Multipartite entanglement concentration for nitrogen-vacancy center and microtoroidal resonator system

Abstract

We describe a high efficient entanglement concentration protocol (ECP) for multi-particle less-entangled nitrogen-vacancy (N-V) center and microtoroidal resonator system. In the ECP, we only require one pair of less-entangled state, two auxiliary N-V center in microcavities and some single photons. After the photon passing through the microcavity, by measuring the polarization of the photon, a maximally entangled W state can be obtained with some success probability. This ECP does not need to destroy the solid qubit, which makes it more feasible. Moreover, by resorting to more single photons, it can be repeated to reach a high success probability. These features make this ECP useful in current long-distance quantum communications. Quantum communication deals with the transmission and exchange of quantum information between distant nodes of a network [1]. Such transmission and exchange of quantum information has potential application in the secret transfer of classical messages by means of quantum key distribution [2-5], teleportation [6][7][8], quantum denescoding [9][10][11], quantum secret sharing [12][13][14], quantum state sharing [15][16][17], quantum secure direct communication [18][19][20][21][22], and other protocols [23][24][25][26][27]. The basic principle of quantum communication is to generate nearly perfect entangled states between distant locations. Quantum repeaters are used to extend the length of quantum channel, which is used to resist the photon loss. On the other hand, the perfect entangled state will also be degraded because of the environment noise. The maximally entangled state will become a mixed state or a less-entangled states. Entanglement purification is to distill some high quality entangled states from a large ensembles of low quality entangled states, which has been widely studied [28][29][30][31][32][33][34][35]. *Corresponding author (email: zhoul@njupt.edu.cn) Entanglement concentration is to recover some maximally entangled states from a large ensembles of pure lessentangled ensembles . In 1996, Bennett et al. [36] described an entanglement concentration protocol (ECP) with collective measurement. The ECP with entanglement swapping was developed by Shi et al. [37]. The ECPs with linear optics were proposed in 2001 [38,39]. These protocols were developed in 2008 with the help of cross-Kerr nonlinearity [40][41][42]. Most of the ECPs focused on the photons [38][39][40][41][42][43][44][46][47][48][49][50][51]. During the past few years, the ECPs for solid entangled systems were also proposed, such as the ECP for quantum dot and microcavity coupling system [54,55], electrons [56][57][58], atoms [59] and so on [62][63][64][65].Recently, the nitrogen-vacancy (N-V) defect center in diamond becomes a promising candidate for solid quantum information processing. The N-V centers are negatively charged with six electrons from the nitrogen [66,67]. The vacancy are surrounded by three carbons. A lot of theoretical and experimental works have been devoted into such systems, for it provide...

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