coherencedomain

Coherencedomain is a term used in physics and information theory to denote a region or subspace in which the phase relationships between constituent elements remain sufficiently well defined to support coherent behavior. The phrase is not universally standardized and is used in several different contexts, emphasizing either wave-based coherence or quantum coherence depending on the field.

In wave physics, a coherencedomain can be described using the mutual or complex degree of coherence, γ(r1, r2, t), computed from the cross-spectral density of the field. The coherencedomain is conceptually the largest set of points among which |γ(r1, r2, t)| remains above a chosen threshold, or, practically, the region where interference visibility exceeds a specified level. This leads to related quantities such as coherence length and coherence time, which bound the spatial or temporal extent of coherence within the domain.

In quantum information and condensed-matter contexts, a coherencedomain may refer to a subspace of the system's Hilbert space where off-diagonal density-matrix elements are sizeable, allowing superpositions, interference, and, in some cases, entanglement. Here, decoherence processes define boundaries of the domain because environmental interactions reduce coherence outside it.

Applications include precision interferometry, holography, optical communications, and the design of quantum devices where maintaining coherence in a controllable domain is essential. The concept helps describe how coherence propagates, is preserved, or decays in complex media, materials, or circuits.

See also: coherence, coherence length, mutual coherence function, decoherence, density matrix, interferometry.