Demonstration of High-Fidelity Gates in a Strongly Anharmonic with Long-Coherence C-Shunt Flux Qubit

TL;DR

This paper demonstrates high-fidelity single-qubit gates on a C-shunt flux qubit with large anharmonicity and long coherence times, achieving over 99.9% fidelity, suitable for scalable quantum computing.

Contribution

It introduces a C-shunt flux qubit with combined large anharmonicity and long coherence, enabling fast, precise, and high-fidelity quantum gates.

Findings

Gate fidelity exceeds 99.9% using DRAG pulses.

Large anharmonicity suppresses leakage to higher energy levels.

Long relaxation time of 23 microseconds enhances qubit performance.

Abstract

We demonstrate high-fidelity single-qubit gates on a C-shunt flux qubit that simultaneously combines a large anharmonicity ($\mathcal{A}/2\pi=848~\mathrm{MHz}$) with long relaxation time ($T_1 = 23~\mu\text{s}$). The large anharmonicity significantly suppresses leakage to higher energy levels, enabling fast and precise microwave control. Using DRAG pulses and randomized benchmarking, the qubit achieves gate fidelities exceeding 99.9\%, highlighting the capability of C-shunt flux qubits for robust and high-performance quantum operations. These results establish them as a promising platform for scalable quantum information processing.