# Atomic Physics Seminar

*Institute for Advanced Study*

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atoms are excited into Rydberg states which are then tuned by the external electric field midway between two other Rydberg states of the opposite parity. The collective two-atom states are coupled by dipole-dipole interaction. We have proposed schemes of two-qubit gates using adiabatic passage of Forster resonances in time-dependent electric field. We have shown that radiofrequency electric fields can induce additional "inaccessible" resonances which are useful both for coherent coupling and for adiabatic passage. We have experimentally observed Borromean three-body Forster resonances for three interacting Rydberg atoms.

*Institute of Semiconductor Physics Novosibirsk, Russia*

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The first part of this talk discusses the general scheme of nEDM experiment with respect to the upcoming 2018 measurements at the Institut Laue-Langevin. The latter part will focus on optical Cs and Hg magnetometers used to monitor and stabilize the magnetic field.

*TUM Munich*

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make them attractive systems for the studies of ordered phases of interacting

many-body systems and simulating quantum phase transitions.

Several conceptually different approaches have been explored, both theoretically

and experimentally, for the preparation of crystalline order of Rydberg excitations

in spatially-extended ensembles of cold atoms. These include direct (near-)resonant

laser excitation of strongly-interacting Rydberg states in a two-dimensional lattice

gas, and adiabatic preparation of crystalline phases of Rydberg excitations in a

one-dimensional optical lattice by adiabatic frequency sweep of the excitation laser.

We show, however, that taking into account realistic relaxation processes affecting

the atoms severely complicates the prospects of attaining sizable crystals of Rydberg

excitations in laser-driven atomic media. Our simulations well reproduce the

experimental observations of spatial ordering of Rydberg excitations in driven

dissipative lattice gases, as well as highly sub-Poissonian probability distribution

of the excitation number. We find that the excitations essentially form liquid rather

than crystal phases with long-range order.

*Institute of Electronic Structure & Laser (IESL) Foundation for Research and Technology - Hellas (FORTH) Heraklion, Crete, GREECE*

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In this talk, I will discuss experimental strategies to control complex ions and molecules for which standard trapping, cooling and state manipulation methods fail. In particular, I will discuss how complex ions, such as Ti+ or Fe+, can be studied and used to place limits on the temporal variation of fundamental constants. Moreover, I will present a strategy to laser cool the diatomic molecule calcium monofluoride, a precursor to produce a degenerate dipolar quantum gas. Finally, I will show how strings of ions can be used to emulate processes relevant for transport phenomena in light harvesting processes.

I will conclude with a discussion on how to control and study two further quantum systems: electrons and aluminum chloride. Electrons can be stored in a novel two-frequency Paul trap, constituting the first step towards electron quantum computing; such a trap has, moreover, the potential to advance studies on matter-antimatter asymmetries by improving antihydrogen production. Furthermore, I will explain a laser cooling scheme for aluminum chloride, a molecule with excellent prospects for generating high phase-space density clouds at ultracold temperatures to study the physics of degenerate dipolar quantum gases.

*UC Berkeley*

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This talk will provide an introduction to how and why time is measured, with an emphasis on OLCs and their applications. I will discuss recent progress on pushing OLCs to even greater levels of precision, as well as prospects for future improvement. I also will present results from a recent experiment in which we harnessed the precision of an OLC to simulate complex condensed matter phenomena. Finally, I will give a brief overview of potential future applications of OLCs, including gravitational wave detection, tests of general relativity, and searches for physics beyond the Standard Model.

*JILA - University of Colorado Boulder*

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Advances in the control of light propagation and photon-photon interactions have lead to a new notion of photonic materials -- states of light that resemble material systems. I will describe our experimental approach to photonic materials, in which we use a degenerate non-planar optical resonator to realize a two-dimensional photon gas with an effective magnetic field. We observe photonic Landau levels, indicating a strong effective magnetic field, and a singularity of spatial curvature arising from the effectively conical geometry of our photon gas. Spatial curvature provides a novel probe of quantum Hall states, allowing us to make the first experimental measurement of the mean orbital spin, which characterizes topological phases. To realize photon-photon interactions, we demonstrate hybridization of photons in an optical resonator with atomic Rydberg excitations. Future work will investigate ordered states of interacting photons, including crystalline and fractional quantum Hall states.

*MIT*

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Single-photon cross phase shifts and other single-photon nonlinearities have numerous applications in all-optical quantum information processing. Several groups have experimentally achieved single-photon phase shifts on the order of pi. However, nonlinearities weaker than this have important applications as well. We introduce the idea of using metastable xenon gas in a high-finesse cavity to produce weak single-photon nonlinearities. This relatively simple and robust system avoids problems associated with the accumulation of alkali atoms on mirror surfaces, and is capable of approaching the strong coupling regime of cavity quantum electrodynamics. We demonstrate the feasibility of our approach with two proof-of-principle demonstrations, by measuring absorption saturation and cross-phase modulation using a cavity of moderately high finesse F=3,000. We find that the nonlinear effects occur at ultralow input power levels, proving that the presence of the cavity strongly enhances the inherent optical nonlinearities of metastable xenon. We close our discussion by reviewing our recent progress in building an improved cavity system, which is expected to produce enhanced single photon cross phase shifts.

*UMBC*

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I will describe the generation of 20dB spin-squeezed states of half a million 87Rb atoms inside of an optical cavity. From a practical point of view, the generated states enable up to a 100-fold reduction in required averaging times or atom numbers to achieve a given precision. I will explain the implementation of an atomic clock operating 10 dB beyond the standard quantum limit as well as the investigations of entanglement and Bell correlations in this system. I will then describe the demonstration of a new concept we call quantum phase magnification which utilizes optical cavity-aided interactions between atoms to magnify signals to-be-measured. This technique eliminates the need for low noise detection to achieve phase sensitivities beyond the standard quantum limit. I will conclude with future visions.

*stanford*

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