Coherent interaction-free detection of microwave pulses with a superconducting circuit

TL;DR

This paper introduces and experimentally demonstrates a novel coherent interaction-free detection method using a superconducting transmon circuit, enabling detection of microwave pulses without exciting the device.

Contribution

It presents the first implementation of coherent interaction-free detection with superconducting circuits, achieving higher success probability than traditional projection-based methods.

Findings

Successfully detected microwave pulses without exciting the transmon's third level

Achieved higher success probability compared to standard interaction-free measurements

Demonstrated the protocol using Ramsey microwave pulses and ground-state monitoring

Abstract

The interaction-free measurement is a fundamental quantum effect whereby the presence of a photosensitive object is determined without irreversible photon absorption. Here we propose the concept of coherent interaction-free detection and demonstrate it experimentally using a three-level superconducting transmon circuit. In contrast to standard interaction-free measurement setups, where the dynamics involves a series of projection operations, our protocol employs a fully coherent evolution that results, surprisingly, in a higher probability of success. We show that it is possible to ascertain the presence of a microwave pulse resonant with the second transition of the transmon, while at the same time avoid exciting the device onto the third level. Experimentally, this is done by using a series of Ramsey microwave pulses coupled into the first transition and monitoring the ground-state population.