The quantum-classical crossover of a field mode

TL;DR

This paper investigates the transition between quantum and classical behavior in a field mode by analyzing a coupled qubit-field system, identifying signatures of each regime through collapse, revival, and Rabi oscillations.

Contribution

It presents a unified model demonstrating both quantum and classical signatures in a coupled system with the same average field strength.

Findings

Collapse and revival indicate quantum behavior.

Continuous Rabi oscillations indicate classical behavior.

Both regimes are demonstrated within a single model.

Abstract

We explore the quantum-classical crossover in the behaviour of a quantum field mode. The quantum behaviour of a two-state system - a qubit - coupled to the field is used as a probe. Collapse and revival of the qubit inversion form the signature for quantum behaviour of the field and continuous Rabi oscillations form the signature for classical behaviour of the field. We demonstrate both limits in a single model for the full coupled system, for states with the same average field strength, and so for qubits with the same Rabi frequency.