Experimental realization of nonadiabatic geometric gates with a superconducting Xmon qubit

TL;DR

This paper demonstrates high-fidelity nonadiabatic geometric quantum gates on a superconducting Xmon qubit, utilizing only the two lowest energy levels to improve gate fidelity and noise resilience.

Contribution

The work experimentally realizes Abelian-geometric-phase-based nonadiabatic gates on an Xmon qubit using only the lowest two levels, avoiding issues from short coherence of higher levels.

Findings

Average gate fidelity up to 99.6% (quantum process tomography)

Average fidelity up to 99.7% (randomized benchmarking)

Successful implementation of nonadiabatic geometric gates with improved robustness

Abstract

Geometric phases are only dependent on evolution paths but independent of evolution details so that they own some intrinsic noise-resilience features. Based on different geometric phases, various quantum gates have been proposed, such as nonadiabatic geometric gates based on nonadiabatic Abelian geometric phases and nonadiabatic holonomic gates based on nonadiabatic non-Abelian geometric phases. Up to now, nonadiabatic holonomic one-qubit gates have been experimentally demonstrated with the supercondunting transmon, where three lowest levels with cascaded configuration are all applied in the operation. However, the second excited states of transmons have relatively short coherence time, which results in a lessened fidelity of quantum gates. Here, we experimentally realize Abelian-geometric-phase-based nonadiabatic geometric one-qubit gates with a superconducting Xmon qubit. The realization is performed on two lowest levels of an Xmon qubit and thus avoids the influence from the short coherence time of the second excited state. The experimental result indicates that the average fidelities of single-qubit gates can be up to 99.6% and 99.7% characterized by quantum process tomography and randomized benchmarking, respectively.