Definition of Coherence

良昌 村山, 正樹 本田

Pierre Vernotte

Jan Peřina, Ladislav Mišta

Definitions of the coherence time, coherence area and coherence volume are proposed for superposed coherent and chaotic radiation, such as laser radiation above the threshold, on the basis of the photon statistics of the radiation. Such definitions may contribute to a unified judgment of the coherence properties of the radiation in any order, while the definitions usually used are connected with interferometric measurements of the second-order coherence properties. A close relationship to the definitions proposed earlier in the literature for chaotic radiation is shown.

H. D. Zeh

Andreas Albrecht

There are many striking phenomena which are attributed to ‘quantum coherence’. It is natural to wonder if there are new quantum coherence effects waiting to be discovered which could lead to interesting results and perhaps even practical applications. A useful starting point for such discussions is a definition of ‘quantum coherence’. In this article I give a definition of quantum coherence and use a number of illustrations to explore the implications of this definition. I point to topics of current interest in the fields of cosmology and quantum computation where questions of quantum coherence arise, and I emphasize the impact that interactions with the environment can have on quantum coherence.

Andreas Albrecht

There are many striking phenomena which are attributed to "quantum coherence". It is natural to wonder if there are new quantum coherence effects waiting to be discovered which could lead to interesting results and perhaps even practical applications. A useful starting point for such discussions is a definition of "quantum coherence". In this article I give a definition of quantum coherence and use a number of illustrations to explore the implications of this definition. I point to topics of current interest in the fields of cosmology and quantum computation where questions of quantum coherence arise, and I emphasize the impact that interactions with the environment can have on quantum coherence.