Location: ERC 426
Scientific Advisor: Stephan S. Meyer
Ph.D. Thesis Defense
Defense date: June 22, 2016
Experimental Constraints on the Exotic Shearing of Space-Time"
Ph.D. Advisor: Stephan S. Meyer
Ph.D. Committee members: Craig Hogan, Daniel Holz, Edward Kibblewhite, Stephan S. Meyer
"Jon's thesis represents an important milestone. He's done much of the critical work to make the Holometer experiment a reality. It's the most sensitive instrument ever built to study tiny random jitters of space. In his thesis, he shows that the scale of random shear jitter is more than an order of magnitude less than the Planck length, which was the theoretical expectation. The experiment essentially rules out this effect. He's working with our team now to reconfigure the machine to study the other possibility, a jitter of rotational motion, at similar sensitivity. There is some hope that this effect in the laboratory may connect with the cosmic dark energy problem."
- Craig J. Hogan
Thesis Abstract: The Holometer program is a search for first experimental evidence that space-time has quantum structure. The detector consists of a pair of co-located 40-m power-recycled interferometers whose outputs are read out synchronously at 50 MHz, achieving sensitivity to spatially-correlated fluctuations in differential position on time scales shorter than the light-crossing time of the instruments. Unlike gravitational wave interferometers, which time-resolve transient geometrical disturbances in the spatial background, the Holometer is searching for a universal, stationary quantization noise of the background itself.
This dissertation presents the final results of the Holometer Phase I search, an experiment configured for sensitivity to exotic coherent shearing fluctuations of space-time. Measurements of high-frequency cross-spectra of the interferometer signals obtain sensitivity to spatially-correlated effects far exceeding any previous measurement, in a broad frequency band extending to 7.6~MHz, twice the inverse light-crossing time of the apparatus. This measurement is the statistical aggregation of 2.1 petabytes of 2-byte differential position measurements obtained over a month-long exposure time. At 3-sigma significance, it places an upper limit on the coherence scale of spatial shear two orders of magnitude below the Planck length.
The result demonstrates the viability of this novel spatially-correlated interferometric detection technique to reach unprecedented sensitivity to coherent deviations of space-time from classicality, opening the door for direct experimental tests of theories of relational quantum gravity.
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