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:2303.03507

Dynamically Reconfigurable Photon Exchange in a Superconducting Quantum Processor

Brian Marinelli, Luo, Jie, Hengjiang Ren, Bethany M. Niedzielski, David K. Kim, Rabindra Nath Das, Mollie E. Schwartz, David Santiago, Irfan A. Siddiqi

Published Mar 6, 2023• 7 citations
arXivHTMLPDF

Abstract

Realizing the advantages of quantum computation requires access to the full Hilbert space of states of many quantum bits (qubits). Thus, large-scale quantum computation faces the challenge of efficiently generating entanglement between many qubits. In systems with a limited number of direct connections between qubits, entanglement between non-nearest neighbor qubits is generated by a series of nearest neighbor gates, which exponentially suppresses the resulting fidelity. Here we propose and demonstrate a novel, on-chip photon exchange network. This photonic network is embedded in a superconducting quantum processor (QPU) to implement an arbitrarily reconfigurable qubit connectivity graph. We show long-range qubit-qubit interactions between qubits with a maximum spatial separation of $9.2~\text{cm}$ along a meandered bus resonator and achieve photon exchange rates up to $g_{\text{qq}} = 2π\times 0.9~\text{MHz}$. These experimental demonstrations provide a foundation to realize highly connected, reconfigurable quantum photonic networks and opens a new path towards modular quantum computing.

DOI
10.48550/arxiv.2303.03507

Related papers

Modular Quantum Processor with an All-to-All Reconfigurable Router

Xuntao Wu, Haoxiong Yan, Gustav Andersson +10 more

Superconducting qubits provide a promising approach to large-scale fault-tolerant quantum computing. However, qubit connectivity on a planar surface is typically restricted to only a few neighboring qubits. Achieving longer-range and more flexible connectivity, which is particularly appealing in light of recent developments in error-correcting codes, however, usually involves complex multilayer packaging and external cabling, which is resource intensive and can impose fidelity limitations. Here, we propose and realize a high-speed on-chip quantum processor that supports reconfigurable all-to-all coupling with a large on-off ratio. We implement the design in a four-node quantum processor, built with a modular design comprising a wiring substrate coupled to two separate qubit-bearing substrates, each including two single-qubit nodes. We use this device to demonstrate reconfigurable controlled- Z gates across all qubit pairs, with a benchmarked average fidelity of 96.00 % ± 0.08 % and best fidelity of 97.14 % ± 0.07 % , limited mainly by dephasing in the qubits. We also generate multiqubit entanglement, distributed across the separate modules, demonstrating GHZ-3 and GHZ-4 states with fidelities of 88.15 % ± 0.24 % and 75.18 % ± 0.11 % , respectively. This approach promises efficient scaling to larger-scale quantum circuits and offers a pathway for implementing quantum algorithms and error-correction schemes that benefit from enhanced qubit connectivity. Published by the American Physical Society 2024

arXiv:2407.20134•Physical Review X•Nov 4, 2024•34 citations

Reconfigurable Bus-based Quantum Router for Modular Superconducting Processors

Benzheng Yuan, chaojie Zhang, Yangyang Fei +7 more

Scaling superconducting quantum processors requires interconnects that provide both non-local connectivity and parallel entangling operations. While current quantum routers offer greater connectivity than nearest-neighbour topologies, their support for parallel, independently addressable two-qubit gates remains fundamentally limited, imposing severe compilation overheads that constitute a critical bottleneck. Here we introduce a bus-based reconfigurable quantum router that enables parallel controlled-$Z$ (CZ) gates for modular superconducting processors. Constructed from a flux-tunable SQUID network, the router selectively connects interface qubits to two shared buses, allowing destructive interference to suppress idle interactions while supporting two disjoint CZ gates in parallel. Full-system Hamiltonian simulations yield parallel-gate infidelities ranging from $7.9\times10^{-4}$ to $1.8\times10^{-3}$ under the operating conditions considered, and an open-system analysis identifies the coherence requirements for high-fidelity operation. We further assess the circuit-level consequences using hardware-aware compilation and resource-constrained scheduling. For the 36-qubit quantum Fourier transform (QFT), QAOA-MaxCut, and random-pairing circuits, the router reduces the median SWAP count by up to $34\%$ and the native CZ count by up to $20\%$ relative to a matched two-dimensional grid. Circuit-depth reductions are workload-dependent, reaching $20\%$ for QAOA-MaxCut but remaining negligible for the QFT despite its lower gate count. These results show that enhanced connectivity and schedulable parallelism provide complementary benefits for connectivity-intensive algorithms, establishing the router as a compiler-visible hardware resource and providing a scalable architectural pathway toward constructing highly connected modular superconducting quantum processors.

quant-pharXiv:2609.28881•Sep 25, 2026•0 citations

A modular quantum computer based on a quantum state router.

