Quantum gravito-optics: a light route from semiclassical gravity to quantum gravity. (2nd July 2015)

• Record Type: Journal Article
• Authors: Unnikrishnan, C S; Gillies, George T
• Is Part Of: Classical and quantum gravity. Volume 32:Number 14(2015:Jul.)
• Publication Date: 2015-07-02
• Subjects: gravitation waves -- gravitational atom -- coherent state -- quantum gravity; Quantum gravity -- Periodicals; Gravitation -- Periodicals; Relativity (Physics) -- Periodicals; Space and time -- Periodicals; Periodicals; 521.1
• DOI: 10.1088/0264-9381/32/14/145012
• Languages: English
• ISSNs: 0264-9381

Abstract

Abstract: Quantum gravity remains an elusive theory, in spite of our thorough understanding of the quantum theory and the general theory of relativity separately, presumably due to the lack of any observational clues. We argue that the theory of quantum gravity has a strong constraining anchor in the sector of gravitational radiation, ensuring reliable physical clues, albeit in a limited observable form. In particular, all types of gravitational waves expected to be observable in LIGO-like advanced detectors are fully quantum mechanical states of radiation. Exact equivalence of the full quantum gravity theory with the familiar semiclassical theory is ensured in the radiation sector, in most real situations where the relevant quantum operator functions are normal ordered, by the analogue of the optical equivalence theorem in quantum optics. We show that this is indeed the case for the detection of the waves from a massive binary system, a single gravitational atom, that emits coherent radiation. The idea of quantum-gravitational optics can assist in guiding along the fuzzy roads to quantum gravity.