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Annalen der Physik

Quadripartite entanglement from coupled type I second harmonic generation

Guo Juan, Shuqin Zhai, Zhai Ze‐hui

Published Aug 6, 2015• 1 citation
Publisher

Abstract

We present a feasible protocol of continuous variable quadripartite entanglement from the coupled type I second harmonic generation (SHG) below threshold. According to the sufficient inseparability criteria for multipartite continuous variable (CV) entanglement, the four output fields are proved to be multicolored entangled beams in separable locations with four‐mode amplitude quadratures correlation and relative phase quadratures correlation. It shows that the coupled system can produce a compact tunable multimode entangled source that can be applied into the quantum communication. image

DOI
10.1002/andp.201500182

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We present a feasible protocol of continuous variable quadripartite entanglement from the coupled type I second harmonic generation (SHG) below threshold. According to the sufficient inseparability criteria for multipartite continuous variable (CV) entanglement, the four output fields are proved to be multicolored entangled beams in separable locations with four‐mode amplitude quadratures correlation and relative phase quadratures correlation. It shows that the coupled system can produce a compact tunable multimode entangled source that can be applied into the quantum communication. image
A generation system of continuous-variable (CV) quadripartite entangled state based on two cascaded second-harmonic generation (SHG) cavities below the threshold is investigated. Two reflected fundamental beams of the first cavity, the reflected second-harmonic beam and the output fourth-harmonic beam of the second cavity are proved to be entangled, and the dependence of the entanglement degree on the normalized frequency, pump parameter, fourth-harmonic loss parameter, and second-harmonic loss parameter is also analyzed. Due to the fact that the cavity parameters and the nonlinear crystals of the two SHG cavities can be freely chosen, the practicality of the proposed protocol is relatively perfect and the system can also be extended to the preparation of multicolor entangled states for a quantum network.
An experimentally feasible intracavity coupler scheme is proposed to generate bright quadripartite continuous-variable (CV) entanglement by the coupled second-harmonic generation processes. By solving the steady-state equations and calculating the correlation spectra of the four output beams, we show that the four output beams are all entangled with each other according to the sufficient inseparability criterion for multipartite CV entanglement. By utilizing the upconversion process, the generated four entanglement fields have macroscopic intensities as soon as the input fields are turned on.
In this paper, tripartite entanglement among the two pump fields and the second-order harmonic field is established in the process of type-II second-order harmonic generation (SHG) with a triply resonant optical cavity below threshold. A sufficient inseparability criterion for continuous-variable tripartite entanglement proposed by van Loock and Furusawa is used to evaluate the degree of the quadrature--phase-amplitude correlations between the three modes. The dependence of the entanglement on the pump parameter and analysis frequency is also discussed. It is shown that the best entanglement appears at the appropriate pump power and analysis frequency. These three entangled states with different frequencies generated directly from a simple SHG process make the scheme useful for the application in quantum communication and network.
Abstract We propose an experimentally feasible scheme to produce bright six-partite continuous-variable (CV) entanglement by coupled intracavity non-degenerate parametric down-conversion operating above-threshold. The six-partite entanglement properties of the output fields are theoretically analyzed according to the sufficient inseparability criterion for multipartite CV entanglement. Such compact tunable multipartite CV entanglement, generated from a coupled system, could be used in quantum communications and networks.
Abstract We propose an experimentally feasible scheme to produce bright four-color continuous-variable entanglement by intracavity quasi-phase-matching cascaded nonlinear optical frequency conversion in only one optical superlattice. The second, third and fourth harmonics can be generated by frequency doubling of the input fundamental field at frequency , the sum frequency of fundamental and second harmonic fields, and frequency doubling of the second harmonic field, respectively. The entanglement properties influenced by system parameters are theoretically discussed according to the sufficient inseparability criterion proposed by van Loock and Furusawa. Such compact multipartite continuous-variable entanglement has potential applications in quantum communication and computation networks.