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

Chinese Physics B

Encoding converters for quantum communication networks

Huaxing Xu, Shaohua Wang, Yaqi Song, Ping Zhang, Chang-Lei Wang

Published Apr 17, 2025• 1 citation
Publisher

Abstract

Abstract Quantum communication networks, such as quantum key distribution (QKD) networks, typically employ the measurement-resend mechanism between two users using quantum communication devices based on different quantum encoding types. To achieve direct communication between the devices with different quantum encoding types, in this paper, we propose encoding conversion schemes between the polarization bases (rectilinear, diagonal and circular bases) and the time-bin phase bases (two phase bases and time-bin basis) and design the quantum encoding converters. The theoretical analysis of the encoding conversion schemes is given in detail, and the basis correspondence of encoding conversion and the property of bit flip are revealed. The conversion relationship between polarization bases and time-bin phase bases can be easily selected by controlling a phase shifter. Since no optical switches are used in our scheme, the converter can be operated with high speed. The converters can also be modularized, which may be utilized to realize miniaturization in the future.

DOI
10.1088/1674-1056/adcdeb

Related papers

Photonic qubit encoding interconversion for heterogeneous quantum networking

Vedansh Nehra, Richard J. Birrittella, Christopher C. Tison +10 more

Quantum information processing, communication, and sensing networks are being developed with various qubit platforms that use different encoding schemes. Connecting quantum network nodes to distribute entanglement requires matching photon qubit basis encoding. In this work, we implement an interconversion protocol which converts photon qubit encoding from the polarization basis to the time-bin basis, transmits the photons through a transport fiber with large fluctuations in polarization, and converts back to polarization encoding for ease of measurement. This interconversion scheme faithfully transmits a polarization Bell state across the transport fiber by converting sources of infidelity to changes in transmission rate. These results illustrate a practical approach for interfacing distinct qubit platforms to enable modular and flexible operation in heterogeneous quantum networks.

quant-pharXiv:2604.02081•Physical Review A•Apr 3, 2026•0 citations

Time-bin-to-polarization conversion of ultrafast photonic qubits

Connor Kupchak, Philip J. Bustard, Khabat Heshami +4 more

The encoding of quantum information in photonic time-bin qubits is apt for long-distance quantum communication schemes. In practice, due to technical constraints such as detector response time, or the speed with which copolarized time-bins can be switched, other encodings, e.g., polarization, are often preferred for operations like state detection. Here, we present the conversion of qubits between polarization and time-bin encodings by using a method that is based on an ultrafast optical Kerr shutter and attain efficiencies of 97% and an average fidelity of $0.827\ifmmode\pm\else\textpm\fi{}0.003$ with shutter speeds near 1 ps. Our demonstration delineates an essential requirement for the development of hybrid and high-rate optical quantum networks.

arXiv:1708.07145•Physical Review A•Nov 6, 2017•34 citations

Time-bin phase-encoding quantum key distribution using Sagnac-based optics and compatible electronics

yan-lin tang, Chun Zhou, Dongdong Li +18 more

In this work, we present a new time-bin phase-encoding quantum key distribution (QKD), where the transmitter utilizes an inherently stable Sagnac-type interferometer, and has comparable electrical requirements to existing polarization or phase encoding schemes. This approach does not require intensity calibration and is insensitive to environmental disturbances, making it both flexible and high-performing. We conducted experiments with a compact QKD system to demonstrate the stability and secure key rate performance of the presented scheme. The results show a typical secure key rate of 6.2 kbps@20 dB and 0.4 kbps@30 dB with channel loss emulated by variable optical attenuators. A continuous test of 120-km fiber spool shows a stable quantum bit error rate of the time-bin basis within 0.4%∼0.6% over a consecutive 9-day period without any adjustment. This intrinsically stable and compatible scheme of time-bin phase encoding is extensively applicable in various QKD experiments, including BB84 and measurement-device-independent QKD.

