Single-Photon Signal Sideband Detection for High-Power Michelson Interferometers

The Michelson interferometer is a cornerstone of experimental physics. Its applications range from providing first impressions of wave interference in educational settings to probing spacetime at minuscule precision scales. Interferometer precision provides a unique view of the fundamental medium of matter and energy, enabling tests for new physics as well as searches for the gravitational wave signatures of distant astrophysical events. Optical interferometers are typically operated by continuously measuring the power at their output port. Signal perturbations then create sideband fields, forming a beat-note with the fringe light that modulates that power. When operated at a nearly-dark destructive interference fringe, this readout is a form of homodyne detection, with an imprecision set by a ``standard quantum limit'' attributed to shot noise from quantum vacuum fluctuations. The sideband signal fields carry energy which can, alternatively, be directly observed as photons distinct from the source laser. Without signal energy, vacuum does not form sidebands and