arXiv subjects

Yingmei Liu

Publications and source records attributed to Yingmei Liu.

9 recordsLinked to original sources

arXiv2026

Graduate Training in Quantum Information Science and Engineering: Lessons, Challenges, and a Roadmap from the NSF Research Traineeship Programs

Since 2019, eighteen NSF Research Traineeship (NRT) awards in quantum information science and engineering (QISE) and adjacent fields have been funded, constituting the largest NSF-coordinated investment in graduate QISE training in the United States. Synthesizing lessons from our programs, we work through the central tensions that every QISE graduate program must negotiate: between depth in a home discipline and breadth across the field, between structured instruction and open-ended experiential and hands-on learning, and between training individual specialists and cultivating teams that collectively cover all areas of QISE. We describe the structural and pedagogical innovations the NRT programs have developed in response, assess what is working and what remains unresolved, and sketch 12 open problems the community will need to address as QISE graduate education scales beyond the well-resourced research universities where it has up till now been mainly concentrated. Eight concrete recommendations follow: (1) adopt the startup model of team-based training as an organizing philosophy; (2) invest immediately in sensing and communication curriculum development; (3) build student agency into program governance, not just activities; (4) establish structural mechanisms for industrial engagement rather than depending on goodwill; (5) design for sustainability from year one; (6) develop graduate-level textbooks spanning all three QISE pillars: computing, sensing, and communications; (7) establish shared outcome assessment instruments across programs; and (8) develop structured mechanisms for faculty professional development in QISE.

physics.ed-ph↗

arXiv2023

Engineering Dynamical Phase Diagrams with Driven Lattices in Spinor Gases

We experimentally demonstrate that well-designed driven lattices are versatile tools to simultaneously tune multiple key parameters (namely spin-dependent interactions, spinor phase, and Zeeman energy) for manipulating phase diagrams of spinor gases with negligible heating and atom losses. This opens a new avenue for studying dynamical phase transitions in engineered Hamiltonians. The driven lattice creates additional separatrices in phase space at driving-frequency-determined locations, with progressively narrower separatrices at higher Zeeman energies due to modulation-induced higher harmonics. The vastly expanded range of magnetic fields at which significant spin dynamics occur and improved sensitivities at higher harmonics represent a step towards quantum sensing with ultracold gases.

cond-mat.quant-gas↗

arXiv2023

Manipulation of nonequilibrium spin dynamics of an ultracold gas in a moving optical lattice

The isolation and control of disparate degrees of freedom underpin quantum simulators. We advance the programmability of cold atom quantum simulators with a first realization of the dynamic interplay of spatial and spin degrees of freedom. We experimentally demonstrate that violent spatial evolutions tune long-lived coherent spin dynamics and develop a model of quantum spin-mixing incorporating the spatial evolution via time-dependent spin-spin interactions. Our results open new paths towards the simulation of quantum spin models with tunable interactions via tailored spatial dynamics.

cond-mat.quant-gas↗

arXiv2022

Detecting Topological phase transitions in a double kicked quantum rotor

We present a concrete theoretical proposal for detecting topological phase transitions in double kicked atom-optics kicked rotors with internal spin-1/2 degree of freedom. The implementation utilizes a kicked Bose-Einstein condensate evolving in one-dimensional momentum space. To reduce influence of atom loss and phase decoherence we aim to keep experimental durations short while maintaining a resonant experimental protocol. Experimental limitations induced by phase noise, quasimomentum distributions, symmetries, and the AC-Stark shift are considered. Our results thus suggest a feasible and optimized procedure for observing topological phase transitions in quantum kicked rotors.

cond-mat.quant-gas↗

arXiv2022

Light-shift induced behaviors observed in momentum-space quantum walks

Over the last decade there have been many advances in studies of quantum walks (QWs) including a momentum-space QW recently realized in our spinor Bose-Einstein condensate system. This QW possessed behaviors that generally agreed with theoretical predictions; however, it also showed momentum distributions that were not adequately explained by the theory. We present a theoretical model which proves that the coherent dynamics of the spinor condensate is sufficient to explain the experimental data without invoking the presence of a thermal cloud of atoms as in the original theory. Our numerical findings are supported by an analytical prediction for the momentum distributions in the limit of zero-temperature condensates. This current model provides more complete explanations to the momentum-space QWs that can be applied to study quantum search algorithms and topological phases in Floquet-driven systems.

quant-ph↗

arXiv2009

Number Fluctuations and Energy Dissipation in Sodium Spinor Condensates

We characterize fluctuations in atom number and spin populations in F=1 sodium spinor condensates. We find that the fluctuations enable a quantitative measure of energy dissipation in the condensate. The time evolution of the population fluctuations shows a maximum. We interpret this as evidence of a dissipation-driven separatrix crossing in phase space. For a given initial state, the critical time to the separatrix crossing is found to depend exponentially on the magnetic field and linearly on condensate density. This crossing is confirmed by tracking the energy of the spinor condensate as well as by Faraday rotation spectroscopy. We also introduce a phenomenological model that describes the observed dissipation with a single coefficient.

cond-mat.other↗

arXiv2009

Quantum Phase Transitions and Continuous Observation of Spinor Dynamics in an Antiferromagnetic Condensate

Condensates of spin-1 sodium display rich spin dynamics due to the antiferromagnetic nature of the interactions in this system. We use Faraday rotation spectroscopy to make a continuous and minimally destructive measurement of the dynamics over multiple spin oscillations on a single evolving condensate. This method provides a sharp signature to locate a magnetically tuned separatrix in phase space which depends on the net magnetization. We also observe a phase transition from a two- to a three-component condensate at a low but finite temperature using a Stern-Gerlach imaging technique. This transition should be preserved as a zero-temperature quantum phase transition.

cond-mat.other↗

arXiv2005

Temperature dependence of exciton Auger decay process in Cuprous Oxide

We report theoretical and experimental study on Auger decay of excitons in Cuprous Oxide in a wide range of temperatures, from 2 Kelvin to 325 Kelvin, in single-photon surface excitation. We find that the Auger constant linearly increases with temperature above 100 Kelvin. This constant is important for experiments on Bose condensation of excitons.

cond-mat.other↗

arXiv2004

Resonant two-photon excitation of 1s paraexcitons in Cuprous Oxide

We have created paraexcitons in Cuprous Oxide via resonant two-photon generation, and examined their population dynamics by means of time-correlated single photon detection. Confining the excitons to a constant volume in a harmonic potential trap made with inhomogeneous applied stress along the [001] axis, we find that paraexcitons are created directly, and orthoexcitons appear primarily through the well-known excitonic Auger process. Hot excitons are also created via a three-photon process when the IR laser is non-resonant. Also we generate excitons with two colliding pulses, and the luminescence is weaker than that from one beam excitation with same total laser power. These results show that resonant one-beam two-photon generation of paraexcitons is a promising way to pursue Bose-Einstein condensation of paraexcitons.

cond-mat.other↗