Optics Express•Jul 5, 2023•24 citations

Multiuser quantum communication network via time-bin-entanglement-based frequency conversion and Bell-state measurement

Zhantong Qi, Yang Yilin, Chennan Wu +7 more

Large-scale quantum communication systems often require different channels to be connected to multiple networks via frequency conversion, which requires frequency converters to act as relay points for system connectivity. We propose a quantum network for single-photon frequency conversion based on time-bin entanglement, where legitimate users can realize the spanning of communication bands between users by independently choosing the target conversion frequency mode. The results show that the converter in the network can be used as a bridge to completely connect the two networks by cascading the quadratic nonlinear process. Meanwhile, the converted quantum entangled states are demonstrated in entanglement measurements and can be used for entanglement swapping. This scheme is expected to be widely used in scenarios where different networks share quantum resources, switching communication channels and effectively connecting different multiplexed spectrum. This concept also provides significant applications in large-scale metropolitan area networks.

Physical Review A•May 12, 2025•3 citations

A polarization quantum key distribution scheme based on phase matching

Gao Feifei, Li Zhihui, Liu Chengji +1 more

Abstract The Quantum Key Distribution protocol can encode a single quantum state and implements an information-theoretically secure key distribution protocol in communication. In the actual QKD experimental system, there are usually two encoding methods which are phase encoding and polarization encoding. Ma et al (Phase-Matching Quantum Key Distribution, Phys. Rev. X., 2018, 83) proposed the phase-matching QKD protocol, which has high transmission and it is an extension of the measurement device independent QKD. This paper successfully gives the polarization scheme of this PM-QKD protocol, the bases in the polarization scheme are arbitrary, and eliminates detector side channel attacks. Furthermore, we give the security analysis and simulation results of the polarization scheme, and compare it with the BB84 protocol. The simulation results show that our protocol is superior to the BB84 protocol in terms of transmission distance under the fixed key rate.

arXiv:2003.00750•Laser Physics•Apr 1, 2020•1 citation

Telecom-compatible polarization-to-time-bin conversion of atom-photon entanglement for heterogeneous quantum networks

Christian Haen, Julian Groß-Funk, Max Bergerhoff +5 more

A key enabling feature of future quantum networks is interoperability between platforms that operate at different wavelengths and with different qubit encodings. We demonstrate an interface that converts atom-photon entanglement from polarization encoding at an atomic wavelength to time-bin encoding in the telecom C-band. Atom-entangled photons at 854 nm are generated from a single $^{40}$Ca$^+$ ion. After quantum frequency conversion to 1550 nm, the photonic polarization qubit is converted into a time-bin qubit using a fiber-based Mach--Zehnder-like encoder. Full quantum tomography of the final state verifies that the process preserves entanglement with 96.3(4.2)% fidelity. Together with the independent work of Ferrari et al. [arXiv:2607.07805 (2026)], this is the first demonstration of polarization-to-time-bin conversion of photons entangled with a single atomic quantum memory. The telecom-compatible interface enables robust qubit transmission over optical fibers and provides a key building block for heterogeneous quantum networking architectures.

