Proper and Improper Separability

Proper and improper density matrices and the consistency of the Deutsch model for Local Closed Timelike Curves

We discuss the concept of proper and improper density matrixes and we argue that this issue is of fundamental importance for the understanding of the quantum-mechanical CTC model proposed by Deutsch. We arrive at the conclusion that under a realistic interpretation, the distinction between proper and improper density operators is not a relativistically covariant notion and this fact leads to the conclusion that the D-CTC model is physically inconsistent.

Proper Versus Improper Mixtures: Towards a Quaternionic Quantum Mechanics

The density operators obtained by taking partial traces do not represent proper mixtures of the subsystems of a compound physical system, but improper mixtures, since the coefficients in the convex sums expressing them never bear the ignorance interpretation. As a consequence, assigning states to these subsystems is problematical in standard quantum mechanics (subentity problem). Basing on the proposal provided in the SR interpretation of quantum mechanics, where improper mixtures are considered as true nonpure states conceptually distinct from proper mixtures, we show here that proper and imp…

Indistinguishability and improper mixtures

All quantum mixtures are what d'Espagnat has termed "improper." His "proper" mixture cannot be created -- if welcher weg, or distinguishing, information exists, an improper mixture results, while in the absence of such information, the resulting "mixture" is a pure state. D'Espagnat has claimed that an interpretation of the improper mixture in terms of subensembles leads to logical inconsistency; this claim is shown to be incorrect, as d'Espagnat's argument fails to account for the indistinguishability of the pure-state subensembles.

A quantum logical and geometrical approach to the study of improper mixtures

We study improper mixtures from a quantum logical and geometrical point of view. Taking into account the fact that improper mixtures do not admit an ignorance interpretation and must be considered as states in their own right, we do not follow the standard approach which considers improper mixtures as measures over the algebra of projections. Instead of it, we use the convex set of states in order to construct a new lattice whose atoms are all physical states: pure states and improper mixtures. This is done in order to overcome one of the problems which appear in the standard quantum logical f…

正当混合态与不正当混合态作为量子态反推的不同先验信念

Proper and improper mixed states serve as different prior beliefs for quantum state retrodiction

研究混合态作为先验信念在量子态反推中的差异，提出框架并证明等价条件，展示操作后果。

恰当与不恰当量子PAC学习

Proper vs Improper Quantum PAC learning

本研究提出匹配量子赠券收集问题最新下界的算法，并设计量子填充赠券收集问题变体，首次实现恰当与不恰当量子学习的渐近分离，相关技术可推广至填充量子数据场景。