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arXiv:1101.5995

Quantum key distribution based on frequency-time coding: security and feasibility

Bing Qi

Published Jan 31, 2011• 5 citations
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Abstract

We establish a security proof of frequency-time coding quantum key distribution (FT-QKD) protocol by showing its connection to the squeezed state quantum key distribution protocol, which has been proven to be unconditionally secure. We also extend the prepare-and-measure FT-QKD protocol to an entanglement based FT-QKD protocol which is more appealing in practice. Furthermore, we propose a correlated frequency measurement scheme of entangled photon pair by using time resolving single photon detector. Simulation results show that the FT-QKD protocol can be implemented with today's technology.

DOI
10.48550/arxiv.1101.5995

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We establish a security proof of frequency-time coding quantum key distribution (FT-QKD) protocol by showing its connection to the squeezed state quantum key distribution protocol, which has been proven to be unconditionally secure. We also extend the prepare-and-measure FT-QKD protocol to an entanglement based FT-QKD protocol which is more appealing in practice. Furthermore, we propose a correlated frequency measurement scheme of entangled photon pair by using time resolving single photon detector. Simulation results show that the FT-QKD protocol can be implemented with today's technology.
We introduce a novel time-frequency quantum key distribution (TFQKD) scheme based on photon pairs entangled in these two conjugate degrees of freedom. The scheme uses spectral detection and phase modulation to enable measurements in the temporal basis by means of time-to-frequency conversion. This allows large-alphabet encoding to be implemented with realistic components. A general security analysis for TFQKD with binned measurements reveals a close connection with finite-dimensional QKD protocols and enables analysis of the effects of dark counts on the secure key size.
Quantum key distribution technology refers to a method to share keys between communication parties by transmitting quantum states in public channels. Although unconditional security is the main advantage of QKD, its application prospect has been controversial in practical implementation due to the potential security risks caused by device imperfections. Fortunately, the measurement device independent quantum key distribution protocol removes the vulnerability of all measurement devices and greatly improves the practical security of the quantum key distribution system. However, the security key rate of this protocol is still lower than that of other quantum key distribution protocols. At present, using high-dimensional coding to improve the performance of the quantum key distribution protocol has been proved in theory and experiment, and recently, it has been proposed to use high-dimensional coding to improve the performance of measurement device independent quantum key distribution protocol, but because these protocols have higher requirements for the laboratory equipment performance, that the high-dimensional encoding is applied to the aforementioned protocol still has many difficulties in practical application. In this paper, we propose a hybrid coding based on the polarization and two-degree phase of freedom measurement device independent quantum key distribution protocol. In the first place in an ideal case, we introduce in detail the protocol decoding rules, then introduce 4intensity decoy-state method to solve the problem of actual light source multiphoton, in addition we also consider the statistical fluctuation effect under the condition of limited code length, channel loss, actual dark count of single photon detector and detection efficiency problem. Finally, the optimal security code rate and its corresponding optimal parameters are obtained by full parameter optimization method, And the numerical simulation results show that the security key rate of this protocol is increased by 50% by considering the practical implementation. We point out that compared with other measurement device independent quantum key distribution protocol, the proposed agreement requires local users only to have a phase encoding device and a polarization coding device, and 4 single photon detectors for detecting side. The proposed device can use the existing experimental condition, beyond that, compared with the time encoding based high dimensional measurement device independent quantum key distribution protocol, the proposed protocol possesses the advantage that the rate of system security key can be increased without increasing the repetition frequency of users. It is proved that this protocol has great application value in the future field of quantum communication, especially, in the field of quantum network communication.
For secure practical systems, quantum key distribution (QKD) must provide high key rates over long distances. Time-entanglement-based QKD promises to increase the secret key rate and distribution distances compared to other QKD implementations. This article describes the major steps in QKD protocols, focusing on the nascent QKD technology based on high-dimensional time-bin entangled photons. We overview state-of-the-art from the information and coding theory perspective. In particular, we discuss the key rate loss due to single-photon detector imperfections. We hope the open questions posed and discussed in this paper will inspire information and coding theorists to contribute to and impact fledgling quantum applications and influence future quantum communication systems.
We present a composable security proof, valid against arbitrary attacks and including finite-size effects, for a high dimensional time-frequency quantum key distribution (TFQKD) protocol based upon spectrally entangled photons. Previous works have focused on TFQKD schemes as it combines the impressive loss tolerance of single-photon QKD with the large alphabets of continuous variable (CV) schemes, which enables the potential for more than one bit of secret key per transmission. However, the finite-size security of such schemes has only been proven under the assumption of collective Gaussian attacks. Here, by combining recent advances in entropic uncertainty relations for CVQKD with decoy state analysis, we derive a composable security proof that predicts key rates on the order of Mbits/s over metropolitan distances (40km or less) and maximum transmission distances of up to 140km.
Entanglement is an essential ingredient in many quantum communication protocols. In particular, entanglement can be exploited in quantum key distribution (QKD) to generate two correlated random bit strings whose randomness is guaranteed by the non-local property of quantum mechanics. While QKD protocols based on polarization and time-bin entanglement have been widely investigated, secure key distribution based on frequency-bin entangled photon sources have received only minor attentions.Here we experimentally implement the BBM92 protocol using a frequency-bin encoded entangled state, generated by an integrated source of photon pairs in a silicon photonic chip. We execute a passive basis selection scheme and simultaneously record sixteen projective measurements over two mutually unbiased basis sets. An adaptive rotation of the measurement base is introduced to compensate the random relative phase fluctuation between the two 15-GHz-spaced frequency bins in a fiber spool.Stable transmission over a 26 km fiber spool is demonstrated with a secret key rate ≥ 4.5 bit/s.