quant-pharXiv:2607.29609•Aug 3, 2026•0 citations
Abstract Quantum communication networks, such as quantum key distribution (QKD) networks, typically employ the measurement-resend mechanism between two users using quantum communication devices based on different quantum encoding types. To achieve direct communication between the devices with different quantum encoding types, in this paper, we propose encoding conversion schemes between the polarization bases (rectilinear, diagonal and circular bases) and the time-bin phase bases (two phase bases and time-bin basis) and design the quantum encoding converters. The theoretical analysis of the encoding conversion schemes is given in detail, and the basis correspondence of encoding conversion and the property of bit flip are revealed. The conversion relationship between polarization bases and time-bin phase bases can be easily selected by controlling a phase shifter. Since no optical switches are used in our scheme, the converter can be operated with high speed. The converters can also be modularized, which may be utilized to realize miniaturization in the future.
Quantum information processing, communication, and sensing networks are being developed with various qubit platforms that use different encoding schemes. Connecting quantum network nodes to distribute entanglement requires matching photon qubit basis encoding. In this work, we implement an interconversion protocol which converts photon qubit encoding from the polarization basis to the time-bin basis, transmits the photons through a transport fiber with large fluctuations in polarization, and converts back to polarization encoding for ease of measurement. This interconversion scheme faithfully transmits a polarization Bell state across the transport fiber by converting sources of infidelity to changes in transmission rate. These results illustrate a practical approach for interfacing distinct qubit platforms to enable modular and flexible operation in heterogeneous quantum networks.
The encoding of quantum information in photonic time-bin qubits is apt for long-distance quantum communication schemes. In practice, due to technical constraints such as detector response time, or the speed with which copolarized time-bins can be switched, other encodings, e.g., polarization, are often preferred for operations like state detection. Here, we present the conversion of qubits between polarization and time-bin encodings by using a method that is based on an ultrafast optical Kerr shutter and attain efficiencies of 97% and an average fidelity of $0.827\ifmmode\pm\else\textpm\fi{}0.003$ with shutter speeds near 1 ps. Our demonstration delineates an essential requirement for the development of hybrid and high-rate optical quantum networks.
In this work, we present a new time-bin phase-encoding quantum key distribution (QKD), where the transmitter utilizes an inherently stable Sagnac-type interferometer, and has comparable electrical requirements to existing polarization or phase encoding schemes. This approach does not require intensity calibration and is insensitive to environmental disturbances, making it both flexible and high-performing. We conducted experiments with a compact QKD system to demonstrate the stability and secure key rate performance of the presented scheme. The results show a typical secure key rate of 6.2 kbps@20 dB and 0.4 kbps@30 dB with channel loss emulated by variable optical attenuators. A continuous test of 120-km fiber spool shows a stable quantum bit error rate of the time-bin basis within 0.4%∼0.6% over a consecutive 9-day period without any adjustment. This intrinsically stable and compatible scheme of time-bin phase encoding is extensively applicable in various QKD experiments, including BB84 and measurement-device-independent QKD.
Large-scale quantum communication systems often require different channels to be connected to multiple networks via frequency conversion, which requires frequency converters to act as relay points for system connectivity. We propose a quantum network for single-photon frequency conversion based on time-bin entanglement, where legitimate users can realize the spanning of communication bands between users by independently choosing the target conversion frequency mode. The results show that the converter in the network can be used as a bridge to completely connect the two networks by cascading the quadratic nonlinear process. Meanwhile, the converted quantum entangled states are demonstrated in entanglement measurements and can be used for entanglement swapping. This scheme is expected to be widely used in scenarios where different networks share quantum resources, switching communication channels and effectively connecting different multiplexed spectrum. This concept also provides significant applications in large-scale metropolitan area networks.
Abstract The Quantum Key Distribution protocol can encode a single quantum state and implements an information-theoretically secure key distribution protocol in communication. In the actual QKD experimental system, there are usually two encoding methods which are phase encoding and polarization encoding. Ma et al (Phase-Matching Quantum Key Distribution, Phys. Rev. X., 2018, 83) proposed the phase-matching QKD protocol, which has high transmission and it is an extension of the measurement device independent QKD. This paper successfully gives the polarization scheme of this PM-QKD protocol, the bases in the polarization scheme are arbitrary, and eliminates detector side channel attacks. Furthermore, we give the security analysis and simulation results of the polarization scheme, and compare it with the BB84 protocol. The simulation results show that our protocol is superior to the BB84 protocol in terms of transmission distance under the fixed key rate.
A key enabling feature of future quantum networks is interoperability between platforms that operate at different wavelengths and with different qubit encodings. We demonstrate an interface that converts atom-photon entanglement from polarization encoding at an atomic wavelength to time-bin encoding in the telecom C-band. Atom-entangled photons at 854 nm are generated from a single 40^{40}40Ca+^++ ion. After quantum frequency conversion to 1550 nm, the photonic polarization qubit is converted into a time-bin qubit using a fiber-based Mach--Zehnder-like encoder. Full quantum tomography of the final state verifies that the process preserves entanglement with 96.3(4.2)% fidelity. Together with the independent work of Ferrari et al. [arXiv:2607.07805 (2026)], this is the first demonstration of polarization-to-time-bin conversion of photons entangled with a single atomic quantum memory. The telecom-compatible interface enables robust qubit transmission over optical fibers and provides a key building block for heterogeneous quantum networking architectures.