Long Distance Quantum Communication Over a Noisy Channel

Hans J. Briegel

Chao Han, Zheng-Wei Zhou, Guang‐Can Guo

The creation of a quantum network is an important goal of quantum information processing. Long distance quantum communication with high fidelity is the main obstacle in achieving this goal. A scheme to transmit qubits without fidelity decrease over the noisy channel is presented. Using the idea of ‘time-bin entanglement’, the scheme works without any auxiliary particles and there is no resources increase with the length of the channel. A protocol proposed by Kalamidas [18] is suitable to realize our scheme with the current experimental technology.

Sébastien Perseguers, Liang Jiang, Norbert Schuch +4 more

We consider the problem of creating a long-distance entangled state between two stations of a network, where neighboring nodes are connected by noisy quantum channels. We show that any two stations can share an entangled pair if the effective probability for the quantum errors is below a certain threshold, which is achieved by a local encoding of the qubits and a global bit-flip correction. In contrast to the conventional quantum-repeater schemes, we do not need to store the qubits in quantum memory for a long time: our protocol is a one-shot process (i.e., the elementary entangled pairs are used only once) involving one-way classical communication. Furthermore, the overhead of local resources increases only logarithmically with the size of the network, making our proposal favorable to long-distance quantum communication.

L.-M. Duan, Mikhail D. Lukin, P. Zoller +1 more

Nicoló Lo Piparo

Bao‐Cang Ren, Fang‐Fang Du, Fu‐Guo Deng

Hyperentanglement is a promising resource in quantum information processing, especially for increasing the channel capacity of long-distance quantum communication. Hyperentanglement purification is an important method to obtain high-fidelity nonlocal hyperentangled states from mixed hyperentangled states in a long-distance quantum communication process with noisy channels. Here, we present a two-step hyperentanglement purification protocol for nonlocal mixed hyperentangled states with polarization bit-flip errors and spatial-mode phase-flip errors, resorting to polarization-spatial phase-check quantum nondemolition detectors and the quantum-state-joining method (QSJM). With QSJM, the protocol can preserve the states that are discarded in the previous hyperentanglement purification protocols. It has the advantage of a high efficiency, and it is useful for improving the entanglement of photon systems with several degrees of freedom in long-distance high-capacity quantum communication.