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Asia-Pacific Conference on Communications (APCC)

A new scheme for quantum key distribution in free-space

Guoqing Cui, Yuan Lü, Guihua Zeng

Published Oct 1, 2009• 6 citations
Publisher

Abstract

Quantum key distribution (QKD) has been proposed for decades. Many applications have been deployed recently for both wired and wireless networks. Especially for optical networks, QKD technique has a great development. But in free-space quantum key distribution still has a lot of problems such as a low bit rate. In this paper we propose a new scheme, combining MIMO (Multiple input multiple output) system and wireless networks for QKD in free-space networks. With the proposed approach, a higher bit rate QKD networks in free-space could be realized theoretically.

DOI
10.1109/apcc.2009.5375518

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Quantum key distribution (QKD) has been proposed for decades. Many applications have been deployed recently for both wired and wireless networks. Especially for optical networks, QKD technique has a great development. But in free-space quantum key distribution still has a lot of problems such as a low bit rate. In this paper we propose a new scheme, combining MIMO (Multiple input multiple output) system and wireless networks for QKD in free-space networks. With the proposed approach, a higher bit rate QKD networks in free-space could be realized theoretically.
Quantum key distribution (QKD) systems for use in future free-space optical communication links restrict communication to a low bit rate. In this paper, increasing the QKD bit rate using a communication system that includes a multiple-input-multiple-output quantum key distribution (MQKD) is proposed. Such a system can enable a number of receivers to communicate simultaneously with a number of transmitter elements, which consequently increases the overall QKD bit rate. However, due to scattering and turbulence in the atmospheric channel, this method may introduce interference effects when a photon transmitted from one transmitter element reaches the wrong detector element in the receiver. These interference effects reduce the system bit rate and increase the quantum bit error rate. A novel mathematical model for analyzing the effect of crosstalk and interference on the MQKD system performance is derived. The results of the analysis indicate that atmospheric effects impair performance. In order to mitigate the atmospheric effect, using several wavelengths simultaneously is suggested. Criteria to define the number of wavelengths that are required to achieve a given performance are also provided.
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-rrrMIMO channel between Alice and Bob intorrrparallel 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.
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-rrr MIMO channel between Alice and Bob into rrr 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.
Quantum communication is a process of quantum key distribution （QKD）. Current QKD technology restricts communication to a low bit rate. To improve the QKD bit rate and develop high rate and capacity, we propose a multiple-input-multiple-output quantum key distribution system. However, quantum field itself inevitably involves quantum noise （which is determined by the quantum mechanics ）, which restrains the increase of capacity, and limits space resource utilization, that is, the problem of spatial degrees of freedom arises. The quantumization of the photon field and the electromagnetic wave equation satisfying the Schrdinger equation condition are adopted to investigate the upper bound of the spatial degrees of freedom for MIMO quantum channels, which will provide theoretical support and technical basis for developing robust space time processing algorithm for MIMO quantum communication and designing high performance systems.
Quantum key distribution (QKD) systems are being developed for possible use in future free space optical communication links to provide high security transmissions. However, these systems restrict the communication to a low bit-rate. To increase the QKD bit rate we suggest implementing a communication system which includes both optical detector and transmitter arrays. The mathematical description of this scheme involves a multi-input multi-output (MIMO) model. The optical detector and transmitter arrays enable the receiver to communicate simultaneously with a number of transmitter elements, which consequently increases the QKD bit rate. However, this method may introduce interference effects when a photon transmitted from one transmitter element reaches the wrong detector element in the receiver, due to scattering and turbulence in the atmospheric channel. This crosstalk and interference reduce the overall system bit rate and increase the quantum bit error rate (QBER). Analyzing the effect of crosstalk and interference on the system performance is accomplished by using the optical transfer function (OTF) theory.
Quantum safety communications is a process of quantum key distribution （QKD）. Current QKD technology restricts transmission to a low bit rate. To improve the QKD bit rate and develope high rate and large capacity, we propose a multiple-input-multiple-output（MIMO） quantum key distribution system. The Wigner operator of multi-photon entangled states in MIMO quantum key distribution channel is presented. As a result, the Wigner function of multi-photon double-model squeezed entangled sates and MIMO quantum key distribution channel capacity are also obtained, which will provide theoretical support and technical basis for developing robust space-time processing algorithm of MIMO quantum safety communications and designing optimum high performance system of MIMO quantum key distribution.