arXiv subjects

Kai-Xuan Yao

Publications and source records attributed to Kai-Xuan Yao.

5 recordsLinked to original sources

arXiv2022

Dynamical preparation of an atomic condensate in a Hofstadter band

The creation of a Hamiltonian in the quantum regime which has non-trivial topological features is a central goal of the cold-atom community, enabling widespread exploration of novel phases of quantum matter. A general scheme to synthesize such Hamiltonians is based on dynamical modulation of optical lattices which thereby generate vector potentials. At the same time the modulation can lead to heating and serious difficulties with equilibration. Here we show that these challenges can be overcome by demonstrating how a Hofstadter Bose-Einstein condensate (BEC) can be dynamically realized, using experimental protocols. From Gross-Pitaevskii simulations our study reveals a complex, multistage evolution; this includes a chaotic intermediate "heating" stage followed by a spontaneous reentrance to the BEC. The observed behavior is reminiscent of evolution in cosmological models.

cond-mat.quant-gas↗

arXiv2021

Dynamics of domain walls in a Bose-Einstein condensate driven by density-dependent gauge field

Dynamical coupling between matter and gauge fields underlies the emergence of many exotic particle-like excitations in condensed matter and high energy physics. An important stepping stone to simulate this physics in atomic quantum gases relies on the synthesis of density-dependent gauge fields. Here we demonstrate deterministic formation of domain walls in a stable Bose-Einstein condensate with a synthetic gauge field that depends on the atomic density. The gauge field is created by simultaneous modulations of the optical lattice potential and interatomic interactions, and results in domains of atoms condensed into two different momenta. Modeling the domain walls as elementary excitations, we find that the domain walls respond to synthetic electric field with a charge-to-mass ratio larger than and opposite to that of the bare atoms. Our work offers promising prospects to simulate the dynamics and interactions of novel excitations in quantum systems with dynamical gauge fields.

cond-mat.quant-gas↗

arXiv2020

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

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 demonstrating the strong link between jet emission and the underlying quantum system, bears on the recent emphasis on jet sub-structure in particle physics.

cond-mat.quant-gas↗

arXiv2019

Pattern formation in a driven Bose-Einstein Condensate

Pattern formation is ubiquitous in nature from morphogenesis and cloud formation to galaxy filamentation. More often than not, patterns arise in a medium driven far from equilibrium due to the interplay of dynamical instability and nonlinear wave mixing. We report, based on momentum and real space pattern recognition, formation of density patterns with two- (D$_2$), four- (D$_4$) and six-fold (D$_6$) symmetries in Bose-Einstein condensates (BECs) with atomic interactions driven at two frequencies. The symmetry of the pattern is controlled by the ratio of the frequencies. The D$_6$ density waves, in particular, arise from a resonant wave mixing process that coherently correlates and enhances the excitations that respect the symmetry.

cond-mat.quant-gas↗

arXiv2018

Super-resolution microscopy of cold atoms in an optical lattice

Super-resolution microscopy has revolutionized the fields of chemistry and biology by resolving features at the molecular level. Such techniques can be either "stochastic," gaining resolution through precise localization of point source emitters, or "deterministic," leveraging the nonlinear optical response of a sample to improve resolution. In atomic physics, deterministic methods can be applied to reveal the atomic wavefunction and to perform quantum control. Here we demonstrate super-resolution imaging based on nonlinear response of atoms to an optical pumping pulse. With this technique the atomic density distribution can be resolved with a point spread function FWHM of 32(4) nm and a localization precision below 1 nm. The short optical pumping pulse of 1.4 $μ$s enables us to resolve fast atomic dynamics within a single lattice site. A byproduct of our scheme is the emergence of moiré patterns on the atomic cloud, which we show to be immensely magnified images of the atomic density in the lattice. Our work represents a general approach to accessing the physics of cold atoms at the nanometer scale, and can be extended to higher dimensional lattices and bulk systems for a variety of atomic and molecular species.

cond-mat.quant-gas↗