Seminar Schedule
Find upcoming seminars below. All talks are also announced via our mailing list and are also available via a google calendar (ical). Previous talks as well as a copy of the slides will be made available for the foreseeable future on the VIDEOS page.
Thu 20200709 17:00 CEST
Quantum Science Seminar #12: Quantum Reform of SI
JQI, NIST and University of Maryland
College Park — Maryland — U.S.A.
College Park — Maryland — U.S.A.
A New Measure: the quantum reform of the International System of Units
The metric system began with the French revolution,
with the lofty ideal that measurements would be tied
to the size of the earth, universally available to
all. Soon, practical considerations required units of
length and mass based on unique physical artifacts, a
nearantithesis to universal availability. Now we are
experiencing the greatest revolution in measurement
since the French revolution, a revolution rooted in
the atomic and quantum view of nature, again offering
universal availability. The definitions of the
kilogram, ampere, kelvin, and mole were all changed on
20 May 2019, and are now based on chosen and fixed
values for Planck’s constant, the quantum of electric
charge, Boltzmann’s constant, and Avogadro’s number. I
will explain how this is possible, why it was
necessary, and speculate about future changes in the
SI. In this context I will also discuss the role of
precision measurement in the history and future of
quantum physics.
Thu 20200716 17:00 CEST
Quantum Science Seminar #13: Quantum Computing
University of Virginia
Charlottesville — Virginia — U.S.A.
Charlottesville — Virginia — U.S.A.
Quantum computing over the rainbow: the quantum optical frequency comb as a platform for measurementbased universal quantum computing
An ultrafast laser emits vastly multimode light over a
broad spectral band, a.k.a. the optical frequency comb
(OFC), but the emission happens but one photon at a
time, if in a stimulated manner, and no entanglement
is created in the light. Changing the gain medium from
linear (onephoton) to nonlinear (twophoton) yields
an optical parametric oscillator which features
massively multipartite entanglement of the OFC modes,
as demonstrated experimentally by our group and
others. This entanglement can then be exquisitely
tailored to cluster states with specific graphs, in
particular the twodimensional ones that are universal
for measurementbased, oneway quantum computing. It
is worth noting that this requires only sparse
experimental resources that are highly compatible with
integrated optics, thereby paving the way to the
realization of practical quantum computers.
References

Continuousvariable quantum computing in the quantum optical frequency combJournal of Physics B: At. Mol. Opt. Phys.530120012020

Experimental realization of multipartite entanglement of 60 modes of a quantum optical frequency combPhysical Review Letters1121205052014

Entanglement gets scaled up in an optical frequency combPhysics Today64212011
Thu 20200723 17:00 CEST
Quantum Science Seminar #14: Atom Arrays
Laboratoire Charles Fabry, Institut d’Optique, CNRS
Palaiseau — France
Palaiseau — France
Manybody physics with arrays of individual atoms
This talk will present our effort to control and use
the dipoledipole interactions between cold atoms in
order to implement spin Hamiltonians useful for
quantum simulation of condensed matter situations [1].
We trap individual atoms in arrays of optical tweezers
separated by few micrometers. We create almost
arbitrary geometries of the arrays with unit filling
in two and three dimensions up to about 70 atoms. To
make the atoms interact, we either excite them to
Rydberg states or induce optical dipoles with a
nearresonance laser.
We have demonstrated the coherent energy exchange in chains of Rydberg atoms resulting from their resonant dipoledipole interaction. This interaction realizes the XY spin model and leads to the hopping a spin excitation from a site to another. We use this interaction to study elementary excitations in a dimerized spin chain featuring topological properties (SuSchriefferHeeger model). We have observed the edge states in the topological condition. We probed the regime beyond the linear response by adding several excitations, which act as hardcore bosons [2].
With optical dipoles, we explore light scattering in one dimensional chains of atoms. This system realizes a dissipative spin model, which could find applications in quantum optics to generate optical nonlinearities and nonclassical states of light [3].
We have demonstrated the coherent energy exchange in chains of Rydberg atoms resulting from their resonant dipoledipole interaction. This interaction realizes the XY spin model and leads to the hopping a spin excitation from a site to another. We use this interaction to study elementary excitations in a dimerized spin chain featuring topological properties (SuSchriefferHeeger model). We have observed the edge states in the topological condition. We probed the regime beyond the linear response by adding several excitations, which act as hardcore bosons [2].
With optical dipoles, we explore light scattering in one dimensional chains of atoms. This system realizes a dissipative spin model, which could find applications in quantum optics to generate optical nonlinearities and nonclassical states of light [3].
References

Observation of a symmetry protected topological phase of interacting bosons with Rydberg atomsScience3657752019

ManyBody Physics with Individually controlled Rydberg AtomsNature Physics161322020

Collective shift in resonant light scattering by a onedimensional atomic chainarXiv2004.05395 (Phys. Rev. Lett., in press)2020
Thu 20200730 17:00 CEST
Quantum Science Seminar #15: Quantum Dynamics
Observation of Dynamical Phase Transitions in Cold Atomic Gases
Nonequilibrium quantum manybody systems can display
fascinating phenomena relevant for various fields in
science ranging from physics, to chemistry, and
ultimately, for the broadest possible scope, life
itself. The challenge with these systems, however, is
that the powerful formalism of statistical physics,
which have allowed a classification of quantum phases
of matter at equilibrium does not apply. Therefore,
using controllable cold atomic systems to shed light
on the organizing principles and universal behaviors
of dynamical quantum matter is highly appealing. One
emerging paradigm is the dynamical phase transition
(DPT) characterized by the existence of a
longtimeaverage order parameter that distinguishes
two nonequilibrium phases. I will report the
observation of a DPT in two different but
complementary systems: a trapped quantum degenerate
Fermi gas and long lived arrays of atoms in an optical
cavity. I will show how these systems can be used to
simulate iconic models of quantum magnetism with
tunable parameters and to probe the dependence of
their associated dynamical phases on a broad parameter
space. Besides advancing quantum simulation our
studies pave the ground for the generation of
metrologically useful entangled states which can
enable real metrological gains via quantum
enhancement.
References