Cavity QED at the quantum-classical boundary

J. M. Raimond

Charlotte Lemoine

We propose an organizational principle for the classical-quantum boundary that focuses on the conditions under which non-classical effects become operationally manifest and experimentally certifiable. Standard decoherence theory explains why quantum signatures become latent in generic environments; we complement this by making explicit the physical conditions that render quantum manifestation robust. Building on Haroche's cavity-QED experiments as a paradigmatic case, we show that measurable mode properties — frequencies, lifetimes, and couplings — depend on boundary conditions, environment, and preparation-measurement protocols. We formalize this through the framework (Ω, C, Ω_eff(C), W, W*(C)), where Ω denotes a reservoir of dynamical degrees of freedom, C the physical and protocol conditions, Ω_eff(C) the context-induced effective modal structure, W a quantum witness, and W*(C) a context-dependent certifiability threshold. A quantum effect is manifest when W(C) > W*(C). We illustrate this principle with cavity QED, the Casimir effect, and atomic clocks. The framework reformulates the classical-quantum boundary as a boundary of conditional manifestability rather than a dichotomy between system types.

Jonathan P. Dowling

Matthew Bradford, Jung‐Tsung Shen

We investigate the effects of a nanophotonic boundary on the spontaneous emission properties of an excited two-level atom in cavity quantum electrodynamics (QED) geometry. We show that a boundary provides temporally delayed interference, which can be either constructive or destructive. Consequently, the decay of the atomic excitation can be either increased or greatly inhibited. As a concrete example, we investigate the spontaneous emission process in cavity QED with a terminated line-defect waveguide, and show the rich behavior of the atomic response due to the boundary. We also show that the output photonic wave form is strongly influenced by the boundary.

Pascal Degiovanni, Valentin Bonzom, Hichem Bouzidi +4 more

S. Haroche, J. M. Raimond