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Physical Review A

Generation of broadband entangled light through cascading nondegenerate optical parametric amplifiers

Wen-ping He, Fuli Li

Published Jul 26, 2007• 17 citations
Publisher

Abstract

We consider a system consisting of $N$ nondegenerate optical parametric amplifiers (NOPAs) operating below threshold and linked with each other in a cascading way, each taking the output subharmonic fields from the previous one as the input fields. The entanglement properties of the subharmonic fields from these cascading nondegenerate optical parametric amplifiers (CNOPAs) are investigated. We find that, if the input subharmonic fields of the first NOPA in the cascading line are in the vacuum state, the output fields from the later NOPAs exhibit excellent broadband entanglement, and the entanglement frequency band is broadened notably with increased number of cascading NOPAs. We also discuss the application of the entangled light generated from the CNOPAs to broadband teleportation, and find that the maximum width of the fidelity spectrum of teleportation of broadband coherent states can be greatly broadened.

DOI
10.1103/physreva.76.012328

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We consider a system consisting of NNN nondegenerate optical parametric amplifiers (NOPAs) operating below threshold and linked with each other in a cascading way, each taking the output subharmonic fields from the previous one as the input fields. The entanglement properties of the subharmonic fields from these cascading nondegenerate optical parametric amplifiers (CNOPAs) are investigated. We find that, if the input subharmonic fields of the first NOPA in the cascading line are in the vacuum state, the output fields from the later NOPAs exhibit excellent broadband entanglement, and the entanglement frequency band is broadened notably with increased number of cascading NOPAs. We also discuss the application of the entangled light generated from the CNOPAs to broadband teleportation, and find that the maximum width of the fidelity spectrum of teleportation of broadband coherent states can be greatly broadened.
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We demonstrate the enhanced quantum noise reduction of the output field from an optical parametric amplifier (OPA) by employing the cascaded optical parametric amplifiers (COPA), in which the output field of one OPA is the input field of the subsequent one. The output field noise formulas of the cascaded degenerate and nondegenerate OPAs (CDOPA and CNOPA) are obtained. The analytical results show that a CDOPA and a CNOPA can generate squeezing beams and entangled beams with a wider bandwidth under a low pump parameter, respectively. The cavity output efficiency and the intracavity loss are the main factors for improving the degrees of squeezing and entanglement. Our work will provide improved schemes for designing COPAs to efficiently produce high-quality squeezed and entangled states, which have potential applications in quantum-information processing.
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This paper is concerned with linear quantum networks of NNN nondegenerate optical parametric amplifiers (NOPAs), with NNN up to 6, which are interconnected in a coherent feedback chain. Each network connects two communicating parties (Alice and Bob) over two transmission channels. In previous work we have shown that a dual-NOPA coherent feedback network generates better Einstein-Podolsky-Rosen (EPR) entanglement (i.e., more two-mode squeezing) between its two outgoing Gaussian fields than a single NOPA, when the same total pump power is consumed and the systems undergo the same transmission losses over the same distance. This paper aims to analyze stability, EPR entanglement between two outgoing fields of interest, and bipartite entanglement of two-mode Gaussian states of cavity modes of the NNN-NOPA networks under the effect of transmission and amplification losses, as well as the effect of time delays on the outgoing fields. It is numerically shown that, in the absence of losses and delays, the network with more NOPAs in the chain requires less total pump power to generate the same degree of EPR entanglement. Moreover, we report on the internal entanglement synchronization that occurs in the steady state between certain pairs of Gaussian oscillator modes inside the NOPA cavities of the networks.
This paper presents formulae for Einstein-Podolsky-Rosen (EPR) entanglement generated from N nondegenerate optical parametric amplifiers (NOPAs) interconnected in a linear coherent feedback (CFB) chain in the idealized lossless scenario and infinite bandwidth limit. The lossless scenario sets the ultimate EPR entanglement (two-mode squeezing) that can be achieved by this linear chain of NOPAs while the infinite bandwidth limit simplifies the analysis but gives an accurate approximation to the EPR entanglement at low frequencies of interest. Two adjustable phase shifts are placed at the outputs of the system to achieve the best EPR entanglement by selecting appropriate quadratures of the output fields.