Photodetection of propagating quantum microwaves in circuit QED

TL;DR

This paper presents a theoretical design for a high-efficiency microwave photon detector using an array of superconducting nanocircuits in a circuit QED setup, enabling potential advances in quantum information processing with propagating microwaves.

Contribution

It introduces a formal quantum field theory model for a metamaterial microwave photon detector with superconducting qubits, analyzing its efficiency and feasibility for experimental realization.

Findings

Single-photon absorption efficiency evaluated for various absorber configurations

Design based on superconducting phase qubits in a coplanar waveguide

Potential for implementing all-optical quantum information processing

Abstract

We develop the theory of a metamaterial composed of an array of discrete quantum absorbers inside a one-dimensional waveguide that implements a high-efficiency microwave photon detector. A basic design consists of a few metastable superconducting nanocircuits spread inside and coupled to a one-dimensional waveguide in a circuit QED setup. The arrival of a {\it propagating} quantum microwave field induces an irreversible change in the population of the internal levels of the absorbers, due to a selective absorption of photon excitations. This design is studied using a formal but simple quantum field theory, which allows us to evaluate the single-photon absorption efficiency for one and many absorber setups. As an example, we consider a particular design that combines a coplanar coaxial waveguide with superconducting phase qubits, a natural but not exclusive playground for experimental implementations. This work and a possible experimental realization may stimulate the possible arrival of "all-optical" quantum information processing with propagating quantum microwaves, where a microwave photodetector could play a key role.