Quantum Measurements and Information Restrictions in Algebraic QM

在一般测量下利用纠缠和非正交性限制增强的量子态鉴别

Enhanced quantum state discrimination under general measurements with entanglement and nonorthogonality restrictions

本文研究了在资源受限条件下，通过非正测量实现量子态鉴别误差低于Helstrom界限的可能性，展示了无需初始纠缠即可实现有效非正测量的方法。

Information Systems Self-description and Quantum Measurement Problem

Information-Theoretical restrictions on the systems self-descriptions are applied to Quantum Measurements Theory. For the quantum object S measurement by information system O such restrictions are described by the restricted states formalism by Breuer. The analogous restrictions obtained in Algebraic QM from the analysis of Segal algebra U of O observables; O restricted states set is defined as U dual space. From Segal theorem for the associative subalgebra it's shown that such states describe the random pointer outcomes observed by O in the individual events.

Weak values in a classical theory with an epistemic restriction

Weak measurement of a quantum system followed by postselection based on a subsequent strong measurement gives rise to a quantity called the weak value: a complex number for which the interpretation has long been debated. We analyse the procedure of weak measurement and postselection, and the interpretation of the associated weak value, using a theory of classical mechanics supplemented by an epistemic restriction that is known to be operationally equivalent to a subtheory of quantum mechanics. Both the real and imaginary components of the weak value appear as phase space displacements in the p…

Almost quantum correlations violate the no-restriction hypothesis

To identify which principles characterize quantum correlations, it is essential to understand in which sense this set of correlations differs from that of almost quantum correlations. We solve this problem by invoking the so-called no-restriction hypothesis, an explicit and natural axiom in many reconstructions of quantum theory stating that the set of possible measurements is the dual of the set of states. We prove that, contrary to quantum correlations, no generalised probabilistic theory satisfying the no-restriction hypothesis is able to reproduce the set of almost quantum correlations. Th…

解码器受局域性限制的稠密编码：量子编码器与超量子编码器

Dense Coding with Locality Restriction for Decoder: Quantum Encoders vs. Super-Quantum Encoders

本文基于非对称性资源理论研究解码器受局域性限制的稠密编码，导出可达速率，并证明其在多种放宽测量乃至 GPT 超量子编码器下均不可提升。

Algebraic properties of quantum reference frames: Does time fluctuate?

Quantum reference frames are expected to differ from classical reference frames because they have to implement typical quantum features such as fluctuations and correlations. Here, we show that fluctuations and correlations of reference variables, in particular of time, are restricted by their very nature of being used for reference. Mathematically, this property is implemented by imposing constraints on the system to make sure that reference variables are not physical degrees of freedom. These constraints not only relate physical degrees of freedom to reference variables in order to describe …

Algebraic Theory of Measurement Processes in Quantum Systems

Here we deal in a pedagogical way with an approach to construct an algebraic structure for the Quantum Mechanical measurement processes from the concept of \emph{Measurement Symbol}. Such concept was conceived by Julian S. Schwinger and constitutes a fundamental piece in his variational formalism and its several applications.