A challenge for constructing large circuits of superconducting qubits is to balance addressability, coherence and coupling strength. High coherence can be attained by building circuits from fixed-frequency qubits, however, leading techniques cannot couple qubits that are far detuned. Here we introduce a method based on a tunable bus which allows for the coupling of two fixed-frequency qubits even at large detunings. By parametrically oscillating the bus at the qubit-qubit detuning we enable a resonant exchange (XX+YY) interaction. We use this interaction to implement a 183ns two-qubit iSWAP gate between qubits separated in frequency by 854MHz with a measured average fidelity of 0.9823(4) from interleaved randomized benchmarking. This gate may be an enabling technology for surface code circuits and for analog quantum simulation.
@article{arxiv.1604.03076,
title = {A universal gate for fixed-frequency qubits via a tunable bus},
author = {David C. McKay and Stefan Filipp and Antonio Mezzacapo and Easwar Magesan and Jerry M. Chow and Jay M. Gambetta},
journal= {arXiv preprint arXiv:1604.03076},
year = {2016}
}
Comments
Fixed minor errors, added references and improved figure readability. 10 pages, 6 figures