This thesis has two basic themes: the investigation of new experimentswhich can be used to test relativistic gravity, and the investigation of newtechnologies and new experimental techniques which can be applied to makegravitational wave astronomy a reality.
Advancing technology will soon make possible a new class of gravitationexperiments: pure laboratory experiments with laboratory sources of non-Newtoniangravity and laboratory detectors. The key advance in techno1ogyis the development of resonant sensing systems with very low levels of dissipation.Chapter 1 considers three such systems (torque balances, dielectricmonocrystals, and superconducting microwave resonators), and it proposeseight laboratory experiments which use these systems as detectors. For eachexperiment it describes the dominant sources of noise and the technologyrequired.
The coupled electro-mechanical system consisting of a microwave cavityand its walls can serve as a gravitational radiation detector. A gravitational wave interacts with the walls, and the resulting motion inducestransitions from a highly excited cavity mode to a nearly unexcited mode.Chapter 2 describes briefly a formalism for analyzing such a detector, andit proposes a particular design.
The monitoring of a quantum mechanical harmonic oscillator on which aclassical force acts is important in a variety of high-precision experiments,such as the attempt to detect gravitational radiation. Chapter 3 reviewsthe standard techniques for monitoring the oscillator; and it introduces anew technique which, in principle, can determine the details of the forcewith arbitrary accuracy, despite the quantum properties of the oscillator.
The standard method for monitoring the oscillator is the "amplitude-and-phase" method (position or momentum transducer with output fed througha linear amplifier). The accuracy obtainable by this method is limited bythe uncertainty principle. To do better requires a measurement of the typewhich Braginsky has called "quantum nondemolition." A well-known quantumnondemolition technique is "quantum counting," which can detect an arbitrarilyweak force, but which cannot provide good accuracy in determiningits precise time-dependence. Chapter 3 considers extensively a new typeof quantum nondemolition measurement - a "back-action-evading" measurementof the real part X1 (or the imaginary part X2) of the oscillator's complexamplitude. In principle X1 can be measured arbitrarily quickly and arbitrarilyaccurately, and a sequence of such measurements can lead to anarbitrarily accurate monitoring of the classical force.
Chapter 3 describes explicit gedanken experiments which demonstrate thatX1 can be measured arbitrarily quickly and arbitrarily accurately, it considersapproximate back-action-evading measurements, and it develops a theoryof quantum nondemolition measurement for arbitrary quantum mechanical systems.
In Rosen's "bimetric" theory of gravity the (local) speed of gravitationalradiation vg is determined by the combined effects of cosmologicalboundary values and nearby concentrations of matter. It is possible for vgto be less than the speed of light. Chapter 4 shows that emission of gravitationalradiation prevents particles of nonzero rest mass from exceeding thespeed of gravitational radiation. Observations of relativistic particlesplace limits on vg and the cosmological boundary values today, and observationsof synchrotron radiation from compact radio sources place limits onthe cosmological boundary values in the past.
