# Looking back on the laser of Schawlow and Townes, and looking forwards to the generation of gravitational radiation.

Abstract:

In their historic 1958 paper, Schawlow and Townes proposed the use of stimulated emission for generating macroscopically coherent light.  Here it is proposed that the use of charged, macroscopically coherent quantum matter can lead to the efficient generation of gravitational waves by means of transduction from electromagnetic waves.

The interaction of charged, macroscopically coherent quantum systems, such as a pair of charged superconducting spheres, with both electromagnetic (EM) and gravitational (GR) waves, will be considered. When the charge-to-mass ratio of a pair of identical, levitated superconducting spheres is adjusted so as to satisfy the "criticality" condition $Q/M=\sqrt{4{\pi}{\epsilon_{0}}G}$, where $\epsilon_{0}$ is the permittivity of free space, and $G$ is Newton's gravitational constant, the gravitational force of attraction will be balanced against the electrostatic force of repulsion between the two spheres, which are freely floating in space.  At criticality, when these two spheres are set in simple harmonic motion relative to each other by, say, a passing GR wave, they will radiate equal amounts of quadrupolar GR and EM radiation.  The superconducting spheres possess an energy gap (the BCS gap) separating the ground state from all excited states.  At sufficiently low temperatures with respect to the BCS gap, all dissipative degrees of freedom of the spheres will be frozen out by the Boltzmann factor.  Then at criticality, there will be an equipartition of both kinds of incident radiation upon scattering.  This implies that a Hertz-like experiment, i.e., a GR transmitter-receiver experiment, should be experimentally feasible.  I will present theoretical and experimental progress on this problem.

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