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:2203.00012 · Nature Communications

Quantum capacities of transducers

Chiao-Hsuan Wang, Fangxin Li, Liang Jiang

Published Nov 5, 2022• 23 citations
arXivHTMLPDF

Abstract

High-performance quantum transducers, which faithfully convert quantum information between disparate physical carriers, are essential in quantum science and technology. Different figures of merit, including efficiency, bandwidth, and added noise, are typically used to characterize the transducers' ability to transfer quantum information. Here we utilize quantum capacity, the highest achievable qubit communication rate through a channel, to define a single metric that unifies various criteria of a desirable transducer. Using the continuous-time quantum capacities of bosonic pure-loss channels as benchmarks, we investigate the optimal designs of generic quantum transduction schemes implemented by transmitting external signals through a coupled bosonic chain. With physical constraints on the maximal coupling rate [Formula: see text], the highest continuous-time quantum capacity [Formula: see text] is achieved by transducers with a maximally flat conversion frequency response, analogous to Butterworth electric filters. We further investigate the effect of thermal noise on the performance of transducers.

DOI
10.1038/s41467-022-34373-8

Related papers

Figures of merit for quantum transducers

Emil Zeuthen, Albert Schließer, Anders Søndberg Sørensen +1 more

Abstract Recent technical advances have sparked renewed interest in physical systems that couple simultaneously to different parts of the electromagnetic spectrum, thus enabling transduction of signals between vastly different frequencies at the level of single quanta. Such hybrid systems have demonstrated frequency conversion of classical signals and have the potential of enabling quantum state transfer, e.g., between superconducting circuits and traveling optical signals. This article describes a simple approach for the theoretical characterization of the performance of quantum transducers. Given that, in practice, one cannot attain ideal one-to-one quantum conversion, we explore how imperfections impact the performance of the transducer in various scenarios. We quantify how knowledge of the well-established transducer parameters signal transfer efficiency η and added noise N suffices to assess its performance in a variety of transduction schemes ranging from classical signal detection to applications for quantum information processing.

arXiv:1610.01099•Quantum Science and Technology•Apr 15, 2020•49 citations

High-throughput bidirectional electro-optic transduction assessed with a practical quantum capacity

Maxwell D. Urmey, S. Dickson, Kazemi Adachi +7 more

A microwave-optical transducer of sufficiently low noise and high signal transfer rate would allow entanglement to be distributed between superconducting quantum processors reliably within the lifetimes of their quantum memories. We report the continuous operation of an efficient transducer at high enough bandwidth to realize kHz signal transfer rates, in downconversion as well as upconversion, with noise levels approaching that required for quantum information transfer. To define the significance of our advance and clarify the multifaceted performance required for quantum networking tasks, we derive a broadband quantum channel capacity that bounds the maximum rate at which quantum information can be sent through realistic finite-bandwidth thermal-loss channels. This capacity serves as a comprehensive measure of transducer capability and provides insight into the relative importance of disparate performance metrics. We find that the broadband capacity depends on the throughput---defined as the product of efficiency, bandwidth, and duty cycle---and on the added noise. We present measurements of a membrane-based opto-electromechanical transducer with high throughput of 7 kHz and at an input-referred added noise of 3 photons in both upconversion and downconversion, demonstrating that bidirectional transducer capacities comparable to superconducting qubit decay rates are within reach. In downconversion, throughput of this magnitude at the few-photon noise level is unprecedented, marking an improvement of nearly four orders of magnitude over previous work.

arXiv:2507.09873•Jul 14, 2025•0 citations

Optimized Protocols for Duplex Quantum Transduction

Zhaoyou Wang, Mengzhen Zhang, Yat Wong +2 more

Quantum transducers convert quantum signals through hybrid interfaces of physical platforms in quantum networks. Modeled as quantum communication channels, performance of unidirectional quantum transduction can be measured by the quantum channel capacity. However, characterizing performance of quantum transducers used for duplex quantum transduction where signals are converted bidirectionally remains an open question. Here, we propose rate regions to characterize the performance of duplex quantum transduction. Using this tool, we find that quantum transducers optimized for simultaneous duplex transduction can outperform strategies based on the standard protocol of time-shared unidirectional transduction. Integrated over the frequency domain, we demonstrate that the rate region can also characterize quantum transducers with finite bandwidth.

