Optical-frequency-comb-based multichannel parallel continuous-variable quantum network coding

Carlos Andrés Gonzalez Arciniegas

Tianai Zhou, Gang Xu, Yewei Guo +4 more

Quantum network coding provides a solution for information transmission at bottleneck channels. However, the single-path scheduling approach is hampered in the face of massive data transmission demands, which is particularly challenging in large-scale network communication scenarios. Here we propose a continuous-variable quantum network coding (CVQNC) scheme for parallel transmission of multiple quantum states based on optical frequency combs. The quantum communication channel is naturally constructed due to the nonclassical correlations exhibited by the symmetric sideband modes at around half the pump frequency on the squeezed field. Source nodes with preshared multiplex entanglement enable the transmission of multiple quantum states in parallel and simultaneously, which increases the channel capacity of the network and relieves the single-path transmission pressure. In particular, fidelity is calculated as a critical measure of transmission performance, and we provide a method to increase fidelity using photon catalysis, along with squeezing parameters and beam splitter transmittance for non-Gaussian source states at optimal fidelity. Furthermore, the channel capacity and fidelity of the CVQNC system are predicted on the basis of the $k$-nearest neighbor algorithm, and the predicted data match well with the actual derivation.

Tao Shang, Jianwei Liu

Tao Shang, Ke Li, Jianwei Liu

Xia Yan, Tianai Zhou, Yongxin Feng +3 more

ABSTRACT Continuous‐variable quantum network coding (CVQNC) faces several challenges when extended to large scale scenarios, including the insufficient channel capacity, low entanglement generation efficiency, and degradation of entanglement under channel loss. In this study, a high‐capacity CVQNC scheme based on microcavity frequency combs is proposed over the butterfly network, which enables parallel quantum information transmission among multiple user pairs by exploiting network coding at the bottleneck link. Furthermore, an entanglement enhancement strategy combining mode multiplexing with quantum scissors is introduced to reduce the entanglement degradation caused by channel loss. The results show that the proposed scheme improves the entanglement enhancement efficiency, channel capacity, transmission fidelity, and security while scaling to a larger number of users.

Yijun Wang, Yiyu Mao, Wenti Huang +2 more

Continuous-variable quantum key distribution (CVQKD) provides an approach for secure communication in optical fiber communication systems. However, its practical implementation has been hindered by low secret key bit rates that are usually limited to several bits/s to hundreds of kbits/s at distances of more than 25 kilometers. In this paper, we use a pair of optical frequency combs (OFCs) for both multiple parallel transmission and coherent reception, which assign multiple sub-channels involving multiple independent secret keys in a single fiber to increase the key bit rate. The first and last sub-channels are selected for propagating phase references to compensate the phase offset between two free-running combs. We analyze possible excess noise caused by dispersive walk-off in the transmission, imperfect phase compensation in the reception and photon leakage from the phase references. Compared to the previous single-channel CVQKD method, simulation results show more than a factor of 20 increase in the secret key rate at a transmission distance of 35 km and the number of comb lines of 35.