General purpose multiplexing device for cryogenic microwave systems

TL;DR

This paper presents a versatile, broadband microwave device operable at cryogenic temperatures that enables rapid mode switching for efficient multiplexed readout in quantum systems.

Contribution

It introduces a novel three-mode microwave device capable of lossless signal processing and rapid switching, enhancing multiplexed readout protocols in circuit QED.

Findings

Achieves switching times of ≤15 ns between modes.

Demonstrates two-channel multiplexing with <1% infidelity.

Supports fast readout with up to 400 ns duration.

Abstract

We introduce and experimentally characterize a general purpose device for signal processing in circuit quantum electrodynamics systems. The device is a broadband two-port microwave circuit element with three modes of operation: it can transmit, reflect, or invert incident signals between 4 and 8 GHz. This property makes it a versatile tool for lossless signal processing at cryogenic temperatures. In particular, rapid switching (less than or equal to 15 ns) between these operation modes enables several multiplexing readout protocols for superconducting qubits. We report the device's performance in a two-channel code domain multiplexing demonstration. The multiplexed data are recovered with fast readout times (up to 400 ns) and infidelities less than 0.01 for probe powers greater than 7 fW, in agreement with the expectation for binary signaling with Gaussian noise.