arXiv:2305.15648•Physical Review Letters•Nov 30, 2023•3 citations

Intraband entanglement–assisted cavity electro-optic quantum transducer

Yu-Bo Hou, Rui-Zhe You, Di-Jia Zhang +2 more

Quantum transduction is a key technology for connecting different quantum technologies across varied frequencies. However, it remains a major challenge to overcome the high threshold for achieving positive capacity of traditional quantum transduction channels. Recently, an entanglement-assisted transducer was proposed based on a cavity-optic system [Opt. Quantum 2, 475 (2024)], where a modified bosonic loss channel was obtained, and the transduction efficiency can be enhanced by properly tuning the squeezing parameters. In this paper, we further identify three types of quantum channels enabled by this design, offering additional options for implementing the proposed transduction schemes. Compared to the transducers without entanglement assistance, the scheme also shows a great enhancement in the conversion bandwidth for achieving high quantum capacity, further increasing its value in practical applications.

arXiv:2503.20305•Physical Review Applied•Dec 10, 2025•0 citations

High-Performance Quantum Transduction with Correlated Noise

Yu-Bo Hou, Xiaoan Ai, Pengbo Li +1 more

Quantum transduction, which coherently converts quantum states between microwave and optical frequency domains, is a key technology for hybrid quantum architectures. Its performance, however, is fundamentally limited by thermal noise. Direct quantum transduction is particularly susceptible to noise and often fails to achieve positive quantum capacity. Entanglement-based quantum transduction, which realizes state conversion through quantum teleportation assisted by microwave-optical entanglement, is intrinsically more robust against thermal noise. However, generating sufficiently strong entanglement in a realistic thermal environment remains a major challenge. In this paper, we exploit correlated noise as a resource for quantum transduction. For direct quantum transduction, it is shown that the noise correlations give rise to controllable interference terms that substantially suppress the effective channel noise. For entanglement-based quantum transduction, the same correlations enhance the generation of microwave-optical entanglement, thereby improving the fidelity of teleportation-based conversion. As a result, both transduction protocols exhibit broad regions of positive quantum capacity over experimentally relevant ranges of cooperativity. We further discuss a possible physical mechanism for engineering the required noise correlations, providing theoretical guidance for experimental implementations. These results suggest that correlated noise can substantially relax the stringent cryogenic requirements for microwave-optical quantum transduction and facilitate the realization of practical hybrid quantum networks.

quant-pharXiv:2608.06683•Aug 10, 2026•0 citations

Quantum communication over bandwidth-and-time-limited channels

Aditya Gandotra, Zhaoyou Wang, Aashish A. Clerk +1 more

Standard communication systems have transmission spectra that characterize their ability to perform frequency multiplexing over a finite bandwidth. Realistic quantum signals in quantum communication systems like transducers are inherently limited in time due to intrinsic decoherence and finite latency, which hinders the direct implementation of frequency-multiplexed encoding. We investigate quantum channel capacities for bandwidth-and-time-limited (BTL) channels to establish the optimal communication strategy in a realistic setting. For pure-loss bosonic channels, we derive analytical solutions of the optimal encoding and decoding modes for Lorentzian and box transmission spectra, along with numerical solutions for various other transmissions. Our findings reveal a general feature of sequential activation of quantum channels as the input signal duration increases, as well as the existence of optimal signal length for scenarios where only a limited number of channels are in use.

