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:2602.11576 · Journal of the Physical Society of Japan

Control the qubit-qubit coupling with double superconducting resonators

Hui Wang, Rui Wang, Daichi Sugiyama, J. S. Tsai

quant-phSubmitted Feb 12, 2026• Announced Feb 13, 2026• 0 citations
v1 · Feb 12, 2026v2 · Feb 25, 2026
arXivHTMLPDF

Abstract

We experimentally studied the switching off processes in the double-resonator coupler superconducting quantum circuit.In both frequency and time-domain, we observed the variation of qubit-qubit effective coupling by tuning qubits'frequencies. According to the measurement results, by just shifting qubits' frequencies smaller than 50 MHz, the effective qubit-qubit coupling strength can be tuned from switching off point to two qubit gate point (effective coupling larger than 5 MHz) in double-resonator superconducting quantum circuit. The double-resonator coupler superconducting quantum circuit has the advantage of simple fabrications, introducing less flux noises, reducing occupancy of dilution refrigerator cables, which might supply a promising platform for future large-scale superconducting quantum processors.

Journal reference
J. Phys. Soc. Jpn. 95, 074301 (2026)
DOI
10.7566/JPSJ.95.074301
Comments
7 pages, 9 figures

Related papers

Controlling the qubit-qubit coupling in the superconducting circuit with double-resonator couplers

Hui Wang, Yan-Jun Zhao, Hui-Chen Sun +5 more

We propose a theoretical scheme of using two fixed-frequency resonator couplers to tune the interaction between two Xmon qubits. The indirect interaction between two qubits induced by two resonators can cancel each other, so direct qubit-qubit coupling is not essential for the switching off. So, we can suppress the static ZZ coupling with the weak direct qubit-qubit coupling and even eliminate the static ZZ coupling through the destructive interferences of the double-path couplers. The cross-Kerr resonance can induce additional poles for the static ZZ coupling which should be kept away during the two-qubit gates. The double-resonator couplers scheme could unfreeze some restrictions during the design of superconducting quantum chips and mitigate the static ZZ coupling, which might supply a promising platform for future superconducting quantum chips.

arXiv:2304.10047•Physical Review A•Jan 2, 2024•10 citations

A double-resonator coupler for high-fidelity two-qubit gates between superconducting qubits

Seunghyeon Jin, Seungha Woo, Shinyoung Hwang +6 more

Tunable couplers have enabled two-qubit gate fidelities in superconducting quantum processors to approach $99.9\%$, yet simultaneously suppressing residual interactions and maintaining flexible qubit-frequency allocation remain central challenges for scaling. Here, we propose a double-resonator coupler (DRC) consisting of two resonators interconnected by a single Josephson junction and a capacitor. The hybridized resonator modes provide two mediated exchange paths whose interference controls the qubit-qubit interaction. The DRC enables complete cancellation of residual $ZZ$ interaction for qubit-qubit detunings well outside the straddling regime, even in the absence of direct qubit-qubit coupling, thereby relaxing constraints on frequency allocation and qubit placement. Away from the idle point, the same circuit provides a strong $ZZ$ interaction of approximately $70\,\mathrm{MHz}$, enabling a $20\,\mathrm{ns}$ controlled-Z gate with simulated coherent infidelity below $10^{-5}$. These results establish the DRC as a flexible single-junction coupler architecture for high-fidelity superconducting quantum processors.

quant-pharXiv:2609.05222•Sep 7, 2026•0 citations

In situ Qubit Frequency Tuning Circuit for Scalable Superconducting Quantum Computing: Scheme and Experiment

Jiang, Lei, Yu Xu, Li, Shaowei +30 more

Frequency tunable qubit plays a significant role for scalable superconducting quantum processors. The state-of-the-art room-temperature electronics for tuning qubit frequency suffers from unscalable limit, such as heating problem, linear growth of control cables, etc. Here we propose a scalable scheme to tune the qubit frequency by using in situ superconducting circuit, which is based on radio frequency superconducting quantum interference device (rf-SQUID). We demonstrate both theoretically and experimentally that the qubit frequency could be modulated by inputting several single pulses into rf-SQUID. Compared with the traditional scheme, our scheme not only solves the heating problem, but also provides the potential to exponentially reduce the number of cables inside the dilute refrigerator and the room-temperature electronics resource for tuning qubit frequency, which is achieved by a time-division-multiplex (TDM) scheme combining rf-SQUID with switch arrays. With such TDM scheme, the number of cables could be reduced from the usual $\sim 3n$ to $\sim \log_2{(3n)} + 1$ for two-dimensional quantum processors comprising $n$ qubits and $\sim 2n$ couplers. Our work paves the way for large-scale control of superconducting quantum processor.

arXiv:2407.21415•Jul 31, 2024•1 citation

Tunable Coupler for Realizing a Controlled-Phase Gate with Dynamically Decoupled Regime in a Superconducting Circuit

