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

IEEE Photonics Technology Letters

Polarization-Multiplexed Phase Modulation of Single Photons in a Sagnac Interferometer

Geping Liu, Yan Liang, Yuanjin Chen, Heping Zeng

Published Jul 12, 2017• 0 citations
Publisher

Abstract

Polarization-multiplexed phase modulation was demonstrated in a Sagnac interferometer for polarization-auto-compensating quantum key distribution. The Sagnac interferometer was composed of a polarization beam splitter to split the signal pulses into clockwise and counter-clockwise beams of different polarizations, a Faraday rotator to rotate the polarizations of the split clockwise and counter-clockwise beams, and two phase-modulators asymmetrically set in the Sagnac ring. With this structure, the delays of the electronic triggering signals for the two phase-modulators could be set separately, reducing the difficulty in the setup and achieving more precise phase modulation on different polarized beams. Such polarization-multiplexed phase modulation was appropriately gated in sequential time gates to ensure the long-term stability of automatic polarization compensation in the long-distance quantum key distribution system. Polarization-multiplexed phase modulation was implemented in a protocol quantum key distribution system of 25-km communicating fiber length, generating 20-kHz sifted key rate with a qubit error rate lower than 5%.

DOI
10.1109/lpt.2017.2726115

Related papers

Time-division single-photon Sagnac interferometer for quantum key distribution

Chunyuan Zhou, Heping Zeng

We introduce a single-photon Sagnac interferometer for quantum cryptography using time-division phase modulation. The interferometer was arranged to allow coherent laser pulses to travel clockwise and counter-clockwise along the same fiber loop with the corresponding phases modulated in separated periods, interfering at the exit coupler. High visibility of the single-photon interference was observed over a long-distance Sagnac loop. Stable performance was realized by passive compensation of stress and temperature-dependent drifts of the fiber-optic path. Time-division phase encoding and decoding can be realized by controlling the applied electric pulses on integrated phase modulators in the Sagnac loop, which makes this system suitable for a practical quantum cryptography system.

Applied Physics Letters•Jan 30, 2003•18 citations

Single-photon interference and router-control in a long-distance Sagnac interferometer

Guang Wu, Chunyuan Zhou, Xiuliang Chen +2 more

A novel scheme to realize stable single-photon interference and router-control is demonstrated in this report. Phase difference between clockwise and counter-clockwise single-photons was controlled by time-division phase modulation in an optic fiber Sagnac[1] loop. Due to the annular geometric configuration of the Sagnac loop, clockwise and counter-clockwise single-photons traveled the same optical path and had the same slowly-varied phase drifts, which were automatically compensated. Furthermore, clockwise and counter-clockwise single-photons encounter the same polarization mode dispersion, which was also automatically compensated at the exit port of the Sagnac interferometer.

Frontiers in Optics•Jan 1, 2003•0 citations

Single-photon interference and router-control in an optic fiber Sagnac interferometer

Guang Wu, Chunyuan Zhou, Zeng He-Ping +1 more

A novel scheme to realize stable single-photon interference and router-control is demonstrated in this paper. Phase difference between clockwise and counter-clockwise single-photons is controlled by time-division phase modulation in an optic fiber Sagnac loop. Due to the annular geometric configuration of the Sagnac loop, clockwise and counter-clockwise single-photons travel the same optical path and have the same slowly-varying phase drifts, which are automatically compensated. Furthermore, clockwise and counter-clockwise single-photons encounter the same polarization mode dispersion, which is also automatically compensated at the exit port of the Sagnac interferometer. Long-distance single-mode optic fiber at 1550 nm is used in our experimental realization. Fringe visibility of single-photon interference higher than 98% and fidelity of single-photon router-control higher than 90% have been obtained in a Sagnac fiber loop of 5 km. We also realized a stable single-photon interference in Sagnac fiber loops as long as 27 and 52 km. The corresponding fringe visibilities were higher than 94% and 84%, respectively.

