We study the quantum to classical transition in bipartite entangled systems in which one system is continuously coupled to a measurement apparatus as in the von Neumann model of quantum measurement. As an example, we study the open system dynamics of a particle in a harmonic well whose motion in the well is coupled to the internal spin. This system provides a rich illustration of the quantum to classical transition in weakly measured coupled systems. We analyze and derive conditions for which the dual constraints of strong localization/small noise required for the quantum-classical transition are satisfied for both regular and chaotic dynamics. We also study the dynamics of bipartite entanglement in the regime where classical trajectories emerge in the measurement record. Our analysis shows the surprising result that bipartite entanglement can persist in the classical limit.We study the quantum to classical transition in bipartite entangled systems in which one system is continuously coupled to a measurement apparatus as in the von Neumann model of quantum measurement. As an example, we study the open system dynamics of a particle in a harmonic well whose motion in the well is coupled to the internal spin. This system provides a rich illustration of the quantum to classical transition in weakly measured coupled systems. We analyze and derive conditions for which the dual constraints of strong localization/small noise required for the quantum-classical transition are satisfied for both regular and chaotic dynamics. We also study the dynamics of bipartite entanglement in the regime where classical trajectories emerge in the measurement record. Our analysis shows the surprising result that bipartite entanglement can persist in the classical limit.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEMay 23, 20050 citations

Computable constraints on entanglement-sharing of multipartite quantum states

Yong-Cheng Ou, Mark Byrd

\Negativity is regarded as an important measure of entanglement in quantum information theory. In contrast to other measures of entanglement, it is easily computable for bipartite states in arbitrary dimensions. In this paper, based on the negativity and realignment, we provide a set of entanglement-sharing constraints for multipartite states, where the entanglement is not necessarily limited to bipartite and pure states, thus aiding in the quantification of constraints for entanglement-sharing. These may find applications in studying many-body systems.\Negativity is regarded as an important measure of entanglement in quantum information theory. In contrast to other measures of entanglement, it is easily computable for bipartite states in arbitrary dimensions. In this paper, based on the negativity and realignment, we provide a set of entanglement-sharing constraints for multipartite states, where the entanglement is not necessarily limited to bipartite and pure states, thus aiding in the quantification of constraints for entanglement-sharing. These may find applications in studying many-body systems.

arXiv:1004.5148Quantum Information and ComputationMar 1, 20102 citations

Two-parameter bipartite entanglement measure

Chen-Ming Bai, Yu Luo

Entanglement concurrence is an important bipartite entanglement measure that has found wide applications in quantum technologies. In this work, inspired by unified entropy, we introduce a two-parameter family of entanglement measures, referred to as the unified $(q,s)$ -concurrence. Both the standard entanglement concurrence and the recently proposed $q$ -concurrence emerge as special cases within this family. By combining the positive partial transposition and realignment criteria, we derive an analytical lower bound for this measure for arbitrary bipartite mixed states, revealing a connection to strong separability criteria. Explicit expressions are obtained for the unified $(q,s)$ -concurrence in the cases of isotropic and Werner states under the constraint $q>1$ and $qs\geq 1$ . Furthermore, we explore the monogamy properties of the unified $(q,s)$ -concurrence for $q\geq 2$ , $0\leq s\leq 1$ and $1\leq qs\leq 3$ , in qubit systems. In addition, we derive an entanglement polygon inequality for the unified $(q,s)$ -concurrence with $q\geq 1$ and $qs\geq 1$ , which manifests the relationship among all the marginal entanglements in any multipartite qudit system.Entanglement concurrence is an important bipartite entanglement measure that has found wide applications in quantum technologies. In this work, inspired by unified entropy, we introduce a two-parameter family of entanglement measures, referred to as the unified $(q,s)$-concurrence. Both the standard entanglement concurrence and the recently proposed $q$-concurrence emerge as special cases within this family. By combining the positive partial transposition and realignment criteria, we derive an analytical lower bound for this measure for arbitrary bipartite mixed states, revealing a connection to strong separability criteria. Explicit expressions are obtained for the unified $(q,s)$-concurrence in the cases of isotropic and Werner states under the constraint $q>1$ and $qs\geq 1$. Furthermore, we explore the monogamy properties of the unified $(q,s)$-concurrence for $q\geq 2$, $0\leq s\leq 1$ and $1\leq qs\leq 3$, in qubit systems. In addition, we derive an entanglement polygon inequality for the unified $(q,s)$-concurrence with $q\geq 1$ and $qs\geq 1$, which manifests the relationship among all the marginal entanglements in any multipartite qudit system.

quant-pharXiv:2601.22568Feb 2, 20260 citations

Multiply constrained bounds on measures of entanglement

Anil Shaji

Bulletin of the American Physical SocietyMar 5, 20070 citations

Entanglement measures for multipartite quantum systems: limitations and new approaches

Reza Hamzehofi

arXiv:2408.10272The European Physical Journal DMay 1, 20261 citation

(q,s)

-concurrence. Both the standard entanglement concurrence and the recently proposed

q

-concurrence emerge as special cases within this family. By combining the positive partial transposition and realignment criteria, we derive an analytical lower bound for this measure for arbitrary bipartite mixed states, revealing a connection to strong separability criteria. Explicit expressions are obtained for the unified

(q,s)

-concurrence in the cases of isotropic and Werner states under the constraint

q>1

and

qs\geq 1

. Furthermore, we explore the monogamy properties of the unified

(q,s)

-concurrence for

q\geq 2

0\leq s\leq 1

and

1\leq qs\leq 3

, in qubit systems. In addition, we derive an entanglement polygon inequality for the unified

(q,s)

-concurrence with

q\geq 1

and

qs\geq 1

, which manifests the relationship among all the marginal entanglements in any multipartite qudit system.