We propose a hybrid approach to the experimental assessment of the genuine quantum features of a general system consisting of microscopic and macroscopic parts. We infer entanglement by combining dichotomic measurements on a bidimensional system and phase-space inference through the Wigner distribution associated with the macroscopic component of the state. As a benchmark, we investigate the feasibility of our proposal in a bipartite-entangled state composed of a single-photon and a multiphoton field. Our analysis shows that, under ideal conditions, maximal violation of a Clauser-Horne-Shimony-Holt-based inequality is achievable regardless of the number of photons in the macroscopic part of the state. The difficulty in observing entanglement when losses and detection inefficiency are included can be overcome by using a hybrid entanglement witness that allows efficient correction for losses in the few-photon regime.
Witnessing non-stationary and non-Markovian environments with a quantum sensor
Weizmann Institute of Science（魏茨曼科学研究所）；Centro Atómico Bariloche, CONICET, CNEA（巴里洛切原子中心，阿根廷国家科学技术研究委员会，阿根廷核能委员会）；Instituto de Nanociencia y Nanotechnologia, CNEA, CONICET（纳米科学与技术研究所，阿根廷核能委员会，阿根廷国家科学技术研究委员会）；Instituto Balseiro, CNEA, Universidad Nacional de Cuyo（巴尔塞罗研究所，阿根廷核能委员会，门多萨国立大学）；Physikalisches Institut, Universität Stuttgart（斯图加特大学第三物理研究所）
In many experiments on microscopic quantum systems, it is implicitly assumed that when a macroscopic procedure or "instruction" is repeated many times -- perhaps in different contexts -- each application results in the same microscopic quantum operation. But in practice, the microscopic effect of a single macroscopic instruction can easily depend on its context. If undetected, this can lead to unexpected behavior and unreliable results. Here, we design and analyze several tests to detect context-dependence. They are based on invariants of matrix products, and while they can be as data intensiv…
Quantum Darwinism offers an explanation for the emergence of classical objective features -- those we are used to at macroscopic scales -- from quantum properties at the microscopic level. The interaction of a quantum system with its surroundings redundantly proliferates information to many parts of the environment, turning it accessible and objective to different observers. But given that one cannot probe the quantum system directly, only its environment, how to witness whether an unknown quantum property can be deemed objective or not? Here we propose a probabilistic framework to analyze thi…
研究孤立量子系统中热平衡的性质和接近方法。一个孤立的宏观量子系统在纯态或混合态下，如果所有宏观观测量都相当精确地假定为热力学的值，那么它就被认为处于热平衡。对于这样的系统（或状态），我们说它处于宏观热平衡（MATE）。比MATE更强的要求是，即使是微观的可观测量（即，指的是小的子系统）具有与从微正则系综或等价的正则系综获得的概率分布一致的概率分布。对于这样的系统，我们说它处于微观热平衡（MITE）。MITE和MATE之间的区别对于具有多体局域化（MBL）的系统特别相关，对于MBL，能量本征函数不能在MITE中，而它们中的大部分（但不是全部）必须在MATE中。然而，如果我们考虑能量本征函数的叠加（即，典型的波函数$ψ$），那么对于一般的宏观系统，包括那些具有MBL的系统，大多数$ψ$都在MATE和MITE中。我们在这里探索MATE和MITE的性质，并比较这两个概念，从而详细阐述[Goldstein et al.，Phys.Rev.Lett. 115：100402（2015）]。
Reductionism is a prevalent viewpoint in science according to which all physical phenomena can be understood from fundamental laws of physics. Anderson [Science, 177, 393 (1972)], Laughlin and Pines [PNAS, 97, 28 (2000)], and others have countered this viewpoint and argued in favour hierarchical structure of the universe and laws. In this paper we advance the latter perspective by showing that some of the complex flow properties derived using hydrodynamic equations (macroscopic laws) are very difficult, if not impossible, to describe in microscopic framework---kinetic theory. These properties …
This article is mostly based on a talk I gave at the March 2021 meeting (virtual) of the American Physical Society on the occasion of receiving the Dannie Heineman prize for Mathematical Physics from the American Institute of Physics and the American Physical Society. I am greatly indebted to many colleagues for the results leading to this award. To name them all would take up all the space allotted to this article. (I have had more than 200 collaborators so far), I will therefore mention just a few: Michael Aizenman, Bernard Derrida, Shelly Goldstein, Elliott Lieb, Oliver Penrose, Errico Pres…
