Abstract
A new scheme is presented to directly produce fundamental, second-, and third-harmonic three-color continuous-variable (CV) entangled beams by cascaded quasi-phase-matched third-harmonic generation (THG) in an optical cavity. THG can be achieved with high efficiency through a coupled sum-frequency process between the second-harmonic and the fundamental fields. It is demonstrated that the three beams (fundamental, second-, and third-harmonic fields) are entangled with each other according to the CV entanglement criterion. In this scheme, only one crystal and one pump field can generate three-color CV entangled beams separated by an octave in frequency through quasi-phase-matched cascaded nonlinear process, which may be very useful for the applications in quantum communication and computation networks.
Highlights
Quantum entanglement attracts many interests in recent years since it is the central resource in the applications such as quantum communication and computation
Two-color CV entanglement produced by nondegenerate optical parametric oscillator (OPO) was predicted [2], and experimentally demonstrated both below [3] and above [4] the oscillation threshold
It was predicated that three-color CV entanglement among pump, signal and idler beams can be obtained using an OPO operating above the threshold [5], which has been realized by the recent experiment [6]
Summary
Quantum entanglement attracts many interests in recent years since it is the central resource in the applications such as quantum communication and computation. It was predicted that the perfect entanglement could be produced between the fundamental and the second-harmonic fields by the second-order nonlinear interaction [9], which has been experimentally verified recently [10]. Other suggestions were proposed to generate two-color tripartite entanglement among the fundamental and the second-harmonic fields through the type-II SHG system operating below [11] and above [12] the threshold. Third-harmonic generation (THG) can be obtained with high efficiency through cascaded sum-frequency process between the second-harmonic and the fundamental fields [16]. Third-harmonic fields) through a coupled nonlinear process of quasi-phase-matched THG. The second-harmonic field with the frequency of ω1 is generated by the first sum-frequency process. K0, k1, and k2 are the wave vectors of the fundamental, second-, and third-harmonic fields, respectively
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