spatial resolution of 30 fs and 0.3 Angstrom. This high fidelity is due to interference between the moving excitation and the unperturbed initial charge distribution. The initial state is used as the local oscillator for heterodyne amplification of the excited charge distribution to retrieve real-space de-novo movies of atomic motion on Angstrom and femtosecond scales. This x-ray interference has not been employed to image atomic motion in molecules before. Coherent vibrational motion and dispersion, dissociation, and rotational dephasing are all clearly visible in the data, thereby demonstrating the stunning sensitivity of heterodyne methods.

Cosmological observations indicate that dark matter (DM) constitutes 85% of all matter in the Universe, yet conclusive evidence for DM in terrestrial experiments remains elusive. One of the possibilities is that DM can be composed from ultralight quantum fields whose self-interactions lead to the formation of DM objects in the form of stable topological defects. Such DM ``clumps'', depending on the masses of underlying fields, can be spatially large on the laboratory scale. As the Earth moves through the halo of DM objects, interactions with such DM clumps could lead to measurable variations in GPS signals which propagate through the satellite constellation at galactic velocities of ~ 300 km/s. Here we use the network of atomic clocks onboard GPS satellites as a ~50,000 km aperture DM detector.
By mining over a decade of archival GPS data, we find no evidence for topological defects in the form of domain walls at our current sensitivity, which enables us to improve the present limits on certain DM--ordinary matter coupling strengths by up to six orders of magnitude.

Cavity-polaritons have emerged as an exciting platform for studying interacting bosons in a
driven-dissipative setting. Typically, the experimental realization of exciton-polaritons is based
on undoped GaAs quantum wells (QW) embedded in between two monolithic distributed Bragg
reflector (DBR) layers. Introduction of a degenerate electron gas either to the QW hosting
the excitons or a neighboring layer substantially enriches the physics due to polariton-electron
coupling. It has been proposed that such an interacting Bose-Fermi mixture can be used to
study polariton-mediated superconductivity in a two dimensional electron gas.
Transition metal dichalcogenide (TMD) monolayers, such as molybdenum diselenide (MoSe2),
represent a new class of valley semiconductors exhibiting novel features such as strong Coulomb interactions, finite exciton Berry curvature with novel optical signatures and locking of spin and valley degrees of freedom due to large spin-orbit coupling. In contrast to quantum wells or two-dimensional electron systems in III-V semiconductors, TMD monolayers exhibit an ultra-large exciton binding energy of order 500 meV and strong trion peaks in photoluminescence that are red-shifted from the exciton line by 30 meV. In this talk, he will present cavity spectroscopy of gate-tunable monolayer MoSe2 and show that in the limit of perturbative cavity coupling elementary optical excitations in this system are attractive and repulsive exciton-polarons - excitons dressed by Fermi sea electron-hole pairs. By reducing the cavity length, they reach the strong-coupling limit of cavity-QED and observe polariton formation in both attractive and repulsive branches: this constitutes a new regime of polaron physics where the polariton impurity mass is much smaller than that of the itinerant electrons. Their findings constitute a first step in investigation of a new class of degenerate Bose-Fermi mixtures consisting of polaritons and electrons.

We describe recent work at NIST to develop precision instruments based on atomic spectroscopy, advanced semiconductor lasers and micro-electro-mechanical systems (MEMS). These millimeter-scale instruments achieve take their high stability or sensitivity from the use of atomic spectroscopy, but have considerably reduced power consumption and potentially reduced manufacturing cost compared to their larger counterparts. Physics packages for atomic frequency references with fractional frequency stabilities in the range of 10-11 over one hour have been demonstrated. Using similar device designs and processing, magnetometers with sensitivities below 10 fT/Hz have been demonstrated, making them competitive with commercial SQUID-based sensors without the need for cryogenic cooling. The design, fabrication and performance of these instruments will be described, as well as a number of applications to which the devices are well-suited. Finally, we speculate on possible future directions for chip-scale atomic instrumentation with a focus on the use of laser-cooled atomic samples and tools for fundamental metrology.

Biography

Dr. John Kitching received his PhD. in Applied Physics from the California Institute of Technology in 1995. Since 2003, he has been a physicist in the Time and Frequency Division at NIST and currently is the Leader of the Atomic Devices and Instrumentation Group in NIST’s Physical Measurements Laboratory. His research interests include miniaturized atomic clocks and sensors and applications of semiconductor lasers and micromachining technology to problems in atomic physics and frequency control. Most recently, he and his group pioneered the development of microfabricated “chip-scale” atomic devices for use as frequency references, magnetometers and other sensors. He is a Fellow of NIST and has received a number of awards for his work including the Department of Commerce Silver and Gold Medals, the 2015 IEEE Sensors Council Technical Achievement Award, the 2016 IEEE-UFFC Rabi Award and the prestigious 2013 Rank Prize. He has published over 80 papers in refereed journals, has given numerous invited and plenary talks and has been awarded six patents.

The pursuit of increasingly sensitive interferometric measurement of mechanical motion has a rich history. This pursuit has resulted in the development and study of seminal ideas on quantum limits of measurement and how to improve measurements in the face of seeming limitations. In recent years, an interesting class of devices has been developed in which low-mass, high-frequency, and mechanically isolated objects are coupled to optical cavities. The large response of these mechanical objects to applied forces makes them an ideal platform to observe the effects of radiation forces. We can now cool mechanical membranes well into their quantum ground state and routinely observe the effect of a fluctuating radiation pressure force due to optical shot noise. Our recent measurements study a technique to improve interferometric displacement detection known as variational readout.

