Implementation of a Toffoli Gate with Superconducting Circuits

TL;DR

This paper demonstrates a superconducting circuit implementation of a Toffoli gate using transmon qubits, achieving a fidelity of approximately 68.5%, and highlights the advantages of utilizing the third energy level for more efficient gate construction.

Contribution

The work introduces a novel implementation of the Toffoli gate with superconducting transmon qubits that reduces gate complexity by exploiting higher energy levels.

Findings

Achieved a Toffoli gate fidelity of 68.5%.

Reduced gate time and complexity compared to two-level system methods.

Validated the gate performance with full process tomography.

Abstract

The quantum Toffoli gate allows universal reversible classical computation. It is also an important primitive in many quantum circuits and quantum error correction schemes. Here we demonstrate the realization of a Toffoli gate with three superconducting transmon qubits coupled to a microwave resonator. By exploiting the third energy level of the transmon qubit, the number of elementary gates needed for the implementation of the Toffoli gate, as well as the total gate time can be reduced significantly in comparison to theoretical proposals using two-level systems only. We characterize the performance of the gate by full process tomography and Monte Carlo process certification. The gate fidelity is found to be $68.5\pm0.5$%.