Observation of the Unconventional Photon Blockade in the Microwave Domain

TL;DR

This paper reports the experimental observation of the unconventional photon blockade effect in microwave photons using coupled superconducting resonators, demonstrating nonclassical light with weak nonlinearity.

Contribution

First experimental demonstration of unconventional photon blockade in the microwave domain using superconducting resonators.

Findings

Measured $g^{(2)}(0)$ as low as 0.4 indicating nonclassical light

Observed oscillatory behavior of $g^{(2)}(t)$ confirming unconventional blockade

Achieved blockade with weakly nonlinear resonators

Abstract

We have observed the unconventional photon blockade effect for microwave photons using two coupled superconducting resonators. As opposed to the conventional blockade, only weakly nonlinear resonators are required. The blockade is revealed through measurements of the second order correlation function $g^{(2)}(t)$ of the microwave field inside one of the two resonators. The lowest measured value of $g^{(2)}(0)$ is 0.4 for a resonator population of approximately $10^{-2}$ photons. The time evolution of $g^{(2)}(t)$ exhibits an oscillatory behavior, which is characteristic of the unconventional photon blockade.