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arXiv:2505.13790 · Physical Review Research

Correlated noise can be beneficial to quantum transducers

Yu-Bo Hou, Xiaoan Ai, Ren You, Changchun Zhong

Published Aug 6, 2025• 1 citation
arXivHTMLPDF

Abstract

Quantum systems are inherently susceptible to noise—a notorious factor that induces decoherence and limits the performance of quantum applications. To mitigate its detrimental effects, various techniques have been developed, including cryogenic cooling, bath engineering, and quantum error correction. In this Letter, we demonstrate that by exploiting noise correlations in coupled quantum systems, the overall impact of noise can be significantly suppressed. Specifically, in a piezo-optomechanical-based microwave-optical quantum transducer, correlations between the noise affecting the acoustic and electrical modes can lead to substantial noise reduction, thereby enhancing the performance of quantum transduction. This reduction is primarily governed by the phase of the piezomechanical coupling and is also influenced by system parameters such as the coupling ratio and mode cooperativity. Since these parameters simultaneously affect the signal transmissivity, they must be optimized to achieve the transducer’s optimal performance. Our work provides a systematic framework for this optimization, offering a guidance for practical designs.

DOI
10.1103/zq39-wzdb

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Quantum systems are inherently susceptible to noise—a notorious factor that induces decoherence and limits the performance of quantum applications. To mitigate its detrimental effects, various techniques have been developed, including cryogenic cooling, bath engineering, and quantum error correction. In this Letter, we demonstrate that by exploiting noise correlations in coupled quantum systems, the overall impact of noise can be significantly suppressed. Specifically, in a piezo-optomechanical-based microwave-optical quantum transducer, correlations between the noise affecting the acoustic and electrical modes can lead to substantial noise reduction, thereby enhancing the performance of quantum transduction. This reduction is primarily governed by the phase of the piezomechanical coupling and is also influenced by system parameters such as the coupling ratio and mode cooperativity. Since these parameters simultaneously affect the signal transmissivity, they must be optimized to achieve the transducer’s optimal performance. Our work provides a systematic framework for this optimization, offering a guidance for practical designs.
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.
The successes of superconducting quantum circuits at local manipulation of quantum information and photonics technology at long-distance transmission of the same have spurred interest in the development of quantum transducers for efficient, low-noise, and bidirectional frequency conversion of photons between the microwave and optical domains. We propose to realize such functionality through the coupling of electrical, piezoelectric, and optomechanical resonators. The coupling of the mechanical subsystems enables formation of a resonant mechanical supermode that provides a mechanically-mediated, efficient single interface to both the microwave and optical domains. The conversion process is analyzed by applying an equivalent circuit model that relates device-level parameters to overall figures of merit for conversion efficiency η\etaη and added noise NNN. These can be further enhanced by proper impedance matching of the transducer to an input microwave transmission line. The performance of potential transducers is assessed through finite-element simulations, with a focus on geometries in GaAs, followed by considerations of the AlN, LiNbO3_33​, and AlN-on-Si platforms. We present strategies for maximizing η\etaη and minimizing NNN, and find that simultaneously achieving η>50 %\eta>50~\%η>50 % and N<0.5N < 0.5N<0.5 should be possible with current technology. Our comprehensive analysis of the full transduction chain enables us to outline a development path for the realization of high-performance quantum transducers that will constitute a new resource for quantum information science.
Coherent transduction of quantum states from the microwave to the optical domain can play a key role in quantum networking and distributed quantum computing. We present the design of a piezo-optomechanical device formed in a hybrid lithium niobate on silicon platform, that is suitable for microwave-to-optical quantum transduction. Our design is based on acoustic hybridization of an ultra-low mode volume piezoacoustic cavity with an optomechanical crystal cavity. The strong piezoelectric nature of lithium niobate allows us to mediate transduction via an acoustic mode which only minimally interacts with the lithium niobate, and is predominantly silicon-like, with very low electrical and acoustic loss. We estimate that this transducer can realize an intrinsic conversion efficiency of up to 35% with <0.5 added noise quanta when resonantly coupled to a superconducting transmon qubit and operated in pulsed mode at 10 kHz repetition rate. The performance improvement gained in such hybrid lithium niobate-silicon transducers make them suitable for heralded entanglement of qubits between superconducting quantum processors connected by optical fiber links.
