We report on the design and performance of an on-chip microwave circulator with a widely (GHz) tunable operation frequency. Non-reciprocity is created with a combination of frequency conversion and delay, and requires neither permanent magnets nor microwave bias tones, allowing on-chip integration with other superconducting circuits without the need for high-bandwidth control lines. Isolation in the device exceeds 20 dB over a bandwidth of tens of MHz, and its insertion loss is small, reaching as low as 0.9 dB at select operation frequencies. Furthermore, the device is linear with respect to input power for signal powers up to hundreds of fW (≈103 circulating photons), and the direction of circulation can be dynamically reconfigured. We demonstrate its operation at a selection of frequencies between 4 and 6 GHz.
@article{arxiv.1707.04565,
title = {Widely tunable on-chip microwave circulator for superconducting quantum circuits},
author = {Benjamin J. Chapman and Eric I. Rosenthal and Joseph Kerckhoff and Bradley A. Moores and Leila R. Vale and Gene C. Hilton and Kevin Lalumière and Alexandre Blais and K. W. Lehnert},
journal= {arXiv preprint arXiv:1707.04565},
year = {2017}
}