Chao Zhou, Pinlei Lu, Matthieu Praquin +8 more

Abstract A central challenge for realizing large-scale quantum processors is the design and realization of qubit-qubit connections: we must be able to perform efficient gates between qubits, yet prevent connections from spoiling qubit quality or prohibiting "debugging" the system. In this work, we present a microwave quantum state router that realizes all-to-all couplings among four independent and detachable quantum modules of superconducting qubits. Each module consists of a single transmon, readout mode, and communication mode coupled to the router. The router design centers on a parametrically driven, Josephson-junction based three-wave mixing element which generates photon exchange among the modules' communication modes. We first demonstrate coherent photon exchange among four communication modes, with an average full-iSWAP time of 760 ns and average inter-module gate fidelity of 0.97, limited by our modes' coherence times. We also demonstrate photon transfer and pairwise entanglement between the modules' qubits, and parallel operation of simultaneous iSWAP across the router. The gates demonstrated here can readily be extended to faster and higher-fidelity router operations, as well as scaled to support larger networks of quantum modules.

arXiv:2109.06848•May 6, 2022•8 citations

A cavity-mediated reconfigurable coupling scheme for superconducting qubits

Shinyoung Hwang, Sangyeon Lee, Eunjong Kim

Superconducting qubits have achieved remarkable progress in gate fidelity and coherence, yet their typical nearest-neighbor connectivity presents constraints for implementing complex quantum circuits. Here, we introduce a cavity-mediated coupling architecture in which a shared cavity mode, accessed through tunable qubit-cavity couplers, enables dynamically reconfigurable interactions between non-adjacent qubits. By selectively activating the couplers, we demonstrate that high-fidelity iSWAP and CZ gates can be performed within 50 ns with simulated coherent error below $10^{-4}$, while residual $ZZ$ interaction during idling remains below a few kilohertz. Extending to a four-qubit system, we also simulate gates between every qubit pair by selectively enabling the couplers with low qubit crosstalk. This approach provides a practical route toward enhanced interaction flexibility in superconducting quantum processors and may serve as a useful building block for devices that benefit from selective non-local coupling.

quant-pharXiv:2602.08869•Feb 10, 2026•0 citations

Implementation of high-fidelity two-qubit gates across separate superconducting quantum chips via a bus resonator

Shu-Ya Wang, Dong-Sheng Wang, Xiao-Han Yu +7 more

High-fidelity quantum interconnection remains a critical challenge for scaling up superconducting quantum chips. Here, we realize a simple fixed coupling scheme to achieve high-fidelity two-qubit gate operation across separate superconducting quantum chips. In this scheme, qubit-qubit coupling between separate chips can be realized via exchange interaction mediated by a bus resonator. By merely tuning the frequency of a single qubit, the resonant mode of the bus resonator can be modulated, enabling high-quality and stable quantum interconnection across different chips. Consequently, the experimentally implemented two-qubit gate operations between separate chips exhibit excellent performance, with a maximum two-qubit CZ gate fidelity reaching 99.57%. This work lays a technical foundation for the realization of high-fidelity chip-to-chip quantum interconnection, which facilitates the development of large-scale superconducting quantum chips with high fidelity.

EPJ Quantum Technology•Jul 9, 2026•0 citations

Programmable photonic integrated meshes for modular generation of optical entanglement links

