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

Advanced Photonics Research

Security‐Enhanced Differential Binary‐Phase‐Shift‐Keying Quantum Key Distribution With a Wavelength‐Switchable Single‐Photon Carrier

Sze‐En Lai, Chih‐Hsien Cheng, Atsushi Matsumoto, Kouichi Akahane, Gong‐Ru Lin

Published Jun 1, 2026• 1 citation
Publisher

Abstract

A single‐chip dual‐wavelength coherent photon source is proposed to introduce additional parametric uncertainty and improve the security scaling of single‐photon differential binary‐phase‐shift‐keying quantum key distribution (D‐BPSK‐QKD). Simultaneous lasing of two longitudinal modes in the same semiconductor laser cavity generates two coherent photon groups at different wavelengths, and attenuation of their combined output to the single‐photon level inevitably produces wavelength uncertainty at the receiver. Optical injection control enables stabilized D‐BPSK encoding on one selected mode while the other mode remains free‐running, which supports mode‐selective coding and a decoy scenario during single‐photon streaming. This intermodal wavelength switching/selection provides another degree of freedom for QKD security and increases the difficulty of eavesdropping attacks. The dual‐wavelength single‐photon bits deliver D‐BPSK‐QKD codes with a QBER of <4.1% under 2 10 ‐bit encryption, a sifted key rate of 408.6 kbit/s, and a secure key rate (SKR) of 10.5 kbit/s at an average photon number of 0.22 photons#/bit. The transmission distance can be extended to more than 13.25 km with a SKR of 3.6 kbit/s under a nearly equivalent QBER. This versatile wavelength‐uncertain coding or decoying operation enables flexible and secure D‐BPSK‐QKD transmission over wavelength‐division‐multiplexed channelized single‐mode fiber links.

DOI
10.1002/adpr.202500327

Related papers

All-Optical Control of Wavelength-Shifted Serrodyne DPSK Quantum Key Distributor

Yuanjie Yang, Shih-Chang Hsu, Gong‐Ru Lin

All-optical controlled wavelength-switchable single-photon frequency serrodyne carrier based on the master-control-slave injection scheme is performed to switch the slave laser diode between single and dual lasing modes for time-division-multiplexing the carrier-frequency-serrodyne differential-phase-shift quantum key distribution.

OptoElectronics and Communications Conference and International Conference on Photonics in Switching and Computing (OECC/PSC)•Jun 29, 2025•0 citations

A Fully‐Connected Chip‐Integrated Reconfigurable Mode‐Pairing Quantum Key Distribution Network

Xiao-Lei Jiang, Wei Gao, Yan‐Yang Zhou +12 more

ABSTRACT Quantum key distribution (QKD) provides an information‐theoretic security framework for building QKD networks (QNs). However, existing QN architectures face critical challenges: trusted‐node‐based designs inherently expose relay nodes to physical compromise, while entanglement‐based approaches suffer from high implementation costs of sources. Here, this work proposes and conceptually validates a fully‐connected chip‐integrated reconfigurable QN based on the mode‐pairing (MP) QKD protocol. By combining hybrid‐integrated external‐cavity laser (ECL) chips with wavelength selective switch (WSS) chips, this architecture enables simultaneous secure key sharing among arbitrary users using only two wavelengths through a wavelength‐path dynamic resource allocation mechanism. Compared to conventional QN architectures, this approach significantly reduces the required port count and wavelength resources while supporting flexible reconfiguration such as on‐demand secure key supplementation and rapid reconstruction of faulty links‐capabilities unattainable in existing schemes. Experimental results demonstrate that the system achieves an average finite‐size secret key rate (SKR) of 5.72 kbps for each user pair under a channel loss of 40 dB. The compact design, cost‐effectiveness, and scalability of this architecture establish a robust foundation for the deployment of practical QNs.

