Quantum localized modes in capacitively coupled Josephson junctions

TL;DR

This paper investigates quantum breather states in coupled Josephson junctions, demonstrating controllable tunneling of excitations via external bias, with implications for quantum information transfer.

Contribution

It reveals the existence of quantum breather states in coupled Josephson junctions and shows how their tunneling times can be controlled externally.

Findings

Quantum breather states exist in coupled Josephson junctions.

Tunneling times depend on initial excitation energy.

External bias can control excitation flow.

Abstract

We consider the quantum dynamics of excitations in a system of two capacitively coupled Josephson junctions. Quantum breather states are found in the middle of the energy spectrum of the confined nonescaping states of the system. They are characterized by a strong excitation of one junction. These states perform slow tunneling motion from one junction to the other, while keeping their coherent nature. The tunneling time sensitively depends on the initial excitation energy. By using an external bias as a control parameter, the tunneling time can be varied with respect to the escape time and the experimentally limited coherence time. Thus one can control the flow of quantum excitations between the two junctions.