Faithful quantum entanglement purification and concentration using heralded high-fidelity parity-check detectors based on quantum-dot-microcavity systems

Entanglement purification and concentration are effective means to deal with the influence of noise on the coherence of entangled quantum systems, which enable us to carry out secure and efficient quantum communications. However, the reliability of parity check in parity-check-based entanglement purification and concentration schemes will inevitably affect the performance of the schemes. In this paper, we propose faithful entanglement purification and concentration schemes for polarization-entangled photon pairs, using heralded high-fidelity parity-check detectors (PCDs) constructed by double-sided quantum-dot-microcavity (QD-microcavity) systems and linear-optical elements. The PCD is based on the general interaction rule between the input photon and the QD-microcavity system, without the requirement of the system to strictly satisfy the specifically ideal conditions for giant circular birefringence, which makes it more realizable in practice. Moreover, the PCD can work in a failure-heralded and fidelity-robust fashion, so it can make a correct judgement on the parity mode of a two-photon system and has no destruction on the entangled state. Our schemes can therefore realize faithful entanglement purification and concentration by utilizing the PCD, without reducing the fidelity and entanglement degree of the obtained entangled-state ensemble. These features make our schemes more feasible and useful in quantum repeaters and quantum networks.