Acta Physica Sinica•Jan 1, 2004•1 citation

Quantum key distribution based on a Sagnac loop interferometer and polarization-insensitive phase modulators

Bing Qi, Leilei Huang, Hoi‐Kwong Lo +1 more

We present a design for a quantum key distribution (QKD) system in a Sagnac loop configuration, employing a novel phase modulation scheme based on frequency shift, and demonstrate stable BB84 QKD operation with high interference visibility and low quantum bit error rate (QBER). The phase modulation is achieved by sending two light pulses with a fixed time delay (or a fixed optical path delay) through a frequency shift element and by modulating the amount of frequency shift. The relative phase between two light pulses upon leaving the frequency-shift element is determined by both the time delay (or the optical path delay) and the frequency shift, and can therefore be controlled by varying the amount of frequency shift. To demonstrate its operation, we used an acousto-optic modulator (AOM) as the frequency-shift element, and vary the driving frequency of the AOM to encode phase information. The interference visibility for a 40 km and a 10 km fiber loop is 96% and 99%, respectively, at single photon level. We ran BB84 protocol in a 40-km Sagnac loop setup continuously for one hour and the measured QBER remained within the 2%-5% range. A further advantage of our scheme is that both phase and amplitude modulation can be achieved simultaneously by frequency and amplitude modulation of the AOM's driving signal, allowing our QKD system the capability of implementing other protocols, such as the decoy-state QKD and the continuous-variable QKD. We also briefly discuss a new type of Eavesdropping strategy ("phase-remapping" attack) in bidirectional QKD system

IEEE International Symposium on Information Theory (ISIT)•Jul 1, 2006•7 citations

Estimating the phase modulator location in Sagnac interferometers for quantum key distribution systems

Konstantin V. Stepanov, A.V. Borisova, A. G. Vtyurina

Subject of study . A phase modulation device for encoding quantum states based on an electro-optical phase modulator asymmetrically located in a Sagnac interferometer is studied. Aim of study. An easily implemented and repeatable method for measuring the path difference to a phase modulator inside a Sagnac interferometer in quantum key distribution systems is developed. Method. A phase difference between the clockwise and counterclockwise continuous propagating light is introduced in the beamsplitter of a Sagnac interferometer when an electrical pulse is transmitted to a phase modulator. Moreover, the asymmetric location of the phase modulator means that this single electrical pulse introduces twice the optical phase difference. Main results. A technique for measuring the difference in propagation time for light traveling in opposite directions to reach the phase modulator in a Sagnac interferometer was proposed and experimentally tested; this technique can be used for simultaneous modulation of phase and intensity in quantum key distribution systems. Practical significance. Our results regarding this highly accurate and easily implementable technique for measuring the difference in propagation time for light traveling in opposite directions to reach the asymmetrically positioned phase modulator in a Sagnac interferometer are relevant for the production of optoelectronic modules used in quantum key distribution systems, where this time difference directly affects the system quality and overall performance.

Journal of Optical Technology•Sep 1, 2025•0 citations

Quantum key distribution based on phase encoding and polarization measurement

Haiqiang Ma, Zhao Jian-Ling, Ling-An Wu

A one-way quantum key distribution scheme based on intrinsically stable Faraday-mirror-type Michelson interferometers with four-port polarizing beam splitters has been demonstrated that can compensate for birefringence effects automatically. The encoding is performed with phase modulators, but decoding is accomplished through measurement of the polarization state of Bob's photons. An extinction ratio of about 30 dB was maintained for several hours over 50 km of fiber at 1310 nm without any adjustment to the setup, which shows its good potential for practical systems.

