Unimon qubit

Abstract

Superconducting qubits are one of the most promising candidates to implement quantum computers. The superiority of superconducting quantum computers over any classical device in simulating random but well-determined quantum circuits has already been shown in two independent experiments and important steps have been taken in quantum error correction. However, the currently wide-spread qubit designs do not yet provide high enough performance to enable practical applications or efficient scaling of logical qubits owing to one or several following issues: sensitivity to charge or flux noise leading to decoherence, too weak non-linearity preventing fast operations, undesirably dense excitation spectrum, or complicated design vulnerable to parasitic capacitance. Here, we introduce and demonstrate a superconducting-qubit type, the unimon, which combines the desired properties of high non-linearity, full insensitivity to dc charge noise, insensitivity to flux noise, and a simple structure consisting only of a single Josephson junction in a resonator. We measure the qubit frequency, ${\omega }_{01}/(2\pi )$, and anharmonicity $\alpha$ over the full dc-flux range and observe, in agreement with our quantum models, that the qubit anharmonicity is greatly enhanced at the optimal operation point, yielding, for example, 99.9% and 99.8% fidelity for 13-ns single-qubit gates on two qubits with $({\omega }_{01},\alpha )=(4.49\mathrm{GHz},434\mathrm{MHz})\times 2\pi$ and $(3.55\mathrm{GHz},744\mathrm{MHz})\times 2\pi$, respectively. The energy relaxation time $T_1\lesssim 10\mu \mathrm{s}$ is stable for hours and seems to be limited by dielectric losses. Thus, future improvements of the design, materials, and gate time may promote the unimon to break the 99.99% fidelity target for efficient quantum error correction and possible quantum advantage with noisy systems.

Main text: 37 pages,10 figures, 3 tables. Supplementary: 34 pages, 8 figure, 1 table

References in corpus (12)

• Supplementary information for "Quantum supremacy using a programmable superconducting processor"
• Charge insensitive qubit design derived from the Cooper pair box
• Surface codes: Towards practical large-scale quantum computation
• Strong quantum computational advantage using a superconducting quantum processor
• Suppressing quantum errors by scaling a surface code logical qubit
• Dynamical decoupling and noise spectroscopy with a superconducting flux qubit
• Simple pulses for elimination of leakage in weakly nonlinear qubits
• Robust randomized benchmarking of quantum processes
• Microwave-induced coupling of superconducting qubits
• Josephson junction-embedded transmission-line resonators: from Kerr medium to in-line transmon
• Matching and maximum likelihood decoding of a multi-round subsystem quantum error correction experiment
• Engineering Framework for Optimizing Superconducting Qubit Designs

Cited by in corpus (15)

• Reducing leakage of single-qubit gates for superconducting quantum processors using analytical control pulse envelopes
• Measurement-Induced Transmon Ionization
• Smoking-gun signatures of non-Markovianity of a superconducting qubit
• Calibration of Drive Non-Linearity for Arbitrary-Angle Single-Qubit Gates Using Error Amplification
• Characterization of a Transmon Qubit in a 3D Cavity for Quantum Machine Learning and Photon Counting
• Enhancing qubit readout with Bayesian Learning
• Nonlinear response theory for lossy superconducting quantum circuits
• Input-Output Hierarchical Equations Of Motion
• The quartic Blochnium: an anharmonic quasicharge superconducting qubit
• Quantum Feasibility Labeling for NP-complete Vertex Coloring Problem
• Parameter optimization for the unimon qubit
• Bayesian mitigation of measurement errors in multiqubit experiments
• Enhancing Quantum Algorithms for Quadratic Unconstrained Binary Optimization via Integer Programming
• Tunable Hybrid-Mode Coupler Enabling Strong Interactions between Transmons at Centimeter-Scale Distance
• Robust multi-mode superconducting circuit optimized for quantum information processing