Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:quant-ph/0611059 · Applied Physics Letters

Experimental quantum key distribution with active phase randomization

Yi Zhao, Bing Qi, Hoi-Kwong Lo

Published Jan 22, 2007• 71 citations
arXivHTMLPDF

Abstract

Phase randomization is an important assumption made in many security proofs of practical quantum key distribution (QKD) systems. Here, the authors present the first experimental demonstration of QKD with reliable active phase randomization. One key contribution is a polarization-insensitive phase modulator, which they added to a commercial phase-coding QKD system to randomize the global phase of each bit. They also proposed a useful method to verify the phase randomization experimentally. Their result shows very low quantum bit error rate (<1%). They expect this active phase randomization process to be a standard part in future QKD setups due to its significance and feasibility.

DOI
10.1063/1.2432296

Related papers

Experimental quantum key distribution with active phase randomization

Yi Zhao, Bing Qi, Hoi‐Kwong Lo

Phase-randomization is an important assumption in many security proofs of practical quantum key distribution (QKD) systems. Here, we present the first experimental QKD with reliable active phase-randomization. A polarization-insensitive phase-modulator is designed for our experiment.

Quantum Electronics and Laser Science Conference•May 1, 2007•9 citations

Experimental demonstration of phase-remapping attack in a practical quantum key distribution system

Feihu Xu, Bing Qi, Hoi‐Kwong Lo

Quantum key distribution (QKD) can, in principle, provide unconditional security based on the fundamental laws of physics. Unfortunately, a practical QKD system may contain overlooked imperfections and may thus violate some of the assumptions in the security proofs of QKD. It is important to explore these assumptions. One key assumption is that the sender (Alice) can prepare the required quantum states without errors. However, such an assumption may be violated in a practical QKD system. In this paper, we perform a proof-of-principle experiment to demonstrate a technically feasible 'intercept- and-resend' attack that exploits such a security loophole in a commercial 'plug & play' QKD system. The resulting quantum bit error rate is 19.7%, which is substantially lower than the well-known 25% error rate for an intercept-and-resend attack in BB84. The attack we utilize is the phase-remapping attack (Fung et al 2007 Phys. Rev. A 75 32314) proposed by our group.

arXiv:1005.2376•New Journal of Physics•Nov 11, 2010•331 citations

High-speed polarization coding in a quantum key distribution system

Yadong Wei, Yunxia Wu, Zhilie Tang +3 more

We present a high-speed polarization-coding method, which makes use of phase modulation, for use in a quantum key distribution (QKD) system. This technique has been introduced into a QKD system for the first time. A completely quantum mechanical method is employed to describe quantum information processing here. Experiments on a balanced element for polarization coding by phase modulation are described in detail. The experimental results demonstrate that this technique can encode or decode polarization at high speed (with feasibility in the GHz range) and low voltage (a few volts) successfully.

International Conference on Electronics and Optoelectronics•Jul 1, 2011•0 citations

Experimental demonstration of passive-decoy-state quantum key distribution with two independent lasers

Shi‐Hai Sun, Guang‐Zhao Tang, Chunyan Li +1 more

The decoy-state method could effectively enhance the performance of quantum key distribution (QKD) with a practical phase randomized weak coherent source. Although active modulation of the source intensity is effective and has been implemented in many experiments, passive preparation of decoy states is also an important addition to the family of decoy-state QKD protocols. In this paper, following the theory of Curty et al. [Phys. Rev. A 81, 022310 (2010)], we experimentally demonstrate the phase-encoding passive-decoy-state QKD with only linear optical setups and threshold single-photon detectors. In our experiment, two homemade independent pulsed lasers, with visibility of Hong-Ou-Mandel interference $0.53(\ifmmode\pm\else\textpm\fi{}0.003)$, have been implemented and used to passively generate the different decoy states. Finally, a secret key rate of $1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$/pulse is obtained with 10-km commercial fiber between Alice and Bob.

arXiv:1609.02653•Physical Review A•Sep 27, 2016•15 citations

Optimized Polarization Encoder with High Extinction Ratio for Quantum Key Distribution System

Pengcheng Wang, Qianqian Zhang, Huanwen Xie +1 more

Polarization encoding is a promising approach for practical quantum key distribution (QKD) systems due to its simple encoding and decoding methodology. In this study, we propose a self-compensating polarization encoder (SCPE) based on a phase modulator, which can be composed of commercial off-the-shelf (COT) devices. We conducted a proof-of-concept experiment to test the SCPE, which demonstrated an in-system quantum bit error rate (QBER) of 0.53% and long-term running stability without any active adjustments. Additionally, we conducted experiments with transmission over commercial fiber spools of lengths up to 100 km and obtained a secure finite key rate of 3 kbps. Our polarization encoder is a promising solution for various polarization encoding protocols, including BB84, MDI, and RFI.

