Abstract
We propose a multiple-input multiple-output (MIMO) quantum key distribution (QKD) scheme for terahertz (THz) frequency applications operating at room temperature. Motivated by classical MIMO communications, a transmit-receive beamforming scheme is proposed that converts the rank- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$r$ </tex-math></inline-formula> MIMO channel between Alice and Bob into <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$r$ </tex-math></inline-formula> parallel lossy quantum channels. Compared with existing single-antenna QKD schemes, we demonstrate that the MIMO QKD scheme leads to performance improvements by increasing the secret key rate and extending the transmission distance. Our simulation results show that multiple antennas are necessary to overcome the high free-space path loss at THz frequencies. We demonstrate a non-monotonic relation between performance and frequency, and reveal that positive key rates are achievable in the 10–30 THz frequency range. The proposed scheme can be used for both indoor and outdoor QKD applications for beyond fifth generation ultra-secure wireless communications systems.
Highlights
W ITH the exponential increase in demand for high data rates, various physical layer solutions, including multiple-input multiple-output (MIMO) systems and the utilization of the terahertz (THz) frequency band have been proposed for beyond fifth generation (B5G) applications [1].In addition to the requirement of a high data rate, future communication systems are expected to deliver secure and encrypted data transmission to improve reliability and data privacy
We propose a MIMO continuous variable QKD (CVQKD) scheme to improve the secret key rate and the maximum transmission distance of a CVQKD system operating at THz frequencies
We propose a MIMO CVQKD system model and a singular-value decomposition (SVD) based transmit-receive beamforming scheme
Summary
W ITH the exponential increase in demand for high data rates, various physical layer solutions, including multiple-input multiple-output (MIMO) systems and the utilization of the terahertz (THz) frequency band have been proposed for beyond fifth generation (B5G) applications [1]. In addition to the requirement of a high data rate, future communication systems are expected to deliver secure and encrypted data transmission to improve reliability and data privacy In this regard, quantum key distribution (QKD) has been proposed to meet the challenges of developing highly secure communication links [2]. We propose a MIMO CVQKD system model and a singular-value decomposition (SVD) based transmit-receive beamforming scheme This model generalizes the SISO beam-splitter channel model for the THz MIMO channel by utilizing the MIMO quantum back-scatter communication framework of [11]. We present new analytical expressions for the secret key rate of the proposed MIMO QKD scheme This demonstrates the non-trivial dependence of performance on the operating frequency, which we show is nonmonotonic. N (μ, Σ) denotes the real multivariate Gaussian distribution with mean vector μ and covariance matrix Σ
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