General Quantum Entanglement Purification Protocol using a Controlled‐Phase‐Flip Gate

• Published in: Annalen der Physik 2020-04, Vol.532 (4), p.n/a
• Main Authors: Lu, Lu‐Cong, Ren, Bao‐Cang, Wang, Xin, Zhang, Mei, Deng, Fu‐Guo
• Format: Article
• Language: English
• Subjects: Accuracy; controlled‐phase‐flip gate; Entangled states; entanglement purification; Errors; Purification; Quantum dots; Quantum entanglement; quantum information; Quantum mechanics
• ISSN: 0003-3804; 1521-3889
• DOI: 10.1002/andp.202000011

Entanglement purification is an important method to guarantee the fidelity of long‐distance quantum communication. Here, a general entanglement purification protocol (EPP) for mixed state with bit‐flip error and phase‐flip error is proposed, resorting to unilateral operations and a controlled‐phase‐flip (CPF) gate. The CPF gate is working with a high fidelity under balance condition of quantum dot embedded in a double‐sided optical cavity. This general EPP scheme can purify the mixed state with both bit‐flip error and phase‐flip error to a high fidelity entangled state relatively fast in some regimes, owing to the unilateral operations and high‐fidelity CPF gate, which can largely decrease the resource consumption. This general EPP provides a convenient way for increasing the entanglement of different quantum systems, which has great potential for guaranteeing the fidelity of long‐distance quantum communication in the future. A general two‐photon entanglement purification protocol is proposed for mixed state with bit‐flip and phase‐flip errors, using unilateral operations and a controlled phase‐flip gate constructed by the balance condition of a double‐sided quantum dot cavity system. This protocol can purify the mixed state relatively fast in some regimes, and it provides a convenient way for increasing the entanglement of different quantum systems.