Laser & Photonics Review•Aug 1, 2026•1 citation

Experimental Demonstration of Coexistence of Classical and Quantum Communication in Quantum Key Distribution Link

Gokul Agasthilingam, Harinee Natarajan, Varun Raghunathan

This paper presents a quantum key distribution (QKD) system that combines classical and quantum signals in a single optical channel for quantum key distribution application. We carefully optimize the communication link by placing the bright classical channel wavelength longer than the weak quantum one, number and specification of wavelength division multiplexers, and maximizing on-off extinction in the intensity modulator to minimize crosstalk of bright classical photons onto the quantum channel. Our experiments demonstrate a secret key rate (SKR) of 4.39 kbps for an emulated channel length of 65.5 km with less than 3% quantum bit error rate (QBER). The experimental study discussed here is relevant for utilization of existing optical fiber networks for QKD, making the system more robust for practical usage.

IEEE Microwaves, Antennas, and Propagation Conference (MAPCON)•Dec 11, 2023•2 citations

Wavelength-Switching in Single-Mode Injection-Locked Dual-Mode DFBLD Enables Phase Shift Keying for QKD

Szu-En Lai, Chih‐Hsien Cheng, Yu-Sheng Liao +2 more

Wavelength selective injection-locking of a 1545.59-/1548.18-nm dual-mode DFBLD with a transient-current-switched single-mode master DFBLD is performed for differential phase-shift-keying and delay-interferometric on-off-keying at 192 MHz that enables secure and complex quantum-key-distribution via alternative wavelength switching.

•Jan 1, 2023•0 citations

O-band single-photon quantum key distributor master-to-slave injection-locked DFBLD pair

Cheng-Lin Tsou, Chih‐Hsien Cheng, Atsushi Matsumoto +2 more

In comparison with the rapidly developing progress on the optical C-band (1525-1565 nm) master-to-slave injection-locked transmitter to perform the coherent single-photon quantum key distribution (QKD), the development on the O-band (1250-1350 nm) QKD transmitter is somewhat delayed as the commercially available wavelength-matched narrow-linewidth distributed feedback laser diode (DFBLD) pair is hardly accessible up to now. By using the DFBLDs with only sub-MHz linewidth and relatively deviated wavelength for the first time, this work demonstrates the optically differential-phase-shift-keying (DPS) QKD by an O-band master-to-slave injection-locked DFBLD pair. The master and slave DFBLDs with wavelength fluctuations of ±0.05% and ±0.2 pm are controlled by a thermo-electric cooler with a feedback gain of 100. The 1-bit delay interferometer (DI) under thermo-insulation maintains its visibility at >96% with dP o /P o and dP o /dt measured below ±0.1% and ±1 × 10 −3 mW/s. By RZ-OOK modulating the master DFBLD with step-like power coding at 150 µW to induce π phase shift in the injection-locked slave DFBLD, the rising-/falling-edge DPS envelope distortion of the slave DFBLD diminishes by decreasing the bias current of the master DFBLD from 7I th (35 mA) to 2I th (10 mA). This phenomenon enables the 128-bit DPS-QKD transmission with a quantum bit-error rate (QBER) of 3.57% and a secure key rate of 3.524 kbit/s in the 6-km SMF link. The O-band injection-locked single-photon DPS-QKD bit-stream with a mean photon number of 0.2 #/bit minimizes its decoding QBER to 3.88% and 4.84% for 512-bit and 1024-bit, respectively.

Optics Continuum•Apr 8, 2024•0 citations

A Reconfigurable Silicon Photonic Chip for Dual-Degree-of-Freedom Quantum Key Distribution

Xu Yan, Xin Hua, Yanxin Han +8 more

We present the first demonstration of a novel silicon photonic encoder chip for QKD that enables on-demand selection of the encoding degree of freedom—either polarization or time-bin phase—for quantum state generation. When deployed in a QKD system, we achieve secure key rates of 1 kbps over 128 km using polarization encoding and 2.4 kbps over 75 km using time-bin phase encoding through single-mode fiber.