Trapped antimatter particles and atoms open the way to extremely precise comparisons of antimatter and matter - made to test the most fundamental symmetry of the Standard Model.

Atom interferometry in microgravity promises a major leap in improving precision and accuracy of matter-wave sensors [1]. When taking advantage of the unique space environment, fundamental tests challenging the state-of-the-art can be performed using quantum gases systems.

In this talk, we report on our recent progress in devising atom interferometery experiments to test Einstein’s equivalence principle at the 10-15 level or better [2] and detecting gravitational waves with high accuracy. Satellite mission scenarios achieving these goals will be presented.

The use of cold atoms as a source for such sensors poses; however, intrinsic challenges mainly linked to the samples size and mixture dynamics in case of a dual-atomic test. Proposals to mitigate leading systematics in projects involving extensive interferometry times are discussed in this talk as well. Novel methods of quantum engineering at lowest energy scales developed within the droptower experiments and sounding rocket missions are presented in this context [3-6].

References

[1] N. Gaaloul, et al. Proceedings of the International School of Physics "Enrico Fermi" Volume 188 (2014).

[2] D. N. Aguilera et al., Class. Quantum Grav. 31, 115010 (2014).

[3] T. van Zoest et al., Science 328, 1540 (2010).

[4] H. Müntinga et al., Phys. Rev. Lett. 110, 093602 (2013).

[5] J. Rudolph et al. New J. Phys. 17, 079601 (2015).

[6] S. Abend et al. Phys. Rev. Lett. 117, 203003 (2016).



Biography

Naceur Gaaloul is a researcher at the Institute of Quantum Optics, Leibniz University of Hanover, Germany since 2008 when he joined the group of Ernst Rasel and Wolfgang Ertmer. After an advanced diploma in fundamental physics in 2003, he moved to University Paris-sud where he pursued master and doctoral studies. In 2007, he obtained a doctoral title with a research thesis on theoretical manipulation of cold atoms with laser light. His main research focus at the moment is on dynamics of quantum gases in extended time offered by micro-gravity platforms. He is involved in several German, European and international space missions aiming to test fundamental theories of physics by performing atom interferometry experiments.

Abstract: In this talk I will discuss several examples of interesting universal dynamics with quantum simulation. In the first example, I will discuss an expansion dynamics of scale invariant quantum gases in a time-dependent harmonic trap, that displays a discrete temporal scaling symmetry, and we term it as “ the Efimovian expansion”. This dynamics reveals the scaling symmetry and the emergent conformal symmetry of strongly interacting quantum system. In the second example, I will discuss quench dynamics from a topological trivial Chern insulator to a topological nontrivial one, and we show how to extract a quantized value from the quench dynamics, that exactly equals to the topological Chern number of the final Hamiltonian after the quench. In the third example, I will prove a theorem that relates the entropy growth after a quench to the out-of-time-ordered correlation that recently discussed in the content of quantum chaos and holographic duality. This three examples reveal the interplay between quantum dynamics with symmetry, topology and entropy, respectively.
[1] Shujin Deng, Zhe-Yu Shi, Pengpeng Diao, Qianli Yu, Hui Zhai, Ran Qi and Haibin Wu, Science, 353, 371 (2016)
[2] Ce Wang, Pengfei Zhang, Xin Chen, Jinlong Yu and Hui Zhai, arXiv: 1611.03304
[3] Ruihua Fan, Pengfei Zhang, Huitao Shen and Hui Zhai, arXiv: 1608.01914
[4] Jun Li, Ruihua Fan,

March 13-15, 2017
Olympic Valley, CA

Stanford University Physics Department AMO groups
Prof. Mark Kasevich research group
Prof. Monika Schleier-Smith research group
Prof. Jason Hogan research group

The number of biological macromolecules with a structure solved by cryogenic-electron microscopy (cryo-EM) increases dramatically each year. However, many small and weakly scattering protein structures remain out of reach, as electron dose induced specimen damage limits the achievable spatial resolution [1].
Improved sensitivity and spatial resolution can be obtained employing quantum measurement strategies. A quantum optimal approach to measuring small phase shifts, as induced by a thin protein, is to pass each probe particle through the specimen multiple times [2].
Employing self-imaging cavities, this idea can be applied to widefield microscopy [3]. We show post-selected optical birefringence and absorption measurements beyond the shot-noise limit and discuss the applicability of multi-pass microscopy to cryo-EM. Our EM simulations [4] show that multi-pass TEM allows for a tenfold damage reduction in imaging small proteins.

[1] Glaeser et al, Nat. Methods, 13, 1, 28-32 (2016).
[2] Giovannetti et al., Physical Review Letters 96, 10401 (2006).
[3] Juffmann et al, Nature Communications 7, 12858 (2016).
[4] Juffmann et al, arXiv:1612.04931 (2016).

More than 30 years ago, Richard Feynman outlined the visionary concept of a quantum simulator for carrying out complex physics calculations. Today, his dream has become a reality in laboratories around the world. In my talk I will focus on the remarkable opportunities offered by ultracold quantum gases trapped in optical lattices to address fundamental physics questions ranging from condensed matter physics over statistical physics to high energy physics with table-top experiment.

For example, I will show how it has now become possible to image and control quantum matter with single atom sensitivity and single site resolution, thereby allowing one to directly image individual quantum fluctuations of a many-body system, to directly reveal antiferromagnetic order in the fermionic Hubbard model or hidden ‘topological order’. I will also show, how recent experiments with cold gases in optical lattices have enabled to realise and probe artificial magnetic fields that lie at the heart of topological energy bands in a solid, including Thouless charge pumps in multiple dimensions. Finally, I will discuss our recent experiments on novel many-body localised states of matter that challenge our understanding of the connection between statistical physics and quantum mechanics at a fundamental level.

