Quantum-classical crossover of a field mode

Abstract

We explore the quantum-classical crossover in the behavior of a quantum field mode. The quantum behavior 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 behavior of the field and continuous Rabi oscillations form the signature for classical behavior of the field. We demonstrate both limits in a single model for the full coupled system, for field states with the same average field strength, and so for qubits with the same Rabi frequency.