Continuous-Discrete Entanglement

Paul Cummins

Xiao‐Feng Qian, Curtis J. Broadbent, Joseph H. Eberly

We report a summary of our recent work proposing a new Bell test for discrete-continuous entangled systems when the continuous variable state is unknown (i.e., arbitrary and inaccessible to direct measurements).

Fuli Li, Muhammad Suhail Zubairy

Manuel Gessner, Luca Pezzè, Augusto Smerzi

We develop a method to construct entanglement criteria for arbitrary multipartite systems of discrete or continuous variables and hybrid combinations of both. While any set of local operators generates a sufficient condition for entanglement of arbitrary quantum states, a suitable set leads to a necessary and sufficient criterion for pure states. The criteria are readily implementable with existing technology and reveal entanglement that remains undetected by the respective state-of-the-art methods for discrete and continuous variables.

Shou‐Bang Yang, Wen Ning, Ri‐Hua Zheng +2 more

The study of entanglement between discrete and continuous variables is an important theoretical and experimental topic in quantum information processing, for which entanglement swapping is one of the interesting elements. Entanglement swapping allows two particles without interacting with each other in any way, to form an entangled state by the action of another pair of entangled particles. In this paper, we propose an experimentally feasible scheme to realize deterministic entanglement swapping in the hybrid system with discrete and continuous variables. The process is achieved by preparing two pairs of entangled states, each is formed by a qubit and two quasi-orthogonal coherent state elements of a cavity, performing a Bell-state analysis through nonlocal operations on the continuous variable states of the two cavities, and projecting the two qubits into a maximally entangled state. The present scheme may be applied to other physical systems sustaining such hybrid discrete and continuous forms, providing a typical paradigm for entanglement manipulation through deterministic swapping operations.