Unimon qubit

• URL: http://arxiv.org/abs/2203.05896v2
• Date: Tue, 5 Apr 2022 14:16:21 GMT
• Title: Unimon qubit
• Authors: Eric Hyypp\"a, Suman Kundu, Chun Fai Chan, Andr\'as Gunyh\'o, Juho Hotari, David Janzso, Kristinn Juliusson, Olavi Kiuru, Janne Kotilahti, Alessandro Landra, Wei Liu, Fabian Marxer, Akseli M\"akinen, Jean-Luc Orgiazzi, Mario Palma, Mykhailo Savytskyi, Francesca Tosto, Jani Tuorila, Vasilii Vadimov, Tianyi Li, Caspar Ockeloen-Korppi, Johannes Heinsoo, Kuan Yen Tan, Juha Hassel and Mikko M\"ott\"onen
• Abstract summary: Superconducting qubits are one of the most promising candidates to implement quantum computers. 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.
• Score: 42.83899285555746
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• 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.

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