A persistent-current-biased and current-actuated switch for superconducting circuits

TL;DR

This paper introduces a superconducting microwave switch that uses persistent current bias and direct current actuation, reducing power consumption and crosstalk, with high isolation, power handling, and broad bandwidth suitable for quantum circuits.

Contribution

The authors design and demonstrate a superconducting switch employing persistent current bias and direct current actuation, improving power efficiency and integration for quantum information processing.

Findings

Achieves over 20 dB isolation in off mode

Handles power greater than 100 pW for resonator readout

Offers modulation bandwidth broader than 600 MHz

Abstract

Broadband and low-loss superconducting switches can facilitate large-scale quantum information processors and cryogenic detectors by dynamically reconfiguring the connectivity of their circuits. The time dependent connectivity is enabled by the nonlinearity of lossless Josephson junctions, which are often wired into superconducting loops to be controlled by magnetic flux. However, this approach needs a power-consuming constant flux bias and dynamic flux actuation, both of which are hard to isolate from other switches or flux sensitive elements, limiting their integration density. Here, we design and characterize a microwave switch that implements a persistent current bias and direct current actuation to reduce static power consumption, actuation energy and potential crosstalk to other devices. We show that persistent current associated with tens of flux quanta is stable and long-lived, reducing the need for on-the-fly tuning. We further demonstrate that our switch has desirable performance for superconducting-circuit-based quantum information processing, including an off mode with more than 20 dB isolation comparable to commercial ferrite isolators, power handling larger than 100 pW sufficient for resonator readout tones and amplifier pumps, and modulation bandwidth broader than 600 MHz useful for multiplexing schemes.