Optical Fiber Communication Conference•Jan 1, 2026•0 citations
A single‐chip dual‐wavelength coherent photon source is proposed to introduce additional parametric uncertainty and improve the security scaling of single‐photon differential binary‐phase‐shift‐keying quantum key distribution (D‐BPSK‐QKD). Simultaneous lasing of two longitudinal modes in the same semiconductor laser cavity generates two coherent photon groups at different wavelengths, and attenuation of their combined output to the single‐photon level inevitably produces wavelength uncertainty at the receiver. Optical injection control enables stabilized D‐BPSK encoding on one selected mode while the other mode remains free‐running, which supports mode‐selective coding and a decoy scenario during single‐photon streaming. This intermodal wavelength switching/selection provides another degree of freedom for QKD security and increases the difficulty of eavesdropping attacks. The dual‐wavelength single‐photon bits deliver D‐BPSK‐QKD codes with a QBER of <4.1% under 2 10 ‐bit encryption, a sifted key rate of 408.6 kbit/s, and a secure key rate (SKR) of 10.5 kbit/s at an average photon number of 0.22 photons#/bit. The transmission distance can be extended to more than 13.25 km with a SKR of 3.6 kbit/s under a nearly equivalent QBER. This versatile wavelength‐uncertain coding or decoying operation enables flexible and secure D‐BPSK‐QKD transmission over wavelength‐division‐multiplexed channelized single‐mode fiber links.
ABSTRACT Quantum key distribution (QKD) provides an information‐theoretic security framework for building QKD networks (QNs). However, existing QN architectures face critical challenges: trusted‐node‐based designs inherently expose relay nodes to physical compromise, while entanglement‐based approaches suffer from high implementation costs of sources. Here, this work proposes and conceptually validates a fully‐connected chip‐integrated reconfigurable QN based on the mode‐pairing (MP) QKD protocol. By combining hybrid‐integrated external‐cavity laser (ECL) chips with wavelength selective switch (WSS) chips, this architecture enables simultaneous secure key sharing among arbitrary users using only two wavelengths through a wavelength‐path dynamic resource allocation mechanism. Compared to conventional QN architectures, this approach significantly reduces the required port count and wavelength resources while supporting flexible reconfiguration such as on‐demand secure key supplementation and rapid reconstruction of faulty links‐capabilities unattainable in existing schemes. Experimental results demonstrate that the system achieves an average finite‐size secret key rate (SKR) of 5.72 kbps for each user pair under a channel loss of 40 dB. The compact design, cost‐effectiveness, and scalability of this architecture establish a robust foundation for the deployment of practical QNs.
This paper presents a quantum key distribution (QKD) system that combines classical and quantum signals in a single optical channel for quantum key distribution application. We carefully optimize the communication link by placing the bright classical channel wavelength longer than the weak quantum one, number and specification of wavelength division multiplexers, and maximizing on-off extinction in the intensity modulator to minimize crosstalk of bright classical photons onto the quantum channel. Our experiments demonstrate a secret key rate (SKR) of 4.39 kbps for an emulated channel length of 65.5 km with less than 3% quantum bit error rate (QBER). The experimental study discussed here is relevant for utilization of existing optical fiber networks for QKD, making the system more robust for practical usage.
In comparison with the rapidly developing progress on the optical C-band (1525-1565 nm) master-to-slave injection-locked transmitter to perform the coherent single-photon quantum key distribution (QKD), the development on the O-band (1250-1350 nm) QKD transmitter is somewhat delayed as the commercially available wavelength-matched narrow-linewidth distributed feedback laser diode (DFBLD) pair is hardly accessible up to now. By using the DFBLDs with only sub-MHz linewidth and relatively deviated wavelength for the first time, this work demonstrates the optically differential-phase-shift-keying (DPS) QKD by an O-band master-to-slave injection-locked DFBLD pair. The master and slave DFBLDs with wavelength fluctuations of ±0.05% and ±0.2 pm are controlled by a thermo-electric cooler with a feedback gain of 100. The 1-bit delay interferometer (DI) under thermo-insulation maintains its visibility at >96% with dP o /P o and dP o /dt measured below ±0.1% and ±1 × 10 −3 mW/s. By RZ-OOK modulating the master DFBLD with step-like power coding at 150 µW to induce π phase shift in the injection-locked slave DFBLD, the rising-/falling-edge DPS envelope distortion of the slave DFBLD diminishes by decreasing the bias current of the master DFBLD from 7I th (35 mA) to 2I th (10 mA). This phenomenon enables the 128-bit DPS-QKD transmission with a quantum bit-error rate (QBER) of 3.57% and a secure key rate of 3.524 kbit/s in the 6-km SMF link. The O-band injection-locked single-photon DPS-QKD bit-stream with a mean photon number of 0.2 #/bit minimizes its decoding QBER to 3.88% and 4.84% for 512-bit and 1024-bit, respectively.