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Luo C, Zhang H, Koh VPW, Wilson JD, Chu A, Holland MJ, Rey AM, Thompson JK. Momentum-exchange interactions in a Bragg atom interferometer suppress Doppler dephasing. Science 2024; 384:551-556. [PMID: 38696562 DOI: 10.1126/science.adi1393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 03/21/2024] [Indexed: 05/04/2024]
Abstract
Large ensembles of laser-cooled atoms interacting through infinite-range photon-mediated interactions are powerful platforms for quantum simulation and sensing. Here we realize momentum-exchange interactions in which pairs of atoms exchange their momentum states by collective emission and absorption of photons from a common cavity mode, a process equivalent to a spin-exchange or XX collective Heisenberg interaction. The momentum-exchange interaction leads to an observed all-to-all Ising-like interaction in a matter-wave interferometer. A many-body energy gap also emerges, effectively binding interferometer matter-wave packets together to suppress Doppler dephasing in analogy to Mössbauer spectroscopy. The tunable momentum-exchange interaction expands the capabilities of quantum interaction-enhanced matter-wave interferometry and may enable the realization of exotic behaviors, including simulations of superconductors and dynamical gauge fields.
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Affiliation(s)
- Chengyi Luo
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
| | - Haoqing Zhang
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
| | - Vanessa P W Koh
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
| | - John D Wilson
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
| | - Anjun Chu
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
| | - Murray J Holland
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
| | - Ana Maria Rey
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
| | - James K Thompson
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
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Young DJ, Chu A, Song EY, Barberena D, Wellnitz D, Niu Z, Schäfer VM, Lewis-Swan RJ, Rey AM, Thompson JK. Observing dynamical phases of BCS superconductors in a cavity QED simulator. Nature 2024; 625:679-684. [PMID: 38267683 DOI: 10.1038/s41586-023-06911-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 11/29/2023] [Indexed: 01/26/2024]
Abstract
In conventional Bardeen-Cooper-Schrieffer superconductors1, electrons with opposite momenta bind into Cooper pairs due to an attractive interaction mediated by phonons in the material. Although superconductivity naturally emerges at thermal equilibrium, it can also emerge out of equilibrium when the system parameters are abruptly changed2-8. The resulting out-of-equilibrium phases are predicted to occur in real materials and ultracold fermionic atoms, but not all have yet been directly observed. Here we realize an alternative way to generate the proposed dynamical phases using cavity quantum electrodynamics (QED). Our system encodes the presence or absence of a Cooper pair in a long-lived electronic transition in 88Sr atoms coupled to an optical cavity and represents interactions between electrons as photon-mediated interactions through the cavity9,10. To fully explore the phase diagram, we manipulate the ratio between the single-particle dispersion and the interactions after a quench and perform real-time tracking of the subsequent dynamics of the superconducting order parameter using nondestructive measurements. We observe regimes in which the order parameter decays to zero (phase I)3,4, assumes a non-equilibrium steady-state value (phase II)2,3 or exhibits persistent oscillations (phase III)2,3. This opens up exciting prospects for quantum simulation, including the potential to engineer unconventional superconductors and to probe beyond mean-field effects like the spectral form factor11,12, and for increasing the coherence time for quantum sensing.
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Affiliation(s)
- Dylan J Young
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
| | - Anjun Chu
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
- Center for Theory of Quantum Matter, University of Colorado, Boulder, CO, USA
| | - Eric Yilun Song
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
| | - Diego Barberena
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
- Center for Theory of Quantum Matter, University of Colorado, Boulder, CO, USA
| | - David Wellnitz
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
- Center for Theory of Quantum Matter, University of Colorado, Boulder, CO, USA
| | - Zhijing Niu
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
| | - Vera M Schäfer
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA
- Max-Planck-Institut für Kernphysik, Heidelberg, Germany
| | - Robert J Lewis-Swan
- Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK, USA
- Center for Quantum Research and Technology, University of Oklahoma, Norman, OK, USA
| | - Ana Maria Rey
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA.
- Center for Theory of Quantum Matter, University of Colorado, Boulder, CO, USA.
| | - James K Thompson
- JILA, NIST, and Department of Physics, University of Colorado, Boulder, CO, USA.
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Sarkar A, Sen S, Kumar S. Spectral crossovers in non-Hermitian spin chains: Comparison with random matrix theory. Phys Rev E 2023; 108:054210. [PMID: 38115444 DOI: 10.1103/physreve.108.054210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 10/10/2023] [Indexed: 12/21/2023]
Abstract
We present a systematic investigation of the short-range spectral fluctuation properties of three non-Hermitian spin-chain Hamiltonians using complex spacing ratios (CSRs). Specifically, we focus on the non-Hermitian variants of the standard one-dimensional anisotropic XY model having intrinsic rotation-time (RT) symmetry that has been explored analytically by Zhang and Song [Phys. Rev. A 87, 012114 (2013)1050-294710.1103/PhysRevA.87.012114]. The corresponding Hermitian counterpart is also exactly solvable and has been widely employed as a toy model in several condensed matter physics problems. We show that the presence of a random field along the x direction together with the one along the z direction facilitates integrability and RT-symmetry breaking, leading to the emergence of quantum chaotic behavior. This is evidenced by a spectral crossover closely resembling the transition from Poissonian to Ginibre unitary ensemble (GinUE) statistics of random matrix theory. Additionally, we consider two phenomenological random matrix models in this paper to examine 1D Poisson to GinUE and 2D Poisson to GinUE crossovers and the associated signatures in CSRs. Here 1D and 2D Poisson correspond to real and complex uncorrelated levels, respectively. These crossovers reasonably capture spectral fluctuations observed in the spin-chain systems within a certain range of parameters.
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Affiliation(s)
- Ayana Sarkar
- Department of Physics, Shiv Nadar Institution of Eminence, Gautam Buddha Nagar, Uttar Pradesh-201314, India
| | - Sunidhi Sen
- Department of Physics, Shiv Nadar Institution of Eminence, Gautam Buddha Nagar, Uttar Pradesh-201314, India
| | - Santosh Kumar
- Department of Physics, Shiv Nadar Institution of Eminence, Gautam Buddha Nagar, Uttar Pradesh-201314, India
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