Mark Dong, Matthew Zimmermann, David Heim +9 more

Abstract Large-scale generation of quantum entanglement between individually controllable qubits is at the core of quantum computing, communications, and sensing. Modular architectures of remotely-connected quantum technologies have been proposed for a variety of physical qubits, with demonstrations reported in atomic and all-photonic systems. However, an open challenge in these architectures lies in constructing high-speed and high-fidelity reconfigurable photonic networks for optically-heralded entanglement among target qubits. Here we introduce a programmable photonic integrated circuit (PIC), realized in a piezo-actuated silicon nitride (SiN)-in-oxide CMOS-compatible process, that implements an N × N Mach–Zehnder mesh (MZM) capable of high-speed execution of linear optical transformations. The visible-spectrum photonic integrated mesh is programmed to generate optical connectivity on up to N = 8 inputs for a range of optically-heralded entanglement protocols. In particular, we experimentally demonstrated optical connections between 16 independent pairwise mode couplings through the MZM, with optical transformation fidelities averaging 0.991 ± 0.0063. The PIC’s reconfigurable optical connectivity suffices for the production of 8-qubit resource states as building blocks of larger topological cluster states for quantum computing. Our programmable PIC platform enables the fast and scalable optical switching technology necessary for network-based quantum information processors.

arXiv:2208.13911•npj Quantum Information•Apr 27, 2023•30 citations
Realizing the advantages of quantum computation requires access to the full Hilbert space of states of many quantum bits (qubits). Thus, large-scale quantum computation faces the challenge of efficiently generating entanglement between many qubits. In systems with a limited number of direct connections between qubits, entanglement between non-nearest neighbor qubits is generated by a series of nearest neighbor gates, which exponentially suppresses the resulting fidelity. Here we propose and demonstrate a novel, on-chip photon exchange network. This photonic network is embedded in a superconducting quantum processor (QPU) to implement an arbitrarily reconfigurable qubit connectivity graph. We show long-range qubit-qubit interactions between qubits with a maximum spatial separation of 9.2 cm9.2~\text{cm}9.2 cm along a meandered bus resonator and achieve photon exchange rates up to gqq=2π×0.9 MHzg_{\text{qq}} = 2π\times 0.9~\text{MHz}gqq​=2π×0.9 MHz. These experimental demonstrations provide a foundation to realize highly connected, reconfigurable quantum photonic networks and opens a new path towards modular quantum computing.
Superconducting qubits provide a promising approach to large-scale fault-tolerant quantum computing. However, qubit connectivity on a planar surface is typically restricted to only a few neighboring qubits. Achieving longer-range and more flexible connectivity, which is particularly appealing in light of recent developments in error-correcting codes, however, usually involves complex multilayer packaging and external cabling, which is resource intensive and can impose fidelity limitations. Here, we propose and realize a high-speed on-chip quantum processor that supports reconfigurable all-to-all coupling with a large on-off ratio. We implement the design in a four-node quantum processor, built with a modular design comprising a wiring substrate coupled to two separate qubit-bearing substrates, each including two single-qubit nodes. We use this device to demonstrate reconfigurable controlled- Z gates across all qubit pairs, with a benchmarked average fidelity of 96.00 % ± 0.08 % and best fidelity of 97.14 % ± 0.07 % , limited mainly by dephasing in the qubits. We also generate multiqubit entanglement, distributed across the separate modules, demonstrating GHZ-3 and GHZ-4 states with fidelities of 88.15 % ± 0.24 % and 75.18 % ± 0.11 % , respectively. This approach promises efficient scaling to larger-scale quantum circuits and offers a pathway for implementing quantum algorithms and error-correction schemes that benefit from enhanced qubit connectivity. Published by the American Physical Society 2024
Scaling superconducting quantum processors requires interconnects that provide both non-local connectivity and parallel entangling operations. While current quantum routers offer greater connectivity than nearest-neighbour topologies, their support for parallel, independently addressable two-qubit gates remains fundamentally limited, imposing severe compilation overheads that constitute a critical bottleneck. Here we introduce a bus-based reconfigurable quantum router that enables parallel controlled-ZZZ (CZ) gates for modular superconducting processors. Constructed from a flux-tunable SQUID network, the router selectively connects interface qubits to two shared buses, allowing destructive interference to suppress idle interactions while supporting two disjoint CZ gates in parallel. Full-system Hamiltonian simulations yield parallel-gate infidelities ranging from 7.9×10−47.9\times10^{-4}7.9×10−4 to 1.8×10−31.8\times10^{-3}1.8×10−3 under the operating conditions considered, and an open-system analysis identifies the coherence requirements for high-fidelity operation. We further assess the circuit-level consequences using hardware-aware compilation and resource-constrained scheduling. For the 36-qubit quantum Fourier transform (QFT), QAOA-MaxCut, and random-pairing circuits, the router reduces the median SWAP count by up to 34%34\%34% and the native CZ count by up to 20%20\%20% relative to a matched two-dimensional grid. Circuit-depth reductions are workload-dependent, reaching 20%20\%20% for QAOA-MaxCut but remaining negligible for the QFT despite its lower gate count. These results show that enhanced connectivity and schedulable parallelism provide complementary benefits for connectivity-intensive algorithms, establishing the router as a compiler-visible hardware resource and providing a scalable architectural pathway toward constructing highly connected modular superconducting quantum processors.
