We propose a multiple-input multiple-output (MIMO) quantum key distribution (QKD) scheme for improving the secret key rates and increasing the maximum transmission distance for terahertz (THz) frequency range applications operating at room temperature. We propose a transmit beamforming and receive combining scheme that converts the rank-$r$ MIMO channel between Alice and Bob into $r$ parallel lossy quantum channels whose transmittances depend on the non-zero singular values of the MIMO channel. The MIMO transmission scheme provides a multiplexing gain of $r$, along with a beamforming and array gain equal to the product of the number of transmit and receive antennas. This improves the secret key rate and extends the maximum transmission distance. Our simulation results show that multiple antennas are necessary to overcome the high free-space path loss at THz frequencies. Positive key rates are achievable in the $10-30$ THz frequency range that can be used for both indoor and outdoor QKD applications for beyond fifth generation ultra-secure wireless communications systems.
翻译:我们提议了一个多投入多输出量子钥匙分配(QKD)计划,用于提高秘密关键率,提高在室温下运行的Thahertz(Thz)频率应用的最大传输距离。我们提议了一个传输光束和接收组合方案,将Alice和Bob之间的一级-美元MIMO频道转换成美元平行损失量子频道,其传输取决于MIMO频道的非零单值。MIMO传输计划提供了多氧化收益1美元,以及一个波形和阵列增益,相当于传输和接收天线数量的产品。这改进了秘密密钥率,扩大了最大传输距离。我们的模拟结果表明,要克服Thz频率的高自由空间路径损失,多天线天线是必需的。在可用于第五代超安全无线通信系统的室内和户外可使用10-30美元的Thz频率范围内,可以实现正关键率。