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Journal of Optics

Continuous variable multipartite entanglement in cascaded nonlinearities

Goutam Misra, Ashok Kumar

Published May 17, 2022• 3 citations

Abstract

Abstract Multipartite entanglement is the crucial requirement for quantum information processing, quantum computation, quantum communication and quantum sensing. Therefore, the generation and characterization of such entanglement are primary goals in quantum technologies. Here we theoretically study the multipartite continuous-variable quadrature entanglement generated by three symmetric cascaded nonlinear optical systems. Such cascaded systems allow us to study the bipartite, tripartite and quadripartite entanglement. We use different continuous-variable entanglement criteria to characterize the entanglement. We observe that only a few bipartite combinations show the entanglement out of all possible combinations, while most tripartite combinations are entangled. Interestingly such a system depicts a full quadripartite entanglement. Moreover, we show that, unlike the quadrature sum-variance entanglement criterion, the negative partial transpose criterion can show the entanglement in most cases. The present comprehensive analysis of the generation and characterization of the continuous-variable entanglement with cascaded systems would pave the way to realizing a complex quantum network.

DOI: 10.1088/2040-8986/ac7057

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Quantum entanglement shared by different parties enhances their capabilities to communicate, which is the core content of continuous-variable quantum optics and quantum information science. Here, we study an experimentally feasible scheme for generating quantum entanglement of bipartite and tripartite cases based on phase-sensitive cascaded four-wave mixing processes in rubidium vapor. Quantum entanglement of bipartite and tripartite cases in our system, which can be manipulated by the phases and the intensity gains of the input beams, is predicted. We also find a sufficient optimal single-condition criterion to give a valid description for genuine tripartite quantum entanglement in our system. The sufficient optimal single-condition criterion is convenient and can be extended to genuine multipartite entanglement.

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Abstract Quadripartite continuous-variable (CV) entanglement with different optical frequencies can be generated by nondegenerate optical parametric amplification cascaded with a sum-frequency process in only one optical superlattice. Firstly, the idler beam is generated by a different frequency process between pump and signal beams. Then, the sum-frequency beam will be generated by a cascaded sum-frequency process between pump and idler beams in the same optical superlattice. The conversion dynamics of the cascaded nonlinear processes is investigated by using a quantum stochastic method. The quantum correlations among pump, signal, idler and sum-frequency beams are calculated by applying a sufficient inseparability criteria for quadripartite CV entanglement. The results show that quadripartite CV entangled beams can be produced by this single-pass cascaded nonlinear process in one optical superlattice.