Recent theoretical work has uncovered surprising richness in the dynamics of strongly interacting quantum systems, defining new classes of dynamics ranging from many-body localization to maximally chaotic behavior. This progress has highlighted fundamental open questions including, for example, the nature of the many body localization phase transition as well as the relation between quantum chaos and hydrodynamic modes in thermalizing systems. In this talk I will focus on how experiments with ultra-cold atoms can help address some of these questions. First, I will review recent progress in confronting the emerging theoretical picture of the MBL phase and phase transition with experimental tests. Then, I will turn to describe a new approach to compute the long time dynamics of thermalizing systems using tensor networks, allowing to compute both hydrodynamic transport properties and characteristics of quantum chaos. I will discuss proposals to test these results in experiments.

Ultracold quantum gases in optical lattices provide a unique platform for the study of tailored many-body systems. The realization of quantum gas microscopes marked a new era in this field. They enabled the precision detection of single atoms on individual lattice sites and with this provide direct experimental access to non-local correlation functions. Here we summarize the experimental progress with this new platform, where experiments evolved from textbook like studies in conceptually simple settings towards precisely controlled studies in computationally inaccessible regimes. We discuss recent results on many-body localization in two dimensions as well as on string correlations in Fermi-Hubbard chains.

Reaching dual superfluidity in helium mixtures has long been one of low-temperature physics holy grails . However, this long sought goal has been thwarted by the repulsive interactions between the two isotopes that leads to their demixion at low temperature. In ultracold atoms, the possibility offered by Feshbach resonances of tuning the strength of interatomic interactions has allowed us to cool a mixture of 6Li and 7Li into a regime where the mixture is stable and both species are superfluid. We have proved their superfluid behaviour by creating a counterflow between the two species. We have demonstrated the existence suggesting the existence of a novel damping mechanism generalizing Landau's scenario to superfluid mixtures.
More recently, we have shown that probing the inelastic decay of the mixture could be used as a quantitative probe of the short range correlation of a many-body system.

Ultracold atomic physics experiments offer a nearly ideal context for the
investigation of quantum systems far from equilibrium. I will present results
from two experiments investigating driven quantum gases. The first
experiment aims to realize a nontrivial Floquet phase of matter in a strongly
amplitude-modulated optical lattice. The new phase can be understood as a
many-body quantum-mechanical analogue of an inverted Kapitza pendulum.
The second experiment uses trapped degenerate strontium as a quantum
emulator of ultrafast atom-light interactions. Here the low energy scales of cold
atom experiments give rise to an effective temporal magnification factor of
eleven orders of magnitude, enabling the study of nonequilibrium dynamics
relevant to attosecond-scale electronic phenomena.

Physics/AP Colloquium
Many-body quantum systems are very hard to describe, since the number of parameters required to describe them grows exponentially with the number of particles, volume, etc. This problem appears in different areas of science, and several methods have been developed in fields of quantum chemistry, condensed matter and high energy physics in order to circumvent it in certain situations. In the last years, other approaches inspired by quantum information theory have been introduced in order to address such a problem. On the one hand, quantum simulation uses a different system in order to emulate the behavior of the problem under study. On the other, tensor networks aim at the accurate description of many-body quantum states with few parameters. In this talk, I will give a basic introduction to those approaches, and explain current efforts to use them in order to attack both condensed and high-energy physics problems.

Juan Ignacio CIRAC
Director of Theory Division, Max Planck Institute of Quantum Optics, Garching, Germany
Born in Manresa, Spain. In 1988, he graduated in Theoretical Physics from the Complutense
University, Madrid, and gained his PhD in 1991. Between 1991 and 1996, he was Associate
Professor at the University of Castilla-La Mancha, and spent long visits at the University of
Colorado and at Harvard University. From 1996 until 2001 he was Professor of Theoretical Physics
at the University of Innsbruck, Austria. He is a member of the Max Planck Society since 2001, the
year when he was appointed director at the Max Planck Institute of Quantum Optics (Garching,
Germany). In 2002 he also became honorary professor at the Technical University of Munich.
As an expert in quantum computation and its application in the field of information, the focus of his
research work is the quantum theory of information. His theories propose that quantum computers
will bring a new revolution to the field of information, and will lead to more efficient
communication and far greater security in data processing and transmission.
He is a member of the Spanish Academy of Sciences, and corresponding member of the Austrian,
Zaragoza, and Barcelona Academies, as well as fellow of the American Physical Society. Cirac’s
work has obtained many awards, including the Felix Kuschenitz Prize at the Austrian Academy of
Sciences in 2001, the Quantum Electronics from the European Science Foundation in 2005, the
Prince of Asturias Prize for Scientific and Technical Research in 2006, the National "Blas Cabrera"
Prize for Physical, Material and Earth Sciences in 2007, the Frontiers of Knowledge and Culture
Award for basic science given by the BBVA Foundation in 2008, the 2010 Franklin Medal, the
2013 Niels Bohr Medal, the Wolf Foundation Prize in Physics in 2013 and, more recently, the
Hamburger prize for Theoretical Physics. He holds a honorary degree from the universities of
Castilla-La Mancha, Politécnica de Barcelona, Zaragoza, Valencia, Politécnica de Valencia, and
Europea de Madrid.