arXiv:2502.08831•Physical Review A•Feb 23, 2026•1 citation
High-performance quantum transducers, which faithfully convert quantum information between disparate physical carriers, are essential in quantum science and technology. Different figures of merit, including efficiency, bandwidth, and added noise, are typically used to characterize the transducers' ability to transfer quantum information. Here we utilize quantum capacity, the highest achievable qubit communication rate through a channel, to define a single metric that unifies various criteria of a desirable transducer. Using the continuous-time quantum capacities of bosonic pure-loss channels as benchmarks, we investigate the optimal designs of generic quantum transduction schemes implemented by transmitting external signals through a coupled bosonic chain. With physical constraints on the maximal coupling rate [Formula: see text], the highest continuous-time quantum capacity [Formula: see text] is achieved by transducers with a maximally flat conversion frequency response, analogous to Butterworth electric filters. We further investigate the effect of thermal noise on the performance of transducers.
Abstract Recent technical advances have sparked renewed interest in physical systems that couple simultaneously to different parts of the electromagnetic spectrum, thus enabling transduction of signals between vastly different frequencies at the level of single quanta. Such hybrid systems have demonstrated frequency conversion of classical signals and have the potential of enabling quantum state transfer, e.g., between superconducting circuits and traveling optical signals. This article describes a simple approach for the theoretical characterization of the performance of quantum transducers. Given that, in practice, one cannot attain ideal one-to-one quantum conversion, we explore how imperfections impact the performance of the transducer in various scenarios. We quantify how knowledge of the well-established transducer parameters signal transfer efficiency η and added noise N suffices to assess its performance in a variety of transduction schemes ranging from classical signal detection to applications for quantum information processing.
A microwave-optical transducer of sufficiently low noise and high signal transfer rate would allow entanglement to be distributed between superconducting quantum processors reliably within the lifetimes of their quantum memories. We report the continuous operation of an efficient transducer at high enough bandwidth to realize kHz signal transfer rates, in downconversion as well as upconversion, with noise levels approaching that required for quantum information transfer. To define the significance of our advance and clarify the multifaceted performance required for quantum networking tasks, we derive a broadband quantum channel capacity that bounds the maximum rate at which quantum information can be sent through realistic finite-bandwidth thermal-loss channels. This capacity serves as a comprehensive measure of transducer capability and provides insight into the relative importance of disparate performance metrics. We find that the broadband capacity depends on the throughput---defined as the product of efficiency, bandwidth, and duty cycle---and on the added noise. We present measurements of a membrane-based opto-electromechanical transducer with high throughput of 7 kHz and at an input-referred added noise of 3 photons in both upconversion and downconversion, demonstrating that bidirectional transducer capacities comparable to superconducting qubit decay rates are within reach. In downconversion, throughput of this magnitude at the few-photon noise level is unprecedented, marking an improvement of nearly four orders of magnitude over previous work.
Quantum transducers convert quantum signals through hybrid interfaces of physical platforms in quantum networks. Modeled as quantum communication channels, performance of unidirectional quantum transduction can be measured by the quantum channel capacity. However, characterizing performance of quantum transducers used for duplex quantum transduction where signals are converted bidirectionally remains an open question. Here, we propose rate regions to characterize the performance of duplex quantum transduction. Using this tool, we find that quantum transducers optimized for simultaneous duplex transduction can outperform strategies based on the standard protocol of time-shared unidirectional transduction. Integrated over the frequency domain, we demonstrate that the rate region can also characterize quantum transducers with finite bandwidth.
Quantum transduction is a key technology for connecting different quantum technologies across varied frequencies. However, it remains a major challenge to overcome the high threshold for achieving positive capacity of traditional quantum transduction channels. Recently, an entanglement-assisted transducer was proposed based on a cavity-optic system [Opt. Quantum 2, 475 (2024)], where a modified bosonic loss channel was obtained, and the transduction efficiency can be enhanced by properly tuning the squeezing parameters. In this paper, we further identify three types of quantum channels enabled by this design, offering additional options for implementing the proposed transduction schemes. Compared to the transducers without entanglement assistance, the scheme also shows a great enhancement in the conversion bandwidth for achieving high quantum capacity, further increasing its value in practical applications.
Quantum transduction, which coherently converts quantum states between microwave and optical frequency domains, is a key technology for hybrid quantum architectures. Its performance, however, is fundamentally limited by thermal noise. Direct quantum transduction is particularly susceptible to noise and often fails to achieve positive quantum capacity. Entanglement-based quantum transduction, which realizes state conversion through quantum teleportation assisted by microwave-optical entanglement, is intrinsically more robust against thermal noise. However, generating sufficiently strong entanglement in a realistic thermal environment remains a major challenge. In this paper, we exploit correlated noise as a resource for quantum transduction. For direct quantum transduction, it is shown that the noise correlations give rise to controllable interference terms that substantially suppress the effective channel noise. For entanglement-based quantum transduction, the same correlations enhance the generation of microwave-optical entanglement, thereby improving the fidelity of teleportation-based conversion. As a result, both transduction protocols exhibit broad regions of positive quantum capacity over experimentally relevant ranges of cooperativity. We further discuss a possible physical mechanism for engineering the required noise correlations, providing theoretical guidance for experimental implementations. These results suggest that correlated noise can substantially relax the stringent cryogenic requirements for microwave-optical quantum transduction and facilitate the realization of practical hybrid quantum networks.
Standard communication systems have transmission spectra that characterize their ability to perform frequency multiplexing over a finite bandwidth. Realistic quantum signals in quantum communication systems like transducers are inherently limited in time due to intrinsic decoherence and finite latency, which hinders the direct implementation of frequency-multiplexed encoding. We investigate quantum channel capacities for bandwidth-and-time-limited (BTL) channels to establish the optimal communication strategy in a realistic setting. For pure-loss bosonic channels, we derive analytical solutions of the optimal encoding and decoding modes for Lorentzian and box transmission spectra, along with numerical solutions for various other transmissions. Our findings reveal a general feature of sequential activation of quantum channels as the input signal duration increases, as well as the existence of optimal signal length for scenarios where only a limited number of channels are in use.