X. Li, T. Cai, H. Yan +13 more

Controllable interaction between superconducting qubits is desirable for large-scale quantum computation and simulation. Here, based on a theoretical proposal by Yan et al. [Phys. Rev. Appl. 10, 054061 (2018)] we experimentally demonstrate a simply designed and flux-controlled tunable coupler with a continuous tunability by adjusting the coupler frequency, which can completely turn off adjacent superconducting qubit coupling. Utilizing the tunable interaction between two qubits via the coupler, we implement a different type of controlled-phase (cz) gate with ``dynamically decoupled regime,'' which allows the qubit-qubit coupling to be only ``on'' at the usual operating point while dynamically ``off'' during the tuning process of one qubit frequency into and out of the operating point. This scheme not only efficiently suppresses the leakage out of the computational subspace, but also allows for the acquired two-qubit phase being geometric at the operating point. We achieve an average cz gate fidelity of $98.3\ifmmode\pm\else\textpm\fi{}0.6\mathrm{%}$, which is dominantly limited by qubit decoherence. The demonstrated tunable coupler provides a desirable tool to suppress adjacent qubit coupling and is suitable for large-scale quantum computation and simulation.

arXiv:1912.10721•Physical Review Applied•Aug 25, 2020•117 citations

Cooper-Pair Box Coupled to Two Resonators: An Architecture for a Quantum Refrigerator

Andrew Guthrie, Christoforus Dimas Satrya, Yu-Cheng Chang +3 more

Superconducting circuits present a promising platform with which to realize a quantum refrigerator. Motivated by this, we fabricate and perform spectroscopy of a gated Cooper-pair box, capacitively coupled to two superconducting coplanar-waveguide resonators with different frequencies. We experimentally demonstrate the strong coupling of a charge qubit to two superconducting resonators, with the ability to perform voltage driving of the qubit at gigahertz frequencies. We go on to discuss how the measured device could be modified to operate as a cyclic quantum refrigerator by terminating the resonators with normal-metal resistors acting as heat baths.

arXiv:2109.03023•Physical Review Applied•Jun 10, 2022•29 citations

Coherent Tunable Coupling of Quantum Circuits

Michael S. Allman

This thesis presents a detailed investigation of coherent tunable coupling between two coupled quantum circuits. Quantum circuits have the potential to be used as the fundamental building blocks in quantum processors. Any large scale quantum processor will be composed of a large number of these coupled circuits. The efficient implementation of quantum algorithms will be difficult without a reliable mechanism for controlling the interaction strength between coupled systems, while preserving the delicate quantum information stored in the coherent superpositions of quantum states. We show that a flux-biased rf-SQUID can be used to coherently mediate the interaction between two coupled quantum circuits, a phase qubit and LC resonator. This interaction results from an effective mutual inductance between the qubit and resonator as a result of their direct coupling to the rf-SQUID. The sign and magnitude of this effective mutual inductance can be tuned with applied flux to the rf-SQUID, thus controlling the coupled interactions over a large range. We observe the modulation in coupling strength using measurements in both the frequency and time domains. The measurements are shown to agree well with theoretical predictions. This thesis discusses all aspects of the experiments from a theoretical description of each component to the design, fabrication, experimental setup and measurements.

