Quantum Gases

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Showing new listings for Thursday, 21 November 2024

New submissions (showing 4 of 4 entries)

[1] arXiv:2411.13041 [pdf, html, other]

Title: Out-of-equilibrium quantum thermochemical engine with one-dimensional Bose gas

Vijit V. Nautiyal

Comments: 26 pages, 5 figures. arXiv admin note: text overlap with arXiv:2410.16771 by other authors

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

We theoretically explore the finite-time performance of a quantum thermochemical engine using a harmonically trapped 1D Bose gas in the quasicondensate regime as the working fluid. Operating on an Otto cycle, the engine's unitary work strokes involve quenches of interatomic interactions, treating the fluid as a closed many-body quantum system evolving dynamically from an initial thermal state. During thermalization strokes, the fluid is an open system in diffusive contact with a reservoir, enabling both heat and particle exchange. Using a c--field approach, we demonstrate that the engine operates via chemical work, driven by particle flow from the hot reservoir. The engine's performance is analyzed in two regimes: (i) the out-of-equilibrium regime, maximizing power at reduced efficiency, and (ii) the quasistatic limit, achieving maximum efficiency but zero power due to slow driving. Remarkably, chemical work enables maximum efficiency even in sudden quench regime, offering a favorable trade-off between power and efficiency. Finally, we connect this work to prior research, showing that a zero-temperature adiabatic cycle provides an upper bound for efficiency and work at finite temperatures.

[2] arXiv:2411.13086 [pdf, html, other]

Title: Measurement of $p$-wave contacts in an ultracold Fermi gas of $^6$Li atoms

Kenta Nagase, Soki Oshima, Hikaru Takahashi, Takashi Mukaiyama

Comments: 6 pages, 3 figures

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

Using radio-frequency (RF) spectroscopy, we measure the $p$-wave contacts in a Fermi gas of $^6$Li atoms near the $p$-wave Feshbach resonance. The RF spectrum exhibits clear asymptotic behavior, characterized by $\tilde{\omega}^{-1/2}$ and $\tilde{\omega}^{-3/2}$ dependencies. The magnetic-field dependence of the $p$-wave contacts agrees reasonably well with the virial expansion theory in a detuned magnetic field range, validating the theory near the Fermi temperature. The $p$-wave contacts measured in this study constitute a second dataset, complementing the data obtained from the $^{40}$K system and contributing valuable insights into $p$-wave interactions in ultracold Fermi gases.

[3] arXiv:2411.13088 [pdf, html, other]

Title: Strong interaction induced dimensional crossover in 1D quantum gas

Zhongchi Zhang, Zihan Zhao, Huaichuan Wang, Ken Deng, Yuqi Liu, Wenlan Chen, Jiazhong Hu

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

We generated a one-dimensional quantum gas confined in an elongated optical dipole trap instead of 2D optical lattices. The sample, comprising thousands of atoms, spans several hundred micrometers and allows for independent control of temperature and chemical potential using Feshbach resonance. This allows us to directly observe and investigate the spatial distribution and associated excitation of 1D quantum gas without any ensemble averaging. In this system, we observed that the dimension of 1D gas will be popped up into 3D due to strong interaction without changing any trapping confinement. During the dimensional crossover, we found that increasing the scattering length leads to the failure of 1D theories, including 1D mean field, Yang-Yang equation, and 1D hydrodynamics. Specifically, the modified Yang-Yang equation effectively describes this 1D system at temperatures beyond the 1D threshold, but it does not account for the effects of stronger interactions. Meanwhile, we observe two possible quantized plateaus of breathing-mode oscillation frequencies predicted by 1D and 3D hydrodynamics, corresponding to weak and strong interactions respectively. And there is also a universal crossover connecting two different regimes where both hydrodynamics fail.

[4] arXiv:2411.13165 [pdf, html, other]

Title: Quantum transport in strongly correlated Fermi gases

Tilman Enss

Comments: 8 pages, contribution to the Proceedings of the 2024 IHP symposium ''Open questions in the quantum many-body problem''

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

Transport in strongly correlated fermions cannot be understood by fermionic quasiparticles alone. We present a theoretical framework for quantum transport that incorporates strong local correlations of fermion pairs. These contact correlations add essential contributions to viscous, thermal and sound transport coefficients. The bulk viscosity, in particular, receives its dominant contribution from pair excitations. Moreover, it can be measured elegantly by observing the response to a time-dependent scattering length even when the fluid is not moving. Rapid changes of the scattering length drive the system far out of local equilibrium, and we show how it relaxes back to equilibrium following a hydrodynamic attractor before a Navier-Stokes description becomes valid.

