Implementation of a Walsh-Hadamard Gate in a Superconducting Qutrit

作者：Muhammet Ali Yurtalan, Jiahao Shi, M. Kononenko, A. Lupascu, S. Ashhab · 发表于：Physical Review Letters · 年份：2020 · DOI：10.1103/physrevlett.125.180504 · 被引用次数：75 · 研究领域：Quantum and electron transport phenomena、Quantum Information and Cryptography、Quantum Computing Algorithms and Architecture

We have implemented a Walsh-Hadamard gate, which performs a quantum Fourier transform, in a superconducting qutrit. The qutrit is encoded in the lowest three energy levels of a capacitively shunted flux device, operated at the optimal flux-symmetry point. We use an efficient decomposition of the Walsh-Hadamard gate into two unitaries, generated by off-diagonal and diagonal Hamiltonians, respectively. The gate implementation utilizes simultaneous driving of all three transitions between the three pairs of energy levels of the qutrit, one of which is implemented with a two-photon process. The gate has a duration of 35 ns and an average fidelity over a representative set of states, including preparation and tomography errors, of 99.2%, characterized with quantum-state tomography. Compensation of ac-Stark and Bloch-Siegert shifts is essential for reaching high gate fidelities.