arXiv:quant-ph/0702086•Optics Letters•Feb 15, 2007•18 citations
Polarization-multiplexed phase modulation was demonstrated in a Sagnac interferometer for polarization-auto-compensating quantum key distribution. The Sagnac interferometer was composed of a polarization beam splitter to split the signal pulses into clockwise and counter-clockwise beams of different polarizations, a Faraday rotator to rotate the polarizations of the split clockwise and counter-clockwise beams, and two phase-modulators asymmetrically set in the Sagnac ring. With this structure, the delays of the electronic triggering signals for the two phase-modulators could be set separately, reducing the difficulty in the setup and achieving more precise phase modulation on different polarized beams. Such polarization-multiplexed phase modulation was appropriately gated in sequential time gates to ensure the long-term stability of automatic polarization compensation in the long-distance quantum key distribution system. Polarization-multiplexed phase modulation was implemented in a protocol quantum key distribution system of 25-km communicating fiber length, generating 20-kHz sifted key rate with a qubit error rate lower than 5%.
We introduce a single-photon Sagnac interferometer for quantum cryptography using time-division phase modulation. The interferometer was arranged to allow coherent laser pulses to travel clockwise and counter-clockwise along the same fiber loop with the corresponding phases modulated in separated periods, interfering at the exit coupler. High visibility of the single-photon interference was observed over a long-distance Sagnac loop. Stable performance was realized by passive compensation of stress and temperature-dependent drifts of the fiber-optic path. Time-division phase encoding and decoding can be realized by controlling the applied electric pulses on integrated phase modulators in the Sagnac loop, which makes this system suitable for a practical quantum cryptography system.
A novel scheme to realize stable single-photon interference and router-control is demonstrated in this report. Phase difference between clockwise and counter-clockwise single-photons was controlled by time-division phase modulation in an optic fiber Sagnac[1] loop. Due to the annular geometric configuration of the Sagnac loop, clockwise and counter-clockwise single-photons traveled the same optical path and had the same slowly-varied phase drifts, which were automatically compensated. Furthermore, clockwise and counter-clockwise single-photons encounter the same polarization mode dispersion, which was also automatically compensated at the exit port of the Sagnac interferometer.
A novel scheme to realize stable single-photon interference and router-control is demonstrated in this paper. Phase difference between clockwise and counter-clockwise single-photons is controlled by time-division phase modulation in an optic fiber Sagnac loop. Due to the annular geometric configuration of the Sagnac loop, clockwise and counter-clockwise single-photons travel the same optical path and have the same slowly-varying phase drifts, which are automatically compensated. Furthermore, clockwise and counter-clockwise single-photons encounter the same polarization mode dispersion, which is also automatically compensated at the exit port of the Sagnac interferometer. Long-distance single-mode optic fiber at 1550 nm is used in our experimental realization. Fringe visibility of single-photon interference higher than 98% and fidelity of single-photon router-control higher than 90% have been obtained in a Sagnac fiber loop of 5 km. We also realized a stable single-photon interference in Sagnac fiber loops as long as 27 and 52 km. The corresponding fringe visibilities were higher than 94% and 84%, respectively.
We present a design for a quantum key distribution (QKD) system in a Sagnac loop configuration, employing a novel phase modulation scheme based on frequency shift, and demonstrate stable BB84 QKD operation with high interference visibility and low quantum bit error rate (QBER). The phase modulation is achieved by sending two light pulses with a fixed time delay (or a fixed optical path delay) through a frequency shift element and by modulating the amount of frequency shift. The relative phase between two light pulses upon leaving the frequency-shift element is determined by both the time delay (or the optical path delay) and the frequency shift, and can therefore be controlled by varying the amount of frequency shift. To demonstrate its operation, we used an acousto-optic modulator (AOM) as the frequency-shift element, and vary the driving frequency of the AOM to encode phase information. The interference visibility for a 40 km and a 10 km fiber loop is 96% and 99%, respectively, at single photon level. We ran BB84 protocol in a 40-km Sagnac loop setup continuously for one hour and the measured QBER remained within the 2%-5% range. A further advantage of our scheme is that both phase and amplitude modulation can be achieved simultaneously by frequency and amplitude modulation of the AOM's driving signal, allowing our QKD system the capability of implementing other protocols, such as the decoy-state QKD and the continuous-variable QKD. We also briefly discuss a new type of Eavesdropping strategy ("phase-remapping" attack) in bidirectional QKD system
Subject of study . A phase modulation device for encoding quantum states based on an electro-optical phase modulator asymmetrically located in a Sagnac interferometer is studied. Aim of study. An easily implemented and repeatable method for measuring the path difference to a phase modulator inside a Sagnac interferometer in quantum key distribution systems is developed. Method. A phase difference between the clockwise and counterclockwise continuous propagating light is introduced in the beamsplitter of a Sagnac interferometer when an electrical pulse is transmitted to a phase modulator. Moreover, the asymmetric location of the phase modulator means that this single electrical pulse introduces twice the optical phase difference. Main results. A technique for measuring the difference in propagation time for light traveling in opposite directions to reach the phase modulator in a Sagnac interferometer was proposed and experimentally tested; this technique can be used for simultaneous modulation of phase and intensity in quantum key distribution systems. Practical significance. Our results regarding this highly accurate and easily implementable technique for measuring the difference in propagation time for light traveling in opposite directions to reach the asymmetrically positioned phase modulator in a Sagnac interferometer are relevant for the production of optoelectronic modules used in quantum key distribution systems, where this time difference directly affects the system quality and overall performance.
A one-way quantum key distribution scheme based on intrinsically stable Faraday-mirror-type Michelson interferometers with four-port polarizing beam splitters has been demonstrated that can compensate for birefringence effects automatically. The encoding is performed with phase modulators, but decoding is accomplished through measurement of the polarization state of Bob's photons. An extinction ratio of about 30 dB was maintained for several hours over 50 km of fiber at 1310 nm without any adjustment to the setup, which shows its good potential for practical systems.