Cross submissions (showing 4 of 4 entries)

[5] arXiv:2411.12794 (cross-list from quant-ph) [pdf, html, other]

Title: A Universal Protocol for Quantum-Enhanced Sensing via Information Scrambling

Bryce Kobrin, Thomas Schuster, Maxwell Block, Weijie Wu, Bradley Mitchell, Emily Davis, Norman Y. Yao

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

We introduce a novel protocol, which enables Heisenberg-limited quantum-enhanced sensing using the dynamics of any interacting many-body Hamiltonian. Our approach - dubbed butterfly metrology - utilizes a single application of forward and reverse time evolution to produce a coherent superposition of a "scrambled" and "unscrambled" quantum state. In this way, we create metrologically-useful long-range entanglement from generic local quantum interactions. The sensitivity of butterfly metrology is given by a sum of local out-of-time-order correlators (OTOCs) - the prototypical diagnostic of quantum information scrambling. Our approach broadens the landscape of platforms capable of performing quantum-enhanced metrology; as an example, we provide detailed blueprints and numerical studies demonstrating a route to scalable quantum-enhanced sensing in ensembles of solid-state spin defects.

[6] arXiv:2411.12816 (cross-list from nucl-th) [pdf, html, other]

Title: Intertwined Quantum Phase Transitions in Bose and Bose-Fermi Systems

A. Leviatan

Comments: 18 pages, 13 figures, talk at Symposium "Symmetries in Science XIX", July 30 - August 4, 2023, Bregenz, Austria

Subjects: Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph)

Pronounced structural changes within individual configurations (Type I QPT), superimposed on an abrupt crossing of these configurations (Type II QPT), define the notion of intertwined quantum phase transitions (QPTs). We discuss and present evidence for such a scenario in finite Bose and Bose-Fermi systems. The analysis is based on algebraic models with explicit configuration mixing, where the two types of QPTs describe shape-phase transitions in-between different dynamical symmetries and shape-coexistence with crossing.

[7] arXiv:2411.13161 (cross-list from quant-ph) [pdf, html, other]

Title: A universal framework for the quantum simulation of Yang-Mills theory

Jad C. Halimeh, Masanori Hanada, Shunji Matsuura, Franco Nori, Enrico Rinaldi, Andreas Schäfer

Comments: 42 pages, 6 figures, 1 table

Subjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas); High Energy Physics - Lattice (hep-lat)

We provide a universal framework for the quantum simulation of SU(N) Yang-Mills theories on fault-tolerant digital quantum computers adopting the orbifold lattice formulation. As warm-up examples, we also consider simple models, including scalar field theory and the Yang-Mills matrix model, to illustrate the universality of our formulation, which shows up in the fact that the truncated Hamiltonian can be expressed in the same simple form for any N, any dimension, and any lattice size, in stark contrast to the popular approach based on the Kogut-Susskind formulation. In all these cases, the truncated Hamiltonian can be programmed on a quantum computer using only standard tools well-established in the field of quantum computation. As a concrete application of this universal framework, we consider Hamiltonian time evolution by Suzuki-Trotter decomposition. This turns out to be a straightforward task due to the simplicity of the truncated Hamiltonian. We also provide a simple circuit structure that contains only CNOT and one-qubit gates, independent of the details of the theory investigated.

[8] arXiv:2411.13190 (cross-list from quant-ph) [pdf, html, other]

Title: Ab-initio approach to Many-Body Quantum Spin Dynamics

Aditya Dubey, Zeki Zeybek, Fabian Köhler, Rick Mukherjee, Peter Schmelcher

Comments: 12 pages, 9 figures

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

A fundamental longstanding problem in studying spin models is the efficient and accurate numerical simulation of the long-time behavior of larger systems. The exponential growth of the Hilbert space and the entanglement accumulation at long times pose major challenges for current methods. To address these issues, we employ the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) framework to simulate the many-body spin dynamics of the Heisenberg model in various settings, including the Ising and XYZ limits with different interaction ranges and random couplings. Benchmarks with analytical and exact numerical approaches show that ML-MCTDH accurately captures the time evolution of one- and two-body observables in both one- and two-dimensional lattices. A comparison of ML-MCTDH with the discrete truncated Wigner approximation (DTWA) demonstrates that our approach excels in handling anisotropic models and consistently provides better results for two-point observables in all simulation instances. Our results indicate that the multilayer structure of ML-MCTDH is a promising numerical framework for handling the dynamics of generic many-body spin systems.

