Mode entanglement in nonlinear quantum-optical parametric processes

A. S. Chirkin, M. Yu. Saygin

We consider the forming of a four-mode entangled state for continuous variables (CV) in coupled optical parametric processes. The processes comprise one down-conversion process and two up-conversion ones. Such interactions can simultaneously be realized in a single aperiodical nonlinear photonic crystal. To reveal the entanglement between continuous variables at generated frequencies, the different criteria of the separability have been applied. We also consider teleportation of two-mode entangled CV state using the created four-mode state. It is shown that in the proposed scheme the fidelity of entangled CV teleportation can be almost perfect.

A. V. Nikandrov, A. S. Chirkin

Jing Zhang, Xiaoyu Liu, Rongguo Yang +1 more

Multipartite entanglement is a key resource for quantum information processing and quantum communication. We show that the robust entanglement among four filtered output optical modes can be achieved when there is a nonlinear crystal inside an optomechanical cavity. The optical parametric amplifier (OPA) gives rise to single-mode squeezing of the cavity modes; therefore, the entanglement among four output optical modes can be enhanced remarkably. Furthermore, the degree of quadripartite entanglement is influenced by the nonlinear gain of OPA and bandwidth of the filters. Large entanglement can be obtained by optimizing the filter functions, which is important for utilizing entangled light beams more efficiently in real experiments. This kind of multipartite entanglement will be useful and valuable in the area of quantum communication networks.

P. Tombesi

Feng Wen, Sijia Hui, Shaowei Zhang +7 more

Abstract In this study, a tunable continuous‐variable (CV) triple‐mode entanglement scheme generated by cascading a spontaneous parametric four‐wave and a sum‐frequency four‐wave mixing process is proposed. The entanglement feature of the triple‐mode is demonstrated by using a sufficient inseparability criterion. It is confirmed that the triple‐mode CV entanglement property, including the degree of violation of the sufficient inseparability criterion and the entanglement range in the frequency domain, can be modulated dynamically by modifying the nonlinear susceptibility and optical parameters. In particular, the intensity of the pumping field affects the modulation of the degree of entanglement, and the splitting of the entanglement spectrum comes from electromagnetically induced transparency. Although changing the relative detuning between the Stokes and anti‐Stokes fields can increase the entanglement degree of the triple‐mode, it results in the expansion of the entanglement range in frequency as well. Furthermore, although nonlinear susceptibility directly improves the degree of triple‐mode CV entanglement, optical detuning related nonlinear dispersion has an indirect effect as well. Such an optical triple‐mode CV entanglement with tunable properties can find applications in all‐optical quantum communication and pave the way for the generation and manipulation of multichannel quantum networks.

Geunhee Gwak, Chan Roh, Young-Do Yoon +2 more