Parity Detection of Propagating Microwave Fields

TL;DR

This paper introduces a versatile, non-invasive parity detector for propagating microwave fields, enabling single-shot measurements and applications like Wigner tomography and Schrödinger cat state generation, advancing quantum communication and error correction.

Contribution

The paper presents a new parity detection scheme for microwaves that works in a broad frequency range and does not disturb the field's parity, useful for quantum information processing.

Findings

Successful single-shot parity detection of microwave photons.

Application to Wigner tomography of propagating microwaves.

Generation of Schrödinger cat states using the detector.

Abstract

The parity of the number of elementary excitations present in a quantum system provides important insights into its physical properties. Parity measurements are used, for example, to tomographically reconstruct quantum states or to determine if a decay of an excitation has occurred, information which can be used for quantum error correction in computation or communication protocols. Here we demonstrate a versatile parity detector for propagating microwaves, which distinguishes between radiation fields containing an even or odd number n of photons, both in a single-shot measurement and without perturbing the parity of the detected field. We showcase applications of the detector for direct Wigner tomography of propagating microwaves and heralded generation of Schr\"odinger cat states. This parity detection scheme is applicable over a broad frequency range and may prove useful, for example, for heralded or fault-tolerant quantum communication protocols.