Hardware-Efficient Microwave-Activated Tunable Coupling between Superconducting Qubits

Bradley K Mitchell; Ravi K Naik; Alexis Morvan; Akel Hashim; John Mark Kreikebaum; Brian Marinelli; Wim Lavrijsen; Kasra Nowrouzi; David I Santiago; Irfan Siddiqi

doi:10.1103/PhysRevLett.127.200502

Hardware-Efficient Microwave-Activated Tunable Coupling between Superconducting Qubits

Phys Rev Lett. 2021 Nov 12;127(20):200502. doi: 10.1103/PhysRevLett.127.200502.

Authors

Bradley K Mitchell^{1

2}, Ravi K Naik^{1

2}, Alexis Morvan^{1

2}, Akel Hashim^{1

2}, John Mark Kreikebaum^{1

3}, Brian Marinelli^{1

2}, Wim Lavrijsen², Kasra Nowrouzi^{1

2}, David I Santiago^{1

2}, Irfan Siddiqi^{1

2

3}

Affiliations

¹ Quantum Nanoelectronics Laboratory, University of California, Berkeley, Berkeley, California 94720, USA.
² Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
³ Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.

PMID: 34860047
DOI: 10.1103/PhysRevLett.127.200502

Abstract

Generating high-fidelity, tunable entanglement between qubits is crucial for realizing gate-based quantum computation. In superconducting circuits, tunable interactions are often implemented using flux-tunable qubits or coupling elements, adding control complexity and noise sources. Here, we realize a tunable ZZ interaction between two transmon qubits with fixed frequencies and fixed coupling, induced by driving both transmons off resonantly. We show tunable coupling over 1 order of magnitude larger than the static coupling, and change the sign of the interaction, enabling cancellation of the idle coupling. Further, this interaction is amenable to large quantum processors: the drive frequency can be flexibly chosen to avoid spurious transitions, and because both transmons are driven, it is resilient to microwave cross talk. We apply this interaction to implement a controlled phase (CZ) gate with a gate fidelity of 99.43(1)% as measured by cycle benchmarking, and we find the fidelity is limited by incoherent errors.