Trapped ensembles of neutral atoms can be cooled to nanoKelvin temperatures to form pristine material with which to model complex quantum systems and build new ones for fundamental physics and applications. For example, strongly-interacting fermions, that govern the physics of high-temperature superconductors and neutron stars, may be explored in the lab using an ultracold gas of lithium atoms. By combining ultracold atomic gases of two different elements (ytterbium and lithium), we realize a mixture of Bose and Fermi superfluids, a system out of reach with liquid helium mixtures. We demonstrate elastic coupling and observe angular momentum exchange between the superfluids. We will also report on the development of a Bose-Einstein condensate interferometer using optical standing waves, with the long-range goal of measuring the fine-structure constant and testing quantum electrodynamics. We observe phase-stable fringes for large (>100 photon recoil momenta) interferometer arm separation. The sensitivity of the interferometer to diffraction phases could be applied towards studying atomic band structure in optical lattices.

In Einstein's general theory of relativity, time depends locally on gravity; in standard quantum theory, time is global - all clocks “tick” uniformly. In my talk I will present our demonstration of a new tool for investigating time in the overlap of these two theories: a self-interfering clock, comprising two atomic spin states. We prepare the clock in a spatial superposition of quantum wave packets, which evolve coherently along two paths into a stable interference pattern. If we make the clock wave packets “tick” at different rates, to simulate a gravitational time lag, the clock time along each path yields “which path” information, degrading the pattern's visibility. By contrast, in standard interferometry, time cannot yield “which path” information. This proof-of-principle experiment may have implications for the study of time and general relativity and their impact on fundamental effects such as decoherence and the emergence of a classical world. Time permitting, I will also present preliminary results regarding realization of a complete Stern-Gerlach interferometer.

Floquet engineering is an important tool for the engineering of novel band structures with interesting properties that go beyond those offered by static systems. Recently, Floquet systems have enabled the generation of Bloch bands with non-trivial topological properties, such as the Hofstadter and Haldane model. This led to the observation of chiral Meissner currents and the first Chern-number measurement with charge-neutral atoms.<br><br>Besides this success studies of many-body phases in driven systems remain experimentally challenging in particular due to the interplay between periodic driving and interactions. In a driven system energy is not conserved which can lead to severe heating. In order to find stable parameter regimes for the generation of driven many-body phases it is essential to develop a deeper understanding of the underlying processes.<br><br>In this talk, I briefly review recent experimental advances in the generation of topological band structures in the non-interacting regime using Floquet engineering and present first studies of interacting atoms in driven 1D lattices.<br><p><span></span></p>

The accuracy of atomic clocks has improved a thousandfold over the last 15 years, driven by improvements in ultrastable lasers, quantum control, and our understanding of atomic interactions. The latest generation of optical lattice clocks are accurate and precise enough to measure general relativity's gravitational redshift at the millimeter scale, to test physics beyond the Standard Model, and to reveal new emergent properties of quantum materials. In this talk, I will discuss a next-generation clock that probes degenerate fermions in a three-dimensional optical lattice. By controlling atomic interactions and light shifts, this apparatus achieves a record atom-light coherence time of six seconds and a precision of 2.5 parts in 10^19. Finally, if time allows, I will discuss a search for ultralight dark matter with our newfound precision.

<p><span>After almost two-decades of sustained effort in making spin-based qubits, silicon still has great promise as the technology of choice for future quantum computers. After a brief update on the field, I will discuss our recent work proposing new qubit and coupling approaches for silicon quantum dots that attempt to overcome the biggest challenges facing construction of a silicon quantum computer. I will end by discussing what semiconductor and superconducting qubit designers can learn from each other and other promising new research directions.<span></span></span></p><p align="center"><b><span><span> </span></span></b></p>

<br><p></p><p><span>March 19-21, 2018</span></p><p><span>Olympic Valley, CA</span></p><p></p><p><b><span>Monday, March 19th</span></b></p><p><span> 9:30-12:30pm Arriving & Registration</span></p><p><span>·12:30 pm Lunch Break</span></p><p><span>·1:30 pm Introduction toEach AMOExperiment in the Groups</span></p><p><span>·3:00-6:00pm Intergroupquestion andidea exchange for each experiment</span></p><p><span>·7:00 pm Dinner at AuldDubliner</span></p><p></p><p><b><span>Tuesday, March 20th</span></b></p><p><span>9:30-12:30pm Free discussion</span></p><p><span>·12:30pm:  Lunch atGold Coast</span></p><p><span>·2:00-3:00 pm EquivalencePrincipalDiscussion</span></p><p><span>·3:00-6:00 pm Interteamsmall groupdiscussion</span></p><p><span>·6:30pm Dinner atFireside Pizza</span></p><p></p><p></p><p></p><p><span>Participant: </span></p><p><span>Mark Kasevich</span></p><p><span>Jason Hogan</span></p><p><span>David Berryrieser</span></p><p><span>Brannon Klopfer</span></p><p><span>Benjamin Pichler</span></p><p><span>Yunfan Wu</span></p><p><span>Remy Nortermans</span></p><p><span>Yehonatan Israel</span></p><p><span>Julian Martinez</span></p><p><span>Chris Overstreet</span></p><p><span>Tim Kovachy</span></p><p><span>Peter Asenbaum</span></p><p><span>Robin Corgier</span></p><p><span>Thomas Wilkason</span></p><p><span>Jan Rudolph</span></p><p><span>Hunter Swan</span></p><p><span>Ben Garber</span></p>

<b class="">Mechanical oscillators coupled to light via the radiation pressure force have attracted significant attention over the past years for allowing tests of quantum physics with massive objects and for their potential use in quantum information processing. Recently demonstrated quantum experiments include entanglement and squeezing of both the mechanical and the optical mode. So far these quantum experiments have almost exclusively operated in a regime where the light field oscillates at microwave frequencies. Here we would like to discuss recent experiments where we demonstrate various non-classical mechanical states by coupling a mechanical oscillator to single optical photons. These results are a promising route towards using mechanical systems as quantum memories, for quantum communication purposes and as light-matter quantum interfaces.</b>