Replacement submissions (showing 3 of 3 entries)

[9] arXiv:2405.21065 (replaced) [pdf, html, other]

Title: Single-beam grating-chip 3D and 1D optical lattices

Alan Bregazzi, James P. McGilligan, Paul F. Griffin, Erling Riis, Aidan S. Arnold

Comments: 7 pages, 3 figures, Supplementary Material, to appear in Phys. Rev. Lett

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

Ultracold atoms are crucial for unlocking truly precise and accurate quantum metrology, and provide an essential platform for quantum computing, communication and memories. One of the largest ongoing challenges is the miniaturization of these quantum devices. Here, we show that the typically macroscopic optical lattice architecture at the heart of many ultra-precise quantum technologies can be realized with a single input laser beam on the same diffractive chip already used to create the ultracold atoms. Moreover, this inherently ultra-stable platform enables access to a plethora of new lattice dimensionalities and geometries, ideally suited for the design of high-accuracy, portable quantum devices.

[10] arXiv:2208.11525 (replaced) [pdf, other]

Title: Studying radiation of a white dwarf star falling on a black hole

Marek Nikołajuk (1), Tomasz Karpiuk (1), Lorenzo Ducci (2,3), Mirosław Brewczyk (1) ((1) Faculty of Physics, University of Białystok, Bialystok, Poland, (2) Department of Astronomy, University of Geneva, Versoix, Switzerland, (3) Institut fuer Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Eberhard Karls Universitat, Tuebingen, Germany)

Comments: 12 pages, 4 figures. New scaling included

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Quantum Gases (cond-mat.quant-gas); General Relativity and Quantum Cosmology (gr-qc)

We investigate electromagnetic and gravitational radiation generated during a process of the tidal stripping of a white dwarf star circulating a black hole. We model a white dwarf star by a Bose-Fermi droplet and use the quantum hydrodynamic equations to simulate evolution of a black hole-white dwarf binary system. While going through the periastron, the white dwarf loses a small fraction of its mass. The mass falling onto a black hole is a source of powerful electromagnetic and gravitational radiation. Bursts of ultraluminous radiation are flared at each periastron passage. This resembles the recurrent flaring of X-ray sources discovered recently by Irwin {\it et al.}. Gravitational energy bursts occur mainly through emission at very low frequencies. The accretion disc, formed due to stripping of a white dwarf, starts at some point to contribute continuously to radiation of both electromagnetic and gravitational types.

[11] arXiv:2402.19123 (replaced) [pdf, html, other]

Title: Sensing atomic superfluid rotation beyond the standard quantum limit

Rahul Gupta, Pardeep Kumar, Rina Kanamoto, M. Bhattacharya, Himadri Shekhar Dhar

Comments: 16 pages, 13 figures

Journal-ref: Phys. Rev. A 110, 053514 (2024)

Subjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Optics (physics.optics)

Atomic superfluids formed using Bose-Einstein condensates (BECs) in a ring trap are currently being investigated in the context of superfluid hydrodynamics, quantum sensing and matter-wave interferometry. The characterization of the rotational properties of such superfluids is important, but can presently only be performed by using optical absorption imaging, which completely destroys the condensate. Recent studies have proposed coupling the ring BEC to optical cavity modes carrying orbital angular momentum to make minimally destructive measurements of the condensate rotation. The sensitivity of these proposals, however, is bounded below by the standard quantum limit set by the combination of laser shot noise and radiation pressure noise. In this work, we provide a theoretical framework that exploits the fact that the interaction between the scattered modes of the condensate and the light reduces to effective optomechanical equations of motion. We present a detailed theoretical analysis to demonstrate that the use of squeezed light and backaction evasion techniques allows the angular momentum of the condensate to be sensed with noise well below the standard quantum limit. Our proposal is relevant to atomtronics, quantum sensing and quantum information.