Arxiv Selection Feb 2020

Feb 1- Feb 7 Bhaskar Mukherjee, Feb 8- Feb 14 Zehan Li, Feb 15- Feb 21 Haiping Hu, Feb 22- Feb 28 Sayan Choudhury

Feb 14

arXiv:2002.05601 [pdf, other]

Collective Dissipative Molecule Formation in a Cavity

David Wellnitz, Stefan Schütz, Shannon Whitlock, Johannes Schachenmayer, Guido Pupillo

Comments: 12 pages, 4 figures

Subjects: Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph)

We propose a mechanism to realize high-yield molecular formation from ultra-cold atoms. Atom pairs are continuously excited by a laser, and a collective decay into the molecular ground state is induced by a coupling to a lossy cavity-mode. Using a combination of analytical and numerical techniques, we demonstrate that the molecular yield can be improved by simply increasing the number of atoms, and can overcome efficiencies of state-of-the-art association schemes. We discuss realistic experimental setups for diatomic polar and nonpolar molecules. This work exemplifies the opportunities for state engineering in cold molecules using collective cavity-couplings, especially in the presence of strong dissipation.

Feb 13

arXiv:2002.04812 [pdf, other]

Pattern formation and exotic order in driven-dissipative Bose-Hubbard systems

Zijian Wang, Carlos Navarrete-Benlloch, Zi Cai

Subjects: Quantum Gases (cond-mat.quant-gas)

Modern experimental platforms such as supercoducting-circuit arrays call for the exploration of bosonic tight-binding models in unconventional situations with no counterpart in real materials. Here we investigate one of such situations, in which excitations are driven and damped by pairs, leading to pattern formation and exotic bosonic states emerged from a non-equilibrium quantum many-body system. Focusing on a two-dimensional driven-dissipative Bose-Hubbard model, we find that its steady states are characterized by a condensation of bosons around momenta lying on a “Bose surface”, a bosonic analogue of the Fermi surface in solid-state systems. The interplay between instabilities generated by the driving, the nonlinear dissipative mode-coupling, and the underlaying lattice effect, allows the system to equilibrate into an exotic state of bosons condensed on a closed ring in momentum space instead of discrete points. Similar Bose liquid states have been discussed in the ground-state physics of strongly correlated systems. Here, we provide a route towards the robust dissipative preparation of this type of exotic states. Moreover, we provide a concrete ex- perimental implementation of our model in currently-available superconducting-circuit arrays. We also investigate the relaxation spectrum around the condensate, which shows a characteristic purely diffusive behavior.

Feb 12

arXiv:2002.04139 [pdf, other]

Jet Sub-structure in Fireworks Emission from Non-uniform and Rotating Bose-Einstein Condensates

Han Fu, Zhendong Zhang, Kai-Xuan Yao, Lei Feng, Jooheon Yoo, Logan W. Clark, K. Levin, Cheng Chin

Subjects: Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph)

We show that jet emission from a Bose condensate with periodically driven interactions, a.k.a. “Bose fireworks”, contains essential information on the condensate wavefunction, which is difficult to obtain using standard detection methods. We illustrate the underlying physics with two examples. When condensates acquire phase patterns from external potentials or from vortices, the jets display novel sub-structure, such as oscillations or spirals, in their correlations. Through a comparison of theory, numerical simulations and experiments, we show how one can quantitatively extract the phase and the helicity of a condensate from the emission pattern. Our work demonstrates the strong link between the jet emission and the underlying quantum system, which could shed light on the study of jet sub-structure in particle physics and high energy scattering experiments.

Feb 11

arXiv:2002.03051 [pdf, other]

Non-exponential decay in Floquet-Bloch bands

Alec Cao, Cora J. Fujiwara, Roshan Sajjad, Ethan Q. Simmons, Eva Lindroth, David M. Weld

Comments: 7 pages, 5 figures

Subjects: Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)

Exponential decay laws describe sys- tems ranging from unstable nuclei to fluorescent molecules, in which the probability of jumping to a lower-energy state in any given time interval is static and history-independent. These decays, in- volving only a metastable state and fluctuations of the quantum vacuum, are the most fundamental nonequilibrium process, and provide a microscopic model for the origins of irreversibility. Despite the fact that the apparently universal exponential decay law has been precisely tested in a variety of physi- cal systems [1], it is a surprising truth that quantum mechanics requires that spontaneous decay pro- cesses have non-exponential time dependence at both very short and very long times [2, 3]. Cold- atom experiments both classic [4] and recent [5] have proven to be powerful probes of fundamen- tal decay processes; in this paper, we propose the use of Bose condensates in Floquet-Bloch bands as a probe of long-time non-exponential decay in single isolated emitters. We identify a range of parameters that should enable observation of long- time deviations, and experimentally demonstrate a key element of the scheme: tunable decay between quasienergy bands in a driven optical lattice.