Abstract A central challenge for realizing large-scale quantum processors is the design and realization of qubit-qubit connections: we must be able to perform efficient gates between qubits, yet prevent connections from spoiling qubit quality or prohibiting "debugging" the system. In this work, we present a microwave quantum state router that realizes all-to-all couplings among four independent and detachable quantum modules of superconducting qubits. Each module consists of a single transmon, readout mode, and communication mode coupled to the router. The router design centers on a parametrically driven, Josephson-junction based three-wave mixing element which generates photon exchange among the modules' communication modes. We first demonstrate coherent photon exchange among four communication modes, with an average full-iSWAP time of 760 ns and average inter-module gate fidelity of 0.97, limited by our modes' coherence times. We also demonstrate photon transfer and pairwise entanglement between the modules' qubits, and parallel operation of simultaneous iSWAP across the router. The gates demonstrated here can readily be extended to faster and higher-fidelity router operations, as well as scaled to support larger networks of quantum modules.
Superconducting qubits have achieved remarkable progress in gate fidelity and coherence, yet their typical nearest-neighbor connectivity presents constraints for implementing complex quantum circuits. Here, we introduce a cavity-mediated coupling architecture in which a shared cavity mode, accessed through tunable qubit-cavity couplers, enables dynamically reconfigurable interactions between non-adjacent qubits. By selectively activating the couplers, we demonstrate that high-fidelity iSWAP and CZ gates can be performed within 50 ns with simulated coherent error below 10−410^{-4}10−4, while residual ZZZZZZ interaction during idling remains below a few kilohertz. Extending to a four-qubit system, we also simulate gates between every qubit pair by selectively enabling the couplers with low qubit crosstalk. This approach provides a practical route toward enhanced interaction flexibility in superconducting quantum processors and may serve as a useful building block for devices that benefit from selective non-local coupling.
High-fidelity quantum interconnection remains a critical challenge for scaling up superconducting quantum chips. Here, we realize a simple fixed coupling scheme to achieve high-fidelity two-qubit gate operation across separate superconducting quantum chips. In this scheme, qubit-qubit coupling between separate chips can be realized via exchange interaction mediated by a bus resonator. By merely tuning the frequency of a single qubit, the resonant mode of the bus resonator can be modulated, enabling high-quality and stable quantum interconnection across different chips. Consequently, the experimentally implemented two-qubit gate operations between separate chips exhibit excellent performance, with a maximum two-qubit CZ gate fidelity reaching 99.57%. This work lays a technical foundation for the realization of high-fidelity chip-to-chip quantum interconnection, which facilitates the development of large-scale superconducting quantum chips with high fidelity.
Abstract Large-scale generation of quantum entanglement between individually controllable qubits is at the core of quantum computing, communications, and sensing. Modular architectures of remotely-connected quantum technologies have been proposed for a variety of physical qubits, with demonstrations reported in atomic and all-photonic systems. However, an open challenge in these architectures lies in constructing high-speed and high-fidelity reconfigurable photonic networks for optically-heralded entanglement among target qubits. Here we introduce a programmable photonic integrated circuit (PIC), realized in a piezo-actuated silicon nitride (SiN)-in-oxide CMOS-compatible process, that implements an N × N Mach–Zehnder mesh (MZM) capable of high-speed execution of linear optical transformations. The visible-spectrum photonic integrated mesh is programmed to generate optical connectivity on up to N = 8 inputs for a range of optically-heralded entanglement protocols. In particular, we experimentally demonstrated optical connections between 16 independent pairwise mode couplings through the MZM, with optical transformation fidelities averaging 0.991 ± 0.0063. The PIC’s reconfigurable optical connectivity suffices for the production of 8-qubit resource states as building blocks of larger topological cluster states for quantum computing. Our programmable PIC platform enables the fast and scalable optical switching technology necessary for network-based quantum information processors.