Wigner Centennial: His Function, and Its Environmental Decoherence

Wigner and his many friends: A new no-go result?

In April 2016, Daniela Frauchiger and Renato Renner published an article online in which they introduce a Gedankenexperiment that led them to conclude that single-world interpretation of quantum theory cannot be self-consistent. In a new version of the paper, published in September 2018, the authors moderate their original claim by concluding that quantum theory cannot be extrapolated to complex systems, at least not in a straightforward manner. The purpose of this article is to offer a careful reconstruction of the F-R argument, which allows us to show that: (i) the argument can be more clear…

Internal Space-time Symmetries according to Einstein, Wigner, Dirac, and Feynman

When Einstein formulated his special relativity in 1905, he established the law of Lorentz transformations for point particles. It is now known that particles have internal space-time structures. Particles, such as photons and electrons, have spin variables. Protons and other hadrons are regarded as bound states of more fundamental particles called quarks which have their internal variables. It is still one of the most outstanding problems whether these internal space-time variables are transformed according to Einstein's law of Lorentz transformations. It is noted that Wigner, Dirac, and Feyn…

Some properties of Wigner $3j$ coefficients: non-trivial zeros and connections to hypergeometric functions

The contribution of Jacques Raynal to angular-momentum theory is highly valuable. In the present article, I intend to recall the main aspects of his work related to Wigner $3j$ symbols. It is well known that the latter can be expressed with a hypergeometric series. The polynomial zeros of the $3j$ coefficients were initially characterized by the number of terms of the series minus one, which is the degree of the coefficient. A detailed study of the zeros of the $3j$ coefficient with respect to the degree $n$ for $J = a + b + c \leq 240$ ($a$, $b$ and $c$ being the angular momenta in the first …

传播微波光子的计算机断层成像

Computed tomography of propagating microwave photons

本文提出利用超导测辐射热计结合双场干涉实现无放大的传播微波光子Wigner函数断层成像，并借鉴CT原理，通过压缩感知和神经网络将投影次数降至三次，为超导量子网络中的实时量子错误诊断与纠正提供新方法。

AQFT 中的测量方案、语境性与 Wigner 的朋友思想实验

Measurement Schemes in AQFT, Contextuality and the Wigner's Friend Gedankenexperiment

本文旨在连接 Hepp 的退相干测量描述与 Fewster–Verch 广义协变测量方案，并重新解释 Frauchinger-Renner 思想实验，进而分析测量设置的语境性。

Non-equilibrium Quantum Many-Body Green Function Formalism in the light of Quantum Information Theory

The following issues are discussed inspired by the recent paper of Kadanoff (arXiv: 1403:6162): (a) Construction of a generalized one-particle Wigner distribution (GWD) function (analog of the classical distribution function) from which the quantum kinetic equation due to Kadanoff and Baym (KB) is derived, often called the Quantum Boltzmann Equation (QBE); (b) The equation obeyed by this has a collision contribution in the form of a two-particle Green function. This term is manipulated to have Kinetic Entropy in parallel to its counterpart in the classical Boltzmann kinetic equation for the cl…

States that "look the same" with respect to every basis in a mutually unbiased set

A complete set of mutually unbiased bases in a Hilbert space of dimension $d$ defines a set of $d+1$ orthogonal measurements. Relative to such a set, we define a "MUB-balanced state" to be a pure state for which the list of probabilities of the $d$ outcomes of one of these measurements is independent of the choice of measurement, up to permutations. In this paper we explicitly construct a MUB-balanced state for each prime power dimension $d$ for which $d = 3$ (mod 4). These states have already been constructed by Appleby in unpublished notes, but our presentation here is different in that both…

Does consciousness really collapse the wave function? A possible objective biophysical resolution of the measurement problem

An analysis has been performed of the theories and postulates advanced by von Neumann, London and Bauer, and Wigner, concerning the role that consciousness might play in the collapse of the wave function, which has become known as the measurement problem. This reveals that an error may have been made by them in the area of biology and its interface with quantum mechanics, when they called for the reduction of any superposition states in the brain through the mind or consciousness. Many years later Wigner changed his mind to reflect a simpler and more realistic objective position, expanded upon…