Single Cooper pair tunneling induced by non-classical microwaves

TL;DR

This paper investigates how non-classical microwave states, especially squeezed vacuum, influence Cooper pair tunneling in a Josephson junction, revealing unique tunneling phenomena and modified Bloch steps.

Contribution

It demonstrates that non-classical microwaves can induce single Cooper pair tunneling and significantly alter Josephson junction dynamics, a novel insight into quantum microwave interactions.

Findings

Bloch steps observed with squeezed vacuum microwaves

Interval between Bloch steps doubles compared to classical case

Non-classical microwaves enable tunneling with zero average field

Abstract

A mesoscopic Josephson junction interacting with a mode of non-classical microwaves with frequency $\omega$ is considered. Squeezing of the electromagnetic field drastically affects the dynamics of Cooper tunneling. In particular, Bloch steps can be observed even when the microwaves are in the squeezed vacuum state with {\em zero} average amplitude of the field $\langle E(t) \rangle = 0$. The interval between these steps is double in size in comparison to the conventional Bloch steps.