Electronics•Apr 14, 2023•2 citations

Experimental demonstration of a local active phase compensation method for a phase encoding quantum key distribution system

Yue Zhang, Junyue Yin, Huiqing Zhao +7 more

An efficient phase stabilization method is required in quantum key distribution (QKD) systems for stability in practical applications. The existing active phase compensation method has limitations in multi-node network applications, especially in network-scale applications based on measurement-device-independent QKD systems. In this study, we propose a local active phase compensation scheme that can realize phase compensation independently for each interferometer node. We performed experimental demonstrations in the BB84 phase encoding system based on a Faraday-Michelson interferometer. The average QBER rates of the system under two different forms of the reference light were found to be 1.9% and 1.6%. This scheme can also be applied to other QKD systems and has potential for application in future quantum communication networks.

Applied Optics•Aug 19, 2022•2 citations
Phase randomization is an important assumption made in many security proofs of practical quantum key distribution (QKD) systems. Here, the authors present the first experimental demonstration of QKD with reliable active phase randomization. One key contribution is a polarization-insensitive phase modulator, which they added to a commercial phase-coding QKD system to randomize the global phase of each bit. They also proposed a useful method to verify the phase randomization experimentally. Their result shows very low quantum bit error rate (<1%). They expect this active phase randomization process to be a standard part in future QKD setups due to its significance and feasibility.
Quantum key distribution (QKD) can, in principle, provide unconditional security based on the fundamental laws of physics. Unfortunately, a practical QKD system may contain overlooked imperfections and may thus violate some of the assumptions in the security proofs of QKD. It is important to explore these assumptions. One key assumption is that the sender (Alice) can prepare the required quantum states without errors. However, such an assumption may be violated in a practical QKD system. In this paper, we perform a proof-of-principle experiment to demonstrate a technically feasible 'intercept- and-resend' attack that exploits such a security loophole in a commercial 'plug & play' QKD system. The resulting quantum bit error rate is 19.7%, which is substantially lower than the well-known 25% error rate for an intercept-and-resend attack in BB84. The attack we utilize is the phase-remapping attack (Fung et al 2007 Phys. Rev. A 75 32314) proposed by our group.
We present a high-speed polarization-coding method, which makes use of phase modulation, for use in a quantum key distribution (QKD) system. This technique has been introduced into a QKD system for the first time. A completely quantum mechanical method is employed to describe quantum information processing here. Experiments on a balanced element for polarization coding by phase modulation are described in detail. The experimental results demonstrate that this technique can encode or decode polarization at high speed (with feasibility in the GHz range) and low voltage (a few volts) successfully.
The decoy-state method could effectively enhance the performance of quantum key distribution (QKD) with a practical phase randomized weak coherent source. Although active modulation of the source intensity is effective and has been implemented in many experiments, passive preparation of decoy states is also an important addition to the family of decoy-state QKD protocols. In this paper, following the theory of Curty et al. [Phys. Rev. A 81, 022310 (2010)], we experimentally demonstrate the phase-encoding passive-decoy-state QKD with only linear optical setups and threshold single-photon detectors. In our experiment, two homemade independent pulsed lasers, with visibility of Hong-Ou-Mandel interference $0.53(\ifmmode\pm\else\textpm\fi{}0.003)$, have been implemented and used to passively generate the different decoy states. Finally, a secret key rate of $1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$/pulse is obtained with 10-km commercial fiber between Alice and Bob.
Polarization encoding is a promising approach for practical quantum key distribution (QKD) systems due to its simple encoding and decoding methodology. In this study, we propose a self-compensating polarization encoder (SCPE) based on a phase modulator, which can be composed of commercial off-the-shelf (COT) devices. We conducted a proof-of-concept experiment to test the SCPE, which demonstrated an in-system quantum bit error rate (QBER) of 0.53% and long-term running stability without any active adjustments. Additionally, we conducted experiments with transmission over commercial fiber spools of lengths up to 100 km and obtained a secure finite key rate of 3 kbps. Our polarization encoder is a promising solution for various polarization encoding protocols, including BB84, MDI, and RFI.
An efficient phase stabilization method is required in quantum key distribution (QKD) systems for stability in practical applications. The existing active phase compensation method has limitations in multi-node network applications, especially in network-scale applications based on measurement-device-independent QKD systems. In this study, we propose a local active phase compensation scheme that can realize phase compensation independently for each interferometer node. We performed experimental demonstrations in the BB84 phase encoding system based on a Faraday-Michelson interferometer. The average QBER rates of the system under two different forms of the reference light were found to be 1.9% and 1.6%. This scheme can also be applied to other QKD systems and has potential for application in future quantum communication networks.