Physics/Applied Physics Colloquium

A central challenge in building a scalable quantum computer is the execution of high-fidelity entangling gates within an architecture containing many resonant elements. As elements are added, or as the multiplicity of couplings between elements is increased, the frequency space of the design becomes crowded and device performance suffers. By applying flux modulation to tunable transmons, one can drive the resonant exchange of photons directly between energy levels of a statically coupled multi-transmon system. This obviates the need for mediating qubits or resonator modes and allows the full utilization of all qubits in a scalable architecture. The resonance condition is selective in both the frequency and amplitude of modulation and thus alleviates frequency crowding. We discuss using these techniques to scale superconducting qubit processors to lattices containing 19 qubits and the results of initial hybrid quantum algorithms run on such processors.

Non-Abelian and non-adiabatic variants of Berry's phase have been pivotal in the recent advances in holonomic quantum gates, while Berry's phase itself is at the heart of the study of topological phases of matter. Here we use ultracold atoms to study the unique properties of spin-1 geometric phase [1]. The spin vector of a spin-1 system, unlike that of a spin-1/2 system, can lie anywhere on or inside the Bloch sphere representing the phase space. This suggests a generalization of Berry's phase to include closed paths that go inside the Bloch sphere. In [2], this generalized geometric phase was formulated as an SO(3) operator carried by the spin fluctuation tensor, developing on the m=0 spin geometric phases [3] . Under this generalization, the special class of loops that pass through the center, which we refer to as singular loops are significant because their geometrical properties are qualitatively different from the nearby non-singular loops, making them akin to critical points of a quantum phase transition. Here we use coherent control of ultracold 87Rb atoms in an optical trap to experimentally explore the geometric phase of singular loops in a spin-1 quantum system [1].


[1] H. M. Bharath, M. Boguslawski, M. Barrios, Lin Xin and M. S. Chapman, arXiv:1801.00586 (2018), link: https://arxiv.org/abs/1801.00586
[2] H. M. Bharath, arXiv:1702.08564 (2017), link: https://arxiv.org/abs/1702.08564
[3] J. M. Robbins, M. V. Berry, Journal of Physics A: Mathematical and General 27, L435 (1994), link: http://iopscience.iop.org/article/10.1088/0305-4470/27/12/007/meta

Individual atoms are standards for quantum information technology, acting as qubits that have unsurpassed levels of quantum coherence, can be replicated and scaled with the atomic clock accuracy, and allow near-perfect measurement. Atomic ions can be confined by silicon-based chip traps with lithographically-defined electrodes under high vacuum in a room temperature environment. Entangling quantum gate operations can be mediated with control laser beams, allowing the qubit connectivity graph to be reconfigured and optimally adapted to a given algorithm or mode of quantum computing. Existing work has shown >99.9% fidelity gate operations, fully-connected control with up to about 10 qubits, and quantum simulations with over 50 qubits. I will speculate on combining all this into a single universal quantum computing device that can be co-designed with future quantum applications and scaled to useful dimensions.

Recently realized single-atom array synthesizers have drawn much attention on the field of atomic physics regarding quantum simulation because defect-free single-atom array suitable for spin-lattice simulation would be quickly formed [1]. Subsequently, their capacities as Rydberg quantum simulators have been demonstrated as well [2]. In this talk, I will introduce mainly my results on the array synthesizer and proof-of-principle quantum simulation thereof.
In the first part, I will report on how defect-free single-atom array could be prepared by using a liquid-crystal spatial light modulator. Further performance improvement for speed, scale, and dimension will be discussed as well.
In the second part, an experimental result on thermalization dynamics of Ising-like spin-1/2 chain will be presented. The defect-free linear or zig-zag chains of up to N=25 atoms were formed for the experiment. Then, we suddenly quenched 480 nm and 780 nm lasers for two-photon Rydberg excitation. The Rydberg fraction showed dynamics toward an equilibrium that was predicted by a thermalization theory. Also, the microscopic principle of the thermalization (detailed balance between spin-flip) was observed. It is worth to note that this thermalization scenario is a natural consequence of mere Schroedinger equation, rather than a result of an assumption such as connection to a thermal bath. Also, I will discuss the eigenstate thermalization hypothesis in this system.

[1] H. Kim, et al., "In situ single-atom array synthesis using dynamic holographic optical tweezers," Nature Communications 7, 13317 (2016);
M. Endres, et al., "Atom-by-atom assembly of defect-free one-dimensional cold atom arrays," Science 354, 1024-1027 (2016); D. Barredo, et al., "An atom-by-atom assembler of defect-free arbitrary two-dimensional atomic arrays," Science 354, 1021-1023 (2016).
[2] H. Kim, et al., "Detailed Balance of Thermalization dynamics in Rydberg atom quantum simulators,"
Physical Review Letters 120, 180502 (2018);
H. Bernien, et al., "Probing many-body dynamics on a 51-atom quantum simulator," Nature 551, 579 (2017);
V. Lienhard, et al., "Observing the space- and time-dependent growth of correlations in dynamically tuned
synthetic Ising antiferromagnets," arXiv:1711.01185 (2017).

