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arXiv:2503.06544 · Advanced Quantum Technologies

Multifunctional Nonreciprocal Quantum Device Based on Superconducting Quantum Circuit

Yue Cai, Jie Liu, Kang‐Jie Ma, Lei Tan

Published Sep 15, 2025• 0 citations
arXivHTMLPDF

Abstract

Abstract Nonreciprocal devices, such as isolator or circulator, are crucial for information routing and processing in quantum networks. Traditional nonreciprocal devices, which rely on the application of bias magnetic fields to break time‐reversal symmetry and Lorentz reciprocity, tend to be bulky and require strong static magnetic fields. This makes them challenging to implement in highly integrated large‐scale quantum networks. Therefore, a multifunctional nonreciprocal quantum device based on the integration and tunable interaction of superconducting quantum circuit (SQC) is designed. This device can switch between two‐port isolator, three‐port symmetric circulator, and antisymmetric circulator under the control of external magnetic flux. Furthermore, both isolator and circulator can achieve nearly perfect unidirectional signal transmission. It is believed that this scalable and integrable nonreciprocal device can provide new insight for the development of large‐scale quantum networks.

DOI
10.1002/qute.202500045

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Abstract Nonreciprocal devices, such as isolator or circulator, are crucial for information routing and processing in quantum networks. Traditional nonreciprocal devices, which rely on the application of bias magnetic fields to break time‐reversal symmetry and Lorentz reciprocity, tend to be bulky and require strong static magnetic fields. This makes them challenging to implement in highly integrated large‐scale quantum networks. Therefore, a multifunctional nonreciprocal quantum device based on the integration and tunable interaction of superconducting quantum circuit (SQC) is designed. This device can switch between two‐port isolator, three‐port symmetric circulator, and antisymmetric circulator under the control of external magnetic flux. Furthermore, both isolator and circulator can achieve nearly perfect unidirectional signal transmission. It is believed that this scalable and integrable nonreciprocal device can provide new insight for the development of large‐scale quantum networks.
Abstract In quantum information detection, significant interest has recently emerged in replacing conventional ferrite circulators with superconducting magnetic-free nonreciprocal devices. However, superconducting non-reciprocal devices with simpler structures and easier manufacturing processes still require further development. Inspired by conventional microwave circuits, we demonstrate a superconducting nonreciprocal circulator by parametric modulation of three identical, strongly and symmetrically coupled resonators. The circulator requires only three DC superconducting quantum interference devices, achieving an isolation of 20 dB , insertion loss of 0.47 dB , and return loss better than 25 dB over an instantaneous bandwidth of 50 MHz . The center frequency of the circulator is tunable within the range of 4– 8 GHz . Detailed design considerations for the experimental realization of a three-port superconducting circulator are presented, together with simulation results for a four-port circulator. Compared with previously reported superconducting magnetic-free nonreciprocal devices, the proposed circulator features a simpler circuit topology, demonstrating strong potential for scalable superconducting quantum information detection.
This thesis develops theory for and experimentally demonstrates a new way to break Lorentz reciprocity—the symmetry, in an electrical network, under exchange of source and detector. The approach is based on the sequential application of frequency conversion and delay; as frequency and time are Fourier duals, these operations do not generally commute. We apply this method in the construction of an on-chip superconducting microwave circulator, a critical component for the unidirectional routing of quantum information in superconducting networks. The device requires neither permanent magnets nor microwave control tones, allowing on-chip integration with other superconducting circuits without expensive control hardware. Isolation in the device exceeds 20 dB over a bandwidth of tens of MHz, and its insertion loss is small, reaching as low as 0.9 dB at select operation frequencies. Furthermore, the device is linear with respect to input power for signal powers up to many hundreds of fW (~103 circulating photons), and the direction of circulation can be dynamically reconfigured. We demonstrate its tunability with operation at a selection of frequencies between 4 and 6 GHz. Given the current status of quantum error-correction and architectures for quantum information processing with superconducting circuits, such scalable non-reciprocal devices will almost certainly be necessary for construction of a superconducting quantum computer intended to be more than a proof-of-principle.
Introducing new components and functionalities into quantum devices is critical in advancing state-of-the-art hardware. Here, we propose superconducting diodes (SDs) as a coherent nonreciprocal element in circuit quantum electrodynamics (cQED) architectures. In particular, we use an asymmetric SQUID as an SD controlled with a flux bias - nonreciprocal element with single control handle and on-chip modality. We spectroscopically characterize SD and show that flux bias acts cooperatively with the nonlinear diode response to induce direction-dependent resonance shifts in the transmission spectrum. We show that even with modest diode efficiency the isolation isolation ratio is sufficiently high, and scales with multiple SDs. We demonstrate the use of the SD as a coupler to realize coherent nonreciprocal qubit-qubit coupling. With a minimal two qubit system, we demonstrate nonreciprocal half-iSWAP, thereby showcasing the potential of intrinsic nonreciprocity as a tool to perform arbitrary two-qubit gates. Our work enables high-fidelity signal routing and entanglement generation in all-to-all connected microwave quantum networks, where nonreciprocity is embedded at the device level.
We report on the design and performance of an on-chip microwave circulator with a widely (GHz) tunable operation frequency.Nonreciprocity is created with a combination of frequency conversion and delay, and requires neither permanent magnets nor microwave bias tones, allowing on-chip integration with other superconducting circuits without the need for high-bandwidth control lines.Isolation in the device exceeds 20 dB over a bandwidth of tens of MHz, and its insertion loss is small, reaching as low as 0.9 dB at select operation frequencies.Furthermore, the device is linear with respect to input power for signal powers up to hundreds of fW (≈10 3 circulating photons), and the direction of circulation can be dynamically reconfigured.We demonstrate its operation at a selection of frequencies between 4 and 6 GHz.
Nonreciprocal photon transmissions at the single-quantum level play crucial roles in optical information processing. Here, we propose to develop a nonreciprocal photonic quantum router via synthetic magnetism, which can route photons of an input quantum state in one direction but block them in the other direction. Our model is based on a superconducting circuit of linearly coupled microwave cavities, and the Lorentz reciprocity is broken by synthesizing an effective magnetic field for photons. As a result, an input quantum signal from a given direction can be delivered on-demand to either of the two output ports, but it from the opposite direction is completely absorbed. Our scheme does not involve strong static magnetic fields and optical nonlinearity for generating the desired optical nonreciprocity. It is, therefore, expected to be a key ingredient for the construction of on-chip quantum networks.
Nonreciprocal optical devices are essential for laser protection, modern optical communication and quantum information processing by enforcing one-way light propagation. The conventional Faraday magneto-optical nonreciprocal devices rely on a strong magnetic field, which is provided by a permanent magnet. As a result, the isolation direction of such devices is fixed and severely restricts their applications in quantum networks. In this work, we experimentally demonstrate the simultaneous one-way transmission and unidirectional reflection by using a magneto-optical Fabry–Pérot cavity and a magnetic field strength of 50 mT. An optical isolator and a three-port quasi-circulator are realized based on this nonreciprocal cavity system. The isolator achieves an isolation ratio of up to 22 dB and an averaged insertion loss down to 0.97 dB. The quasi-circulator is realized with a fidelity exceeding 99% and an overall survival probability of 89.9%, corresponding to an insertion loss of ∼0.46 dB. The magnetic field is provided by an electromagnetic coil, thereby allowing for reversing the light circulating path. The reversible quasi-circulator paves the way for building reconfigurable quantum networks.