物理学家首次制造出量子回旋镖

诸平

In the quantum boomerang effect, particles return to their starting positions, on average, after a nudge. A new experiment (shown) demonstrates a version of the effect using lithium atoms.

The Weld Lab's quantum boomerang showed a lithium atom's initial departure and return to average zero momentum despite periodic energy "kicks" from their quantum kicked rotor

https://www.newscientist.com/article/2323871-physicists-have-made-a-quantum-boomerang-for-the-first-time/

David Weld

据《新科学家》（New Scientist）杂志网站2022年6月11日报道，物理学家首次制造出量子回旋镖（Physicists have made a quantum boomerang for the first time）。数十万个冷却到接近绝对零的锂原子表现出一种奇怪的量子效应，有点像回旋镖（boomerang）。这是研究人员首次成功地证明了一种称为量子回旋镖效应（quantum boomerang effect）的奇怪现象。

美国加州大学圣巴巴拉分校（University of California, Santa Barbara）的大卫·韦尔德（David Weld）和他的同事在一个小型真空密封箱内冷却了数十万个接近绝对零的锂原子（ close to absolute zero）他们使用激光将锂原子排列成一条直线，并将它们保持在特定的量子态，他们希望这会揭示回旋镖效应。

然后研究人员使用激光轻推这些原子。这导致它们从平均动量为零变为平均动量为正。如果同样的变化发生在一个球上，它就会滚开，但由于量子回旋镖效应，研究小组发现原子的平均动量很快就回到了零。

理论家最初提出，这种回旋镖效应可能发生在电子在充满灰尘颗粒的晶体内移动时，但事实证明这很难证明和研究。大卫·韦尔德和团队通过专注于可以用激光精确操纵的非常冷的原子来回避这个困难。

大卫·韦尔德及其同事在5月份在美国佛罗里达州奥兰多（Orlando, Florida）举行的DAMOP 会议（ DAMOP conference）上介绍了这项新实验。详见

53rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics

Monday–Friday, May 30–June 3 2022; Orlando, Florida

Session X05: Dynamics of Cold Atoms in Optical Lattices

8:00 AM–10:00 AM, Friday, June 3, 2022
Room: Salon 9/10
Chair: Mateusz Borkowski, University of Amsterdam

Abstract: X05.00004 : Observation of the quantum boomerang effect*

8:36 AM–8:48 AM 

Presenter:

Jeremy Tanlimco (University of California, Santa Barbara)

Authors:

Jeremy Tanlimco (University of California, Santa Barbara)

Roshan Sajjad (University of California, Santa Barbara)

Hector Mas (University of California, Santa Barbara)

Alec Cao (Cavendish Laboratory, University of Cambridge)

Eber Nolasco-Martinez (University of California, Santa Barbara)

Ethan Q Simmons (University of California, Santa Barbara)

Flávio L. N Santos (Universidade Federal do Rio Grande do Norte)

Patrizia Vignolo (Université Côte d'Azur, CNRS, Institut de Physique de Nice,)

Tommaso Macrì (Universidade Federal do Rio Grande do Norte)

David M Weld (University of California, Santa Barbara)

A particle in an Anderson-localized system, if launched in any direction, should on average return to its starting point and stay there. Despite the central role played by Anderson localization in the modern understanding of condensed matter, this "quantum boomerang" effect, an essential feature of the localized state, was only recently theoretically predicted. We report the first experimental observation of the quantum boomerang effect. Using a degenerate Bose gas and a phase-shifted pair of optical lattices, we not only confirm the predicted dependence of the boomerang effect on Floquet gauge, but also elucidate the crucial role of initial state symmetries.  Highlighting the key role of localization, we observe that as stochastic kicking destroys dynamical localization, the quantum boomerang effect also disappears. Measured dynamics are in agreement with numerical models and with predictions of an analytical theory we present, which clarifies the connection between time-reversal symmetry and boomerang dynamics. These results showcase a unique experimental probe of the underlying quantum nature of Anderson localized matter.

大卫·韦尔德说，他们研究的下一个目标是确定当超冷原子彼此非常强烈地相互作用时是否会发生回旋镖。这种非常协调的原子的行为还没有被很好地理解，所以看到它们回旋镖可能会发现一些关于量子物理学的新东西。

此研究得到了美国空军科学研究办公室(Air Force Office of Scientific Research: FA9550-20-1-0240)、陆军研究办公室(Army Research Office: W911NF-20-1-0294)、美国国家科学基金会(National Science Foundation: CAREER 1555313)、埃德乐曼量子创新中心（Eddleman Center for Quantum Innovation）、NSF QLCI项目(NSF QLCI program through grant number OMA-2016245)、CNPq(CNPq: grant no. 311079/2015-6)、Serrapilheira研究所(Serrapilheira Institute: grant number Serra-1812-27802)、UCSB NSF量子铸造通过Q-AMASEi计划(UCSB NSF Quantum Foundry through the Q-AMASEi program: Grant No. DMR-1906325)以及美国国家科学基金会研究生研究奖学金计划(NSF Graduate Research Fellowship Program: grant DGE2040434) 的支持。

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