The physics of out-of-equilibrium quantum many-particle systems underlies the behavior of important existing and emerging technologies. Better understanding and controlling these dynamics both involves interesting foundational research, and is likely to have a key role in the development of future generations of quantum technologies. Recent advances in experiments have made it possible to control and engineer dynamics, not only of closed quantum systems, but also in open many-body quantumsimulators. In this meeting, we will bring together experiment and theory of out-of-equilibrium dynamics in open quantum simulators, as well as representatives from industry, in order to develop new collaborations and set a platform for future advances in this area.

https://photonics.stanford.edu/events/dynamics-and-dissipation-quantum-simulation-workshop

Quantum devices could perform tasks with much better performances than classical systems, with profound implications for cryptography, chemistry, material science, and many areas of physics. However, to reach this goal we need to control large quantum systems, where the many-body dynamics becomes often fragile and very complex.

Among the many questions and challenges that arise when working toward this goal, I will address two questions in my talk: How does a close quantum system thermalize (thus losing its “quantum power”)? How can we preserve quantum information in the presence of strong interactions?

Using a nuclear spin chain as an exemplary experimental system, and the tools of Hamiltonian engineering, I will show how spin chains can transport information and entanglement. I will then show how disorder can quench the transport of information, a phenomenon known as localization. This phenomenon might actually be a feature in some situations, as it allows preserving local quantum information for later retrieval and prevents thermalization. Is localization however possible even in the presence of long-range interaction? I will show experimental signatures that a logarithmic growth of long-range correlation is still present in interacting systems, a sign of many-body localization. I will further discuss how metrics of information scrambling such as out-of-time ordered correlations can be used to distinguish thermalization from the long-time equilibrium phase of prethermalization.

The isolated, clean, and tunable nature of ultracold gases make them a natural platform for
controlled realization and study of Floquet physics and driven quantum systems. I will present recent results from the Weld group discussing three experiments along these lines. First I will discuss an ultracold strontium experiment in which weak driving of a bichromatic lattice is used to probe novel excitation spectra in quasiperiodic systems. I will then talk about ultracold lithium in strongly modulated optical lattices, including the mapping of a Floquet phase diagram and exploration of a Floquet prethermal state. Finally, I will present results from a new type of quantum simulator in which a driven Bose condensate of strontium emulates ultrafast ionization dynamics in attosecond laser pulses, counter-intuitively enabling the study of some of the fastest processes in atomic physics with some of the slowest.

I will describe superradiant pulses of light generated from an optical transition that does not normally like to radiate light: the millihertz linewidth optical transition in strontium. This new source of light may allow us to break through long standing thermal and technical limitations on laser frequency stability. The pulses of light are generated by laser cooling and trapping an ensemble of strontium atoms inside a high finesse optical cavity to achieve a large collective enhancement in the radiation rate. We also observe cavity-mediated spin-exchange interactions that manifest as one-axis twisting dynamics and the opening of a many-body energy gap. The spin-exchange interactions may prove useful for creating entanglement between the atoms and enhancing atomic coherence times.

Alkaline earth atoms like strontium have a rich internal structure, including optical transitions with narrow and ultranarrow linewidths. This enables a wealth of possibilities for precision metrology and quantum science. In this talk, I will present experimental studies of three research directions enabled by these transitions. I will present the first studies of superradiant emission from the 1 millihertz linewidth optical clock transition in an ensemble of strontium atoms confined within an optical cavity. This system holds promise as a new form of high-precision active optical frequency reference with the potential to operate outside of carefully controlled laboratory environments, and exhibits interesting spin-exchange dynamics mediated by optical photons. Next, I will describe a new form of laser cooling based on narrow-linewidth optical transitions that has reduced reliance on spontaneous emission compared to traditional Doppler cooling. This feature may make it suitable for the cooling of molecules, for which spontaneous emission presents significant challenges. Finally, I will discuss recently demonstrated microscopic control of individual strontium atoms confined within optical tweezers. By combining the potential for flexible, low-entropy state preparation and high-fidelity, single-particle state readout associated with optical tweezers with the rich internal structure of strontium, this platform has promising applications for quantum simulation and metrology.

I will describe our recent results on optical trapping, laser cooling and imaging of CaF molecules, the laser cooling of SrOH molecules, and the prospects for laser cooling of larger polyatomic molecules. I also will present recent progress in the field of electron electric dipole moment searches using heavy diatomic molecules, in particular the recent ACME result, and future prospects, including the use of polyatomic molecules.

In recent years, optically probed nitrogen–vacancy (NV) quantum defects in diamond have become a leading modality for magnetic, electrical, and temperature sensing at short length scales (nanometers to millimeters) under ambient conditions. This technology has wide-ranging application across the physical and life sciences — from NMR spectroscopy at the scale of individual cells to improved biomedical diagnostics to the search for dark matter. I will provide an overview of quantum diamond sensors and their diverse applications.

In this talk I will describe our ongoing effort at the University of Chicago to explore exotic models of condensed matter using materials made of light. Starting with a quick discussion of "light as matter,” I will then explain how we imbue photons with the essential attributes of a material particle: mass, charge, and interactions. Along the way, I will introduce the two “flavors” of photons that we employ for our photonic matter: optical photons trapped in Fabry-Perot cavities, and microwave photons trapped in superconducting resonators or transmon qubits. Finally, I will describe the first two materials that have emerged from our interacting photons: a Mott insulator of microwave photons and a topological fluid of optical photons. More broadly, building materials from light impacts both (a) the kinds of matter that can be assembled, and (b) the assembly process itself, providing a new window on the physics of correlated quantum matter.

Quantum simulations based on laser-cooled atomic gases have started to fulfill Feynman's vision of using well controlled quantum systems to obtain insight into problems which are hard to tackle on classical computers. Key to the success of ultracold atoms is the continuous development of novel methods to prepare, control and detect such systems. In this talk, I will focus on how long-range interactions can be added to the toolbox available in ultracold atomic quantum simulators.

