Quantum Optics in Astrophysics: The Potential of a New Window

The entire optical astronomy relies upon the detection of light. In this contribution, we put emphasis to the fact that a new window to the universe could be opened with the obvious idea of applying the Quantum Theory to describe incoming light Quanta (!). It is clearly the appropriate approach but, nevertheless, it never deemed necessary in main stream astrophysics: Customarily, traditional astronomy not only prefers time-averaged quantities, (although fluctuations in time of a measurement can be a source of information which is getting entirely lost in any time-averaged value) but misses much more information content by continuing to use old semi-classical approaches to treat photon detection processes. Thus, we fail to describe and appreciate in full very important properties of cosmic light, like spatiotemporal coherence. Nevertheless, 45 years of knowledge accumulation in Quantum Optics and technology can now result to the development of instruments capable to extract intimate quantum information scrambled in the incoming optical light fields from celestial sources, provided their ability to detect light emission alterations in the < ns timescales, can be demonstrated. In the emerging field of Quantum or 'Photonic' Astrophysics (QAp) random fluctuations of light are not considered undesirable as unavoidable photon-noise that hampers the photometrical precision, but, instead, as a subject of investigation per se. Such light fluctuations can frequently be valuable as a rich source of information. Statistical fluctuations, are able to provide radically new diagnostic methods of physical conditions in astrophysical plasmas by directly identifying characteristic quantum signatures of light-generating or light-scattering processes. However, it has to be noted that, close enough to the quantum limit, the bosonic character of photon cannot be ignored and, therefore, a detailed Quantum Electrodynamical treatment of the interaction of the incoming photon stream with every component comprising the chain of physical systems from the source to the detecting instrument, has to be elaborated. To propagate the main ideas regarding the framework of QAp is not an easy task. Here, summarize the conceptual foundations and experimental aspects of such a new information channel and then describe the main strategy aspects, to develop the subject. We discuss also, briefly, the scientific rationale, prospects and difficulties of the above mentioned instruments and describe th