Fast multi-copy entanglement purification with linear optics

Lan Zhou, Shuaishuai Zhang, Wei Zhong +1 more

Yu‐Bo Sheng, Gui Lu Long, Fu‐Guo Deng

Chun Cai, Lan Zhou, Yu‐Bo Sheng

We describe an entanglement purification protocol for a polarization Bell state. Different from the previous protocols, it does not require the controlled-not gate, and only uses linear optical elements to complete the task. This protocol requires multi-copy degraded mixed states, which can make this protocol obtain a high fidelity in one purification step. It can also be extended to purify the multi-photon Greenberger–Horne–Zeilinger (GHZ) state. This protocol may be useful in future long-distance communication.

Dong Pyo Chi, Tae‐Wan Kim, Soojoon Lee

Shuaishuai Zhang, Qi Ze Shu, Lan Zhou +1 more

Entanglement purification is to distill the high quality entanglement from the low quality entanglement with local operations and classical communications. It is one of the key technologies in long-distance quantum communication. We discuss an entanglement purification protocol (EPP) with spontaneous parametric down conversion (SPDC) sources, in contrast to previous EPP with multi-copy mixed states, which requires ideal entanglement sources. We show that the SPDC source is not an obstacle for purification, but can benefit the fidelity of the purified mixed state. This EPP works for linear optics and is feasible in current experiment technology.

Ulrik L. Andersen, Radim Filip, Jaromı́r Fiurášek +2 more

We propose a scheme for optimal Gaussian purification of coherent states from several imperfect copies. The proposal is experimentally demonstrated for the case of two copies of a coherent state sent through independent noisy channels. Our purification protocol relies on only linear optics and an ancilla vacuum state, rendering this approach an interesting alternative to the more complex protocols of entanglement distillation and quantum error correction.