Starting from an array of Rubidium-87 atoms trapped in an optical lattice, we realize long-range interacting spin models by laser coupling the atomic ground state to a Rydberg state. Combining single-atom sensitive local detection with interferometric techniques, we verified the presence of interactions and demonstrated their controllability. Tracking the collapse and revival dynamics of a coherent spin state, we could furthermore show that the coherence time of off-resonantly admixed interactions can be pushed towards the tunneling timescale in optical lattices, paving the way to engineering extended-range interactions in systems with motional dynamics in the future.

In a further experiment, we were able to observe a novel form of bound molecular state of two atoms simultaneously excited to their Rydberg states. Remarkably, the bond length of such "Rydberg macrodimers" reaches up to the micrometer scale and is hence accessible in a quantum gas microscope. The high spectral resolution of our measurement combined with microscopic readout enabled a precise characterization of the binding potential as well as the photoassociation pathway.

Finally, I will present our ongoing experimental efforts of using a high-finesse optical resonator to control the atom number in an ensemble. The real-time signal output of the cavity can be used for active feedback on an optical evaporation stage, allowing for the production of atomic ensembles with sub-Poissonian shot-to-shot atom number variation.

<a href="https://sites.google.com/view/2019bacam&quot; id="ow1036" __is_owner="true">https://sites.google.com/view/2019bacam</a&gt;

Whether quantum correlations between identical particles can serve as a resource for
quantum information has often been questioned, since the constituent particles are not
individually addressable. In this talk, I will present a scheme for converting these correlations
into entanglement between distinct spatial modes. Starting with a Bose-Einstein
condensate (BEC) of 87Rb in a tightly confining trap, we use spin-mixing to generate
a quantum correlated state of indistinguishable particles in a single spatial mode. This
entanglement is subsequently distributed in space by expanding the atomic cloud. Using
a spatially resolved spin readout we demonstrate a particularly strong form of entanglement
known as Einstein-Podolsky-Rosen (EPR) steering between spatially distinct
regions of the expanded BEC. This certifies that the prepared state is indeed a useful
resource for quantum information protocols. Additionally, we developed a new readout
technique based on the extension of the Hilbert space which enables the simultaneous
and spatially resolved extraction of multiple conjugate observables. We show that this
technique is capable of detecting quantum correlations by measuring fluctuations below
the standard quantum limit.

Atomic spins are natural carriers of quantum information given their long coherence time and our capabilities to coherently control and measure them with magneto-optical fields. In this seminar I will describe two paradigms for quantum information processing with ensembles of spin in cold atoms. The strong electric dipole-dipole interactions arising when atoms are excited to high-lying Rydberg states is a powerful method for designing entangling interactions in neutral atoms. I will explore how adiabatic dressing of ground-state atoms with high-lying Rydberg states provides an avenue for further manipulation of nonclassical states based on the techniques of optimal control. By mapping a symmetrically-coupled Rydberg ensemble to the Jaynes-Cummings model, I will show how we can obtain arbitrary control of superpositions of collective Dicke states. Moreover, adiabatic dressing and quantum control can allow us to create high-fidelity entangling two-qubit gates, robust to random atomic motion at finite temperature, and other imperfections. In a second paradigm, atoms can be entangled through their mutual coupling to a common mode of the quantum electromagnetic field which acts as a quantum data bus. I will show how one can use this quantum data bus for measurement-based feedback to simulate nonlinear dynamics, quantum chaos, the quantum-to-classical transition, and quantum simulations of quantum many-body-dynamics.

Abstract: Attempts to construct quantum computers from trapped atomic ions have focused almost exclusively on naturally-abundant isotopes of hydrogen-like species. Now that we understand the limitations of this approach, it is time to explore species and structure beyond this model and how they may help solve some of the problems haunting existing efforts. I will discuss some of the promising new directions that can be taken with synthetic isotopes, metastable species, and polar molecular ions.

<p>Predicting the evolution of many-body systems under attractive interactions is a challenging</p><p>ask, owing to the instability to collapse. Bright solitons are remarkable stationary states, established when the self-focusing effect responsible for collapse is exactly compensated by wave dispersion. In two-dimensional (2D) Bose gases, however, such intricate balance cannot e fulfilled except at a critical norm known as the Townes threshold – only at which matter-wave right solitons can form. In this talk, I will discuss our recent study on the collapse dynamics in a omogeneous 2D Bose gas (formed by atomic cesium), when its interaction is quenched from epulsive to attractive via a Feshbach resonance [1]. We observe the formation of Townes solitons hrough the manifestation of modulational instability that results in the amplification of density wave disturbances and fragmentation of a 2D sample. Our high-resolution density measurements n space and time domain reveal detailed information about the formation process, from the amplified growth of density waves, the formation of 2D solitons, to the subsequent collision and collapse dynamics, demonstrating multiple universal behaviors in association with the formation f a stationary state. Towards the end of the talk, I will discuss our on-going plan for exploring on-equilibrium dynamics such as quantum critical transport, entanglement generation and istribution in a strongly-coupled 2D gas loaded in an optical lattice and with spatiotemporal control of atomic interactions.</p><p><br></p><p></p><p>1] Cheng-An Chen and Chen-Lung Hung, arXiv:1907.12550 (2019).</p>

