Cooperative effects in Josephson junctions in a cavity in the strong coupling regime

TL;DR

This paper investigates the collective quantum dynamics of multiple Josephson junction qubits in a cavity under strong coupling, revealing Rabi oscillations with Bessel function dependence and proposing a quantum amplifier design.

Contribution

It extends the analysis of Josephson junction qubits in a cavity to multi-qubit systems and introduces a new selection rule for Rabi oscillations in the strong coupling regime.

Findings

Rabi oscillations exhibit frequencies proportional to integer order Bessel functions.

A selection rule governs the occurrence of Rabi oscillations.

A quantum amplifier concept using many Josephson junctions is proposed.

Abstract

We analyze the behavior of systems of two and three qubits made by Josephson junctions, treated in the two level approximation, driven by a radiation mode in a cavity. The regime we consider is a strong coupling one recently experimentally reached for a single junction. Rabi oscillations are obtained with the frequency proportional to integer order Bessel functions in the limit of a large photon number, similarly to the case of the single qubit. A selection rule is derived for the appearance of Rabi oscillations. A quantum amplifier built with a large number of Josephson junctions in a cavity in the strong coupling regime is also described.