•Jan 1, 2011•0 citations
We experimentally studied the switching off processes in the double-resonator coupler superconducting quantum circuit.In both frequency and time-domain, we observed the variation of qubit-qubit effective coupling by tuning qubits'frequencies. According to the measurement results, by just shifting qubits' frequencies smaller than 50 MHz, the effective qubit-qubit coupling strength can be tuned from switching off point to two qubit gate point (effective coupling larger than 5 MHz) in double-resonator superconducting quantum circuit. The double-resonator coupler superconducting quantum circuit has the advantage of simple fabrications, introducing less flux noises, reducing occupancy of dilution refrigerator cables, which might supply a promising platform for future large-scale superconducting quantum processors.
We propose a theoretical scheme of using two fixed-frequency resonator couplers to tune the interaction between two Xmon qubits. The indirect interaction between two qubits induced by two resonators can cancel each other, so direct qubit-qubit coupling is not essential for the switching off. So, we can suppress the static ZZ coupling with the weak direct qubit-qubit coupling and even eliminate the static ZZ coupling through the destructive interferences of the double-path couplers. The cross-Kerr resonance can induce additional poles for the static ZZ coupling which should be kept away during the two-qubit gates. The double-resonator couplers scheme could unfreeze some restrictions during the design of superconducting quantum chips and mitigate the static ZZ coupling, which might supply a promising platform for future superconducting quantum chips.
Tunable couplers have enabled two-qubit gate fidelities in superconducting quantum processors to approach 99.9%99.9\%99.9%, yet simultaneously suppressing residual interactions and maintaining flexible qubit-frequency allocation remain central challenges for scaling. Here, we propose a double-resonator coupler (DRC) consisting of two resonators interconnected by a single Josephson junction and a capacitor. The hybridized resonator modes provide two mediated exchange paths whose interference controls the qubit-qubit interaction. The DRC enables complete cancellation of residual ZZZZZZ interaction for qubit-qubit detunings well outside the straddling regime, even in the absence of direct qubit-qubit coupling, thereby relaxing constraints on frequency allocation and qubit placement. Away from the idle point, the same circuit provides a strong ZZZZZZ interaction of approximately 70 MHz70\,\mathrm{MHz}70MHz, enabling a 20 ns20\,\mathrm{ns}20ns controlled-Z gate with simulated coherent infidelity below 10−510^{-5}10−5. These results establish the DRC as a flexible single-junction coupler architecture for high-fidelity superconducting quantum processors.
Frequency tunable qubit plays a significant role for scalable superconducting quantum processors. The state-of-the-art room-temperature electronics for tuning qubit frequency suffers from unscalable limit, such as heating problem, linear growth of control cables, etc. Here we propose a scalable scheme to tune the qubit frequency by using in situ superconducting circuit, which is based on radio frequency superconducting quantum interference device (rf-SQUID). We demonstrate both theoretically and experimentally that the qubit frequency could be modulated by inputting several single pulses into rf-SQUID. Compared with the traditional scheme, our scheme not only solves the heating problem, but also provides the potential to exponentially reduce the number of cables inside the dilute refrigerator and the room-temperature electronics resource for tuning qubit frequency, which is achieved by a time-division-multiplex (TDM) scheme combining rf-SQUID with switch arrays. With such TDM scheme, the number of cables could be reduced from the usual ∼3n\sim 3n∼3n to ∼log⁡2(3n)+1\sim \log_2{(3n)} + 1∼log2​(3n)+1 for two-dimensional quantum processors comprising nnn qubits and ∼2n\sim 2n∼2n couplers. Our work paves the way for large-scale control of superconducting quantum processor.
Controllable interaction between superconducting qubits is desirable for large-scale quantum computation and simulation. Here, based on a theoretical proposal by Yan et al. [Phys. Rev. Appl. 10, 054061 (2018)] we experimentally demonstrate a simply designed and flux-controlled tunable coupler with a continuous tunability by adjusting the coupler frequency, which can completely turn off adjacent superconducting qubit coupling. Utilizing the tunable interaction between two qubits via the coupler, we implement a different type of controlled-phase (cz) gate with ``dynamically decoupled regime,'' which allows the qubit-qubit coupling to be only ``on'' at the usual operating point while dynamically ``off'' during the tuning process of one qubit frequency into and out of the operating point. This scheme not only efficiently suppresses the leakage out of the computational subspace, but also allows for the acquired two-qubit phase being geometric at the operating point. We achieve an average cz gate fidelity of $98.3\ifmmode\pm\else\textpm\fi{}0.6\mathrm{%}$, which is dominantly limited by qubit decoherence. The demonstrated tunable coupler provides a desirable tool to suppress adjacent qubit coupling and is suitable for large-scale quantum computation and simulation.
Superconducting circuits present a promising platform with which to realize a quantum refrigerator. Motivated by this, we fabricate and perform spectroscopy of a gated Cooper-pair box, capacitively coupled to two superconducting coplanar-waveguide resonators with different frequencies. We experimentally demonstrate the strong coupling of a charge qubit to two superconducting resonators, with the ability to perform voltage driving of the qubit at gigahertz frequencies. We go on to discuss how the measured device could be modified to operate as a cyclic quantum refrigerator by terminating the resonators with normal-metal resistors acting as heat baths.
This thesis presents a detailed investigation of coherent tunable coupling between two coupled quantum circuits. Quantum circuits have the potential to be used as the fundamental building blocks in quantum processors. Any large scale quantum processor will be composed of a large number of these coupled circuits. The efficient implementation of quantum algorithms will be difficult without a reliable mechanism for controlling the interaction strength between coupled systems, while preserving the delicate quantum information stored in the coherent superpositions of quantum states. We show that a flux-biased rf-SQUID can be used to coherently mediate the interaction between two coupled quantum circuits, a phase qubit and LC resonator. This interaction results from an effective mutual inductance between the qubit and resonator as a result of their direct coupling to the rf-SQUID. The sign and magnitude of this effective mutual inductance can be tuned with applied flux to the rf-SQUID, thus controlling the coupled interactions over a large range. We observe the modulation in coupling strength using measurements in both the frequency and time domains. The measurements are shown to agree well with theoretical predictions. This thesis discusses all aspects of the experiments from a theoretical description of each component to the design, fabrication, experimental setup and measurements.