Polarization-Multiplexed Quadrature Amplitude Modulation for Continuous-Variable Quantum Key Distribution
We propose a continuous-variable quantum key distribution (CV-QKD) scheme by using polarization-multiplexing (Pol-Mux) technique. As an effective way to promote spectral efficiency, quadrature amplitude modulation (QAM) has ability to provide substantial capacity. However, it may encounter the problem when discriminated symbols with increasing d. The star-QAM with different ring radii is utilized to tolerate greater phase jitter and improve the stability. In the proposed scheme, an optical phase reference signal is multiplexed to the quantum signal through the optical fiber to provide phase reference for local oscillator signal, which enables secure key distribution. However, the quadrature amplitude modulation could obtain the high modulation efficiency at the cost of increased complexity. And we utilize the low-density parity-check (LDPC) codes with little computational cost reconciliation scheme to deal with the extra data. From the numerical results, the proposed scheme achieves a good performance in terms of the key generation rate. The secure bound is derived with the presence of a Gaussian channel and the analysis shows the performance of the proposed scheme can be further improved by altering the effective parameters.
KeywordsContinuous-variable quantum key distribution Polarization-multiplexed QAM LDPC
This work is supported by the National Natural Science Foundation of China (Grant Nos. 61379153, 61572529).
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