Exploiting Kerr Cross Non-linearity in Circuit Quantum Electrodynamics for Non-demolition Measurements

TL;DR

This paper introduces a new method for quantum non-demolition measurement of photon number states using Kerr cross non-linearity in superconducting microwave resonators, with experimental validation.

Contribution

It proposes a dispersive readout scheme leveraging Kerr non-linearity for non-demolition measurements and demonstrates experimental proof-of-concept data.

Findings

Scheme operates at single photon level

Enhanced responsivity through symmetry design

Experimental demonstration of principle

Abstract

We propose a scheme for dispersive readout of stored energy in one mode of a nonlinear superconducting microwave ring resonator by detection of the frequency shift of a second mode coupled to the first via a Kerr nonlinearity. Symmetry is used to enhance the device responsivity while minimizing self nonlinearity of each mode. Assessment of the signal to noise ratio indicates that the scheme will function at the single photon level, allowing quantum non-demolition measurement of the photon number state of one mode. Experimental data from a simplified version of the device demonstrating the principle of operation are presented.