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Tunable couplers are a key building block of superconducting quantum processors, enabling high on-off ratios for two-qubit entangling interactions. While qubit-qubit interaction can be turned off, residual wavefunctions delocalize…

Quantum Physics · Physics 2026-02-23 Zhongyi Jiang , Simon Geisert , Sören Ihssen , Ioan M. Pop , Mohammad H. Ansari

We analyze a high-fidelity two-qubit gate using fast flux pulses on superconducting fluxonium qubits. The gate is realized by temporarily detuning magnetic flux through fluxonium loop away from the half flux quantum sweet spot. We simulate…

Quantum Physics · Physics 2022-09-28 Yinqi Chen , Konstantin N. Nesterov , Vladimir E. Manucharyan , Maxim G. Vavilov

The spin states of single electrons in gate-defined quantum dots satisfy crucial requirements for a practical quantum computer. These include extremely long coherence times, high-fidelity quantum operation, and the ability to shuttle…

Building a quantum computer is a daunting challenge since it requires good control but also good isolation from the environment to minimize decoherence. It is therefore important to realize quantum gates efficiently, using as few operations…

Quantum Physics · Physics 2019-10-28 T. Bækkegaard , L. B. Kristensen , N. J. S. Loft , C. K. Andersen , D. Petrosyan , N. T. Zinner

We present a way to realize a 3-qubit quantum controlled-phase gate with superconducting qubit systems coupled to a cavity. This proposal does not require adjustment of the qubit level spacings or identical qubit-cavity coupling constants.…

Quantum Physics · Physics 2017-02-01 Chui-Ping Yang

Semiconductor spin qubits have emerged as a promising platform for quantum computing, following a significant improvement in their control fidelities over recent years. Increasing the qubit count remains challenging, beginning with the…

A double-transmon coupler (DTC) enables a fast, high-fidelity CZ gate between two highly detuned, fixed-frequency transmon qubits. Moreover, a recently proposed capacitively shunted DTC (CSDTC) realizes a small residual ZZ interaction over…

Quantum Physics · Physics 2026-05-01 Shinichi Inoue , Rui Li , Kentaro Kubo , Yinghao Ho , Yasunobu Nakamura , Hayato Goto

Exchange-coupled singlet-triplet spin qubits in two gate-defined double quantum dots are considered theoretically. Using charge density operators to describe the double-dot orbital states, we calculate the Coulomb couplings between the…

Mesoscale and Nanoscale Physics · Physics 2015-05-28 Guy Ramon

For building a scalable quantum processor with superconducting qubits, ZZ interaction is of great concern because its residual has a crucial impact to two-qubit gate fidelity. Two-qubit gates with fidelity meeting the criterion of…

Quantum Physics · Physics 2024-09-12 Peng Zhao , Peng Xu , Dong Lan , Ji Chu , Xinsheng Tan , Haifeng Yu , Yang Yu

We demonstrate an all-microwave two-qubit gate on superconducting qubits which are fixed in frequency at optimal bias points. The gate requires no additional subcircuitry and is tunable via the amplitude of microwave irradiation on one…

So far, superconducting quantum computers have certain constraints on qubit connectivity, such as nearest-neighbor couplings. To overcome this limitation, we propose a scalable architecture to simultaneously connect several pairs of distant…

Quantum Physics · Physics 2020-09-02 Roberto Stassi , Mauro Cirio , Franco Nori

Superconducting qubits have achieved exceptional gate fidelities, exceeding the error-correction threshold in recent years. One key ingredient of such improvement is the introduction of tunable couplers to control the qubit-to-qubit…

In recent years, the tunable coupling scheme has become the mainstream scheme for designing superconducting quan tum circuits. By working in the dispersive regime, the ZZ coupling and high-energy level leakage can be effectively suppressed…

Quantum Physics · Physics 2024-04-15 Tao Zhang , Chaoying Zhao

Tunable couplers enable high-fidelity two-qubit gates leveraging high on/off coupling ratios and reduced crosstalk within a single design. We investigate a galvanically connected direct-current superconducting quantum interference device…

Entanglement between atoms and microwave photons in a superconducting coplanar waveguide~(SCW) can enable hybrid quantum devices and interface static and flying qubits. We study a one-step controlled-Z~(C$_{\text{Z}}$) gate between a…

Quantum Physics · Physics 2022-12-14 Xiao-Feng Shi

A major challenge for scaling up superconducting quantum computers is unwanted couplings between qubits, which lead to always-on ZZ couplings that impact gate fidelities by shifting energy levels conditional on qubit states. To tackle this…

Quantum Physics · Physics 2024-12-30 Simon Pettersson Fors , Jorge Fernández-Pendás , Anton Frisk Kockum

Electron spin qubits in silicon are a promising platform for fault-tolerant quantum computing. Low-frequency noise, including nuclear spin fluctuations and charge noise, is a primary factor limiting gate fidelities. Suppressing this noise…

Mesoscale and Nanoscale Physics · Physics 2024-11-13 Ning Wang , Shao-Min Wang , Run-Ze Zhang , Jia-Min Kang , Wen-Long Lu , Hai-Ou Li , Gang Cao , Bao-Chuan Wang , Guo-Ping Guo

We experimentally demonstrate a parametric iSWAP gate in a superconducting circuit based on a tunable coupler for achieving a continuous tunability to eliminate unwanted qubit interactions. We implement the twoqubit iSWAP gate by applying a…

Quantum Physics · Physics 2020-09-02 X. Y. Han , T. Q. Cai , X. G. Li , Y. K. Wu , Y. W. Ma , Y. L. Ma , J. H. Wang , H. Y. Zhang , Y. P. Song , L. M. Duan

In superconducting quantum processors, exploring diverse control methods could offer essential versatility and redundancy to mitigate challenges such as frequency crowding, spurious couplings, control crosstalk, and fabrication variability,…

Quantum Physics · Physics 2026-02-13 Peng Zhao , Peng Xu , Zheng-Yuan Xue

The power of a quantum circuit is determined through the number of two-qubit entangling gates that can be performed within the coherence time of the system. In the absence of parallel quantum gate operations, this would make the quantum…

Quantum Physics · Physics 2021-05-26 Rozhin Yousefjani , Abolfazl Bayat