A quantum transducer converts an input signal to an output probe at a distant frequency band while maintaining the quantum information with high fidelity, which is crucial for quantum networking and distributed quantum sensing and computing. In terms of microwave–optical quantum transduction, the state-of-the-art quantum transducers suffer low transduction efficiency from weak nonlinear coupling, wherein increasing pump power to enhance efficiency inevitably leads to thermal noise from heating. Moreover, we reveal that the efficiency-bandwidth product of a cavity electro-optical or electro-optomechanical transducer is fundamentally limited by pump power and nonlinear coupling coefficient, irrespective of cavity engineering efforts. To overcome this fundamental limit, we propose to noiselessly boost the transduction efficiency by consuming intraband entanglement (e.g., microwave–microwave or optical–optical entanglement in the case of microwave–optical transduction). Via a squeezer–coupler–antisqueezer sandwich structure, the protocol enhances the transduction efficiency to unity in the ideal lossless case, given an arbitrarily weak pump and nonlinear coupling. In practical cavity systems, our entanglement-assisted protocol surpasses the non-assisted fundamental limit of the efficiency-bandwidth product and reduces the threshold cooperativity for positive quantum capacity by a factor proportional to two-mode squeezing gain. Given a fixed cooperativity, our approach increases the broadband quantum capacity by orders of magnitude. The entanglement-assisted advantage is robust to ancilla loss and cavity detuning.
Optical quantum networks provide a natural route for connecting distant superconducting quantum processors, enabling distributed quantum computation, sensing, and communication. Piezo-optomechanical transducers are among the leading candidates for scalable microwave-to-optical quantum interfaces. However, prior one-dimensional piezo-optomechanical transducers remain limited by optical-absorption-induced heating and the resulting thermal noise. Two-dimensional optomechanical crystals offer substantially improved thermalization from better thermal anchoring, but their structural complexity has so far hindered the realization of a fully integrated two-dimensional transducer. Here, we overcome this challenge with a new design strategy based on band structure engineering. We fabricate the devices and experimentally characterize the response, measuring an electromechanical damping rate of 4.6 kHz at room temperature and electromechanical coupling rate of 0.17 MHz by wire-bonding to a multi-mode microwave resonator at 10 mK. Bidirectional transduction is performed with a calibrated internal efficiency of 0.85\% in the continuous-wave operation, alongside pulsed photon-phonon pair generation near its quantum ground state. Our results represent a significant step toward high-efficiency and low-noise transducers for entangling remote superconducting qubits.
Piezoelectric optomechanical platforms represent one of the most promising routes toward achieving quantum transduction of photons between the microwave and optical frequency domains. However, there are significant challenges to achieving near-unity transduction efficiency. The authors discuss such factors in the context of the two main approaches being pursued for high efficiency transduction. The first approach uses 1D nanobeam optomechanical crystals excited by interdigitated transducers and is characterized by large single-photon optomechanical coupling strength, limited intracavity pump photon population to avoid absorption-induced heating (at cryogenic temperature), and low phonon injection efficiency from the transducer to the optomechanical cavity. The second approach uses (quasi) bulk acoustic wave resonators integrated into photonic Fabry–Perot cavity geometries and is characterized by low single-photon optomechanical coupling strength, high intracavity pump photon population without significant heating, and high phonon injection efficiency. After reviewing the current status of both approaches, the need for co-designing the electromechanical and optomechanical sub-systems is discussed in order to achieve high transduction efficiencies, taking the GaAs piezo-optomechanical platform as an example.