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Simultaneous quantum and classical communication using continuous variable

Bing Qi

Published Jun 8, 2016• 1 citation
OpenAlex

Abstract

Conventionally, classical optical communication systems employing strong laser pulses and quantum key distribution (QKD) systems working at single-photon levels are quite different communication modalities. Dedicated devices are commonly required to implement QKD. Here we show these two can be implemented simultaneously using the same information carriers. More specially, we propose a coherent communication scheme where both the binary bits for a classical communication protocol and Gaussian distributed random numbers for a QKD protocol are encoded on the same weak coherent pulses, and decoded by the same coherent receiver. Simulation results based on realistic system parameters show that both deterministic classical communication with a bit error rate of 10^{-9} and secure key distribution can be achieved over 30km single mode fibers. It is conceivable that in the future coherent optical communication network, QKD is operated in the background of classical communication at negligible cost.

Related papers

Simultaneous classical communication and quantum key distribution using continuous variables

Bing Qi

Presently, classical optical communication systems employing strong laser pulses and quantum key distribution (QKD) systems working at single-photon levels are very different communication modalities. Dedicated devices are commonly required to implement QKD. In this paper, we propose a scheme which allows classical communication and QKD to be implemented simultaneously using the same communication infrastructure. More specially, we propose a coherent communication scheme where both the bits for classical communication and the Gaussian distributed random numbers for QKD are encoded on the same weak coherent pulse and decoded by the same coherent receiver. Simulation results based on practical system parameters show that both deterministic classical communication with a bit error rate of ${10}^{\ensuremath{-}9}$ and secure key distribution could be achieved over tens of kilometers of single-mode fibers. It is conceivable that in the future coherent optical communication network, QKD will be operated in the background of classical communication at a minimal cost.

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Conventionally, classical optical communication systems employing strong laser pulses and quantum key distribution (QKD) systems working at single-photon levels are quite different communication modalities. Dedicated devices are commonly required to implement QKD. Here we show these two can be implemented simultaneously using the same information carriers. More specially, we propose a coherent communication scheme where both the binary bits for a classical communication protocol and Gaussian distributed random numbers for a QKD protocol are encoded on the same weak coherent pulses, and decoded by the same coherent receiver. Simulation results based on realistic system parameters show that both deterministic classical communication with a bit error rate of 10^{-9} and secure key distribution can be achieved over 30km single mode fibers. It is conceivable that in the future coherent optical communication network, QKD is operated in the background of classical communication at negligible cost.
Presently, classical optical communication systems employing strong laser pulses and quantum key distribution (QKD) systems working at single-photon levels are very different communication modalities. Dedicated devices are commonly required to implement QKD. In this paper, we propose a scheme which allows classical communication and QKD to be implemented simultaneously using the same communication infrastructure. More specially, we propose a coherent communication scheme where both the bits for classical communication and the Gaussian distributed random numbers for QKD are encoded on the same weak coherent pulse and decoded by the same coherent receiver. Simulation results based on practical system parameters show that both deterministic classical communication with a bit error rate of ${10}^{\ensuremath{-}9}$ and secure key distribution could be achieved over tens of kilometers of single-mode fibers. It is conceivable that in the future coherent optical communication network, QKD will be operated in the background of classical communication at a minimal cost.
At first sight, quantum key distribution (QKD) working at single-photon levels seems very different from classical optical communication using strong laser pulses. Surprisingly, in the simultaneous QKD and classical communication (SQCC) protocol, a single, coherent system can both transmit classical information and distribute a quantum key, but implementation has been impeded by its low tolerance of phase noise. The authors identify ``trusted'' noise from the coherent receiver, which cannot be accessed by an eavesdropper, and greatly improve the phase-noise tolerance of the SQCC protocol. Their findings suggest that the SQCC protocol could be truly practical for secure communication.
Classical and quantum communication protocols share similarities in terms of signal modulation, transmission, and reception, providing a basis for their integration. The integration of these protocols can lead to high-efficiency and low-cost performance by utilizing a single set of communication infrastructures to simultaneously achieve continuous-variable quantum key distribution and classical communication on a single wavelength. In this paper, we propose a simultaneous quantum and classical communication (SQCC) protocol based on multiparameter modulation, which combines pulse position modulation (PPM) for classical communication and Gaussian-distributed modulation (GM) for quantum key distribution, named GMCS-PPM-SQCC protocol. Classical information is transmitted using the arrival time parameter of the coherent state, while quantum key information is distributed through the two quadrature components of the coherent state. Coherent detection is used to detect all three parameters, and different data processing schemes are utilized to extract the corresponding information. We verified the feasibility of the protocol through simulations, discussed its secure transmission distance, bit error rate, and secret key rate in realistic scenarios. Our protocol has better phase noise tolerance than traditional SQCC protocol. It can further facilitates the integration of classical and quantum communication, and contributes to the deployment and application of QKD.
We propose a novel scheme for measurement-device-independent (MDI) continuous-variable quantum key distribution (CVQKD) by simultaneously conducting classical communication and QKD, which is called “simultaneous MDI-CVQKD” protocol. In such protocol, each sender (Alice, Bob) can superimpose random numbers for QKD on classical information by taking advantage of the same weak coherent pulse and an untrusted third party (Charlie) decodes it by using the same coherent detectors, which could be appealing in practice due to that multiple purposes can be realized by employing only single communication system. What is more, the proposed protocol is MDI, which is immune to all possible side-channel attacks on practical detectors. Security results illustrate that the simultaneous MDI-CVQKD protocol can secure against arbitrary collective attacks. In addition, we employ phase-sensitive optical amplifiers to compensate the imperfection existing in practical detectors. With this technology, even common practical detectors can be used for detection through choosing a suitable optical amplifier gain. Furthermore, we also take the finite-size effect into consideration and show that the whole raw keys can be taken advantage of to generate the final secret key instead of sacrificing part of them for parameter estimation. Therefore, an enhanced performance of the simultaneous MDI-CVQKD protocol can be obtained in finite-size regime.
We propose a new quantum communication scheme using quantum coherent states. In our scheme, classical information and the secret key are transmitted simultaneously without any loss of secret key rate performance, while only the secret key is transmitted in the conventional protocol. In our protocol, classical information is first modulated by pulse amplitude modulation (PAM). The secret key is then mapped by random Gaussian modulation and is added to the PAM symbol. The receiver decodes the classical information, treating the Gaussian signal as additive noise. The classical symbol is discarded from the received state after successive decoding of the classical information, and the secret key is then distilled by conventional protocol. We demonstrate that after the classical symbol is discarded, the remaining system is identical to the conventional quantum key distribution system. Our proposed scheme provides the same secret key rate as that of the conventional quantum key distribution system and provides an additional data rate of classical information.
Classical communication and quantum key distribution (QKD) share similarities in signal modulation, transmission, and reception, providing a foundation for their integration. This paper proposes a novel protocol for simultaneous quantum and classical communication in short-distance Continuous-Variable QKD (CV-QKD). The protocol employs polarization-state encoding of classical information with weak coherent states, allowing for the concurrent transmission of quantum and classical data without the need for classical optical pulses. A noise model is established to analyze the system’s excess noise under varying modulation variances, along with the performance of both classical and quantum communication. Simulation results indicate that our proposed protocol can achieve a secure key rate of no less than 1.05Mbps over a distance of 20km.