<p>Of the wide variety of sophisticated techniques employed inoptical microscopy, of special interest to physicists are schemes which usequantum correlations to increase sensitivity beyond the classical limit. Suchtechnology would be especially applicable in transmission electron microscopy(TEM) since the image resolution of samples of critical interest (e.g.proteins, polymers, and battery materials) is limited by beam damage. However,in contrast to the fantastic diversity and modularity of light optics, electronoptics are significantly constrained. I will describe our project of developingnew electron optics to enable dose-efficient TEM. While quantum metrology isgenerally associated an entangled probe (which has not yet been demonstratedwith free-space electrons), it is also possible to perform quantum-optimalmeasurements with a single particle using sequential measurements [1]. In fact,it is possible to gain significant information about absorbing samples usingonly damage-free counterfactual measurements [2]. More typically, TEM samplesare phase objects. We have shown that an approach called Multi-Pass TEM (MPTEM)could reduce damage by an order of magnitude for realistic samples [3]. Theykey new electron optics of the MPTEM are the switchable mirrors, which trapelectrons in a cavity where the sample is re-imaged multiple times. We arecurrently building a 10 keV MPTEM [4] as a proof of concept.</p><p> </p><p>[1] Quantum Metrology,Vittorio Giovannetti, Seth Lloyd, and Lorenzo Maccone, PRL 2006</p><p>[2] Designs for a Quantum Electron Microscope, P. Kruit etal, Ultramicroscopy 2016</p><p>[3] Multi-Pass transmission electron microscopy, T.Juffmann et al, Scientific Reports, 2017</p><p>[4] Design for a 10keV Multi-Pass Transmission Electronmicroscope, S. A. Koppell, Ultramicroscopy 2019</p>

Quantum information processing with neutral atoms offers a path towards scalable assembly of large qubit registers, with the potential for hundreds of individually controlled qubits in near term systems. Interactions between atoms can be switched on by coupling the atoms to highly excited Rydberg states. We demonstrate two techniques for engineering entanglement in such neutral atom systems. In the first, we perform a universal two-qubit gate, and achieve a new record for neutral atoms of 97.4% gate fidelity. In the second, we create a fully entangled Schrödinger cat state with up to 20 atoms by employing both local qubit addressing as well as optimal control techniques to achieve fast state preparation. These results highlight the potential of neutral atom systems for high-fidelity quantum information processing.

The remarkable success of atom coherent manipulation techniques has motivated competitive research and development in precision metrology. Matter-wave inertial sensors – accelerometers, gyrometers, gravimeters – based on these techniques are all at the forefront of their respective measurement classes. Atom inertial sensors provide nowadays about the best accelerometers and gravimeters and allow, for instance, to make the most precise monitoring of gravity or to device precise tests of the weak equivalence principle (WEP). I present here some recent advances in these fields:
The outstanding developments of laser-cooling techniques and related technologies allowed the demonstration of an airborne matter-wave interferometers, which operated in the micro-gravity environment created during the parabolic flights of the Novespace Zero-g aircraft. Using two atomic species (for instance 39K and 87Rb) allows to verify that two massive bodies undergo the same gravitational acceleration regardless of their mass or composition, allowing a test of the Weak Equivalence Principle postulated by Einstein.
New concepts of matter-wave interferometry can also be used to study the low frequency variations of the strain tensor of space-time and gravitation. For instance, the MIGA instrument, which is currently built in the underground laboratory in Rustrel, France will allow the monitoring of the evolution of the gravitational field at unprecedented sensitivity, which will be exploited both for geophysical studies and for Gravitational Waves (GWs) observations.

The QCD axion, which solves the strong CP problem in QCD, is one of the best motivated dark-matter candidates. I will discuss efforts to develop electromagnetic searches for QCD axion dark matter with masses below 1 micro-eV, including the Dark Matter Radio Cubic Meter experiment, which will probe the QCD axion band over 1.5 orders of magnitude in axion mass. However, full coverage of the QCD axion band will not be possible without acceleration by using quantum measurement techniques, which can be used to evade the standard quantum limit by the exploitation of quantum correlations in the electromagnetic signals. While photon counting is a useful technique to evade the SQL at masses above 1 micro-eV, it is not a useful technique at lower mass ranges. I will describe Quantum Upconverters, which convert signals from DC up to ~300 MHz to the microwave frequency range. Quantum upconverters can be used to implement techniques including backaction evasion to outperform the Standard Quantum Limit at the RF frequencies probed by DM Radio. They can also be used to improve electromagnetic sensing of nuclear spins for NMR-based detection schemes (including CASPEr).

Stimulated emission is often described as indistinguishable from the stimulating beam, sharing the same phase, frequency, polarization, and direction of travel. What direction does stimulated emission travel when the emitter is pointlike? Pointlike sources typically emit in all directions (a spherical wave), but if the stimulating beam is nearly monodirectional (a plane wave), will the stimulated emission propagate in all directions, or just one? We perform simple experiments to explore this apparent paradox, with an eye towards technological utility. In particular, does stimulated emission encode information about an emitter's location? Can lenses use this stimulated emission to form images of emitter distributions? If so, this suggests a way to combine the high signal rates of transmitted light microscopy with the specificity of fluorescence microscopy.

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from. 

<br>As we have the last few weeks, we will host a post-seminar discussion session with the speaker. The discussion will take place in a separate Zoom room directly after the seminar, and all attendees are welcome to participate. (Faculty will be asked to leave after ~10-15 minutes to give students and postdocs more opportunities to interact with the speaker.) <br><br>An abstract for Manuel's talk, as well as the list of future seminars and the speaker nomination form, can be found on the VAMOS website: <a href="https://sites.google.com/stanford.edu/virtual-amo-seminar/home">https://sites.google.com/stanford.edu/virtual-amo-seminar/home</a&gt;. Please forward this email to anyone you think might be interested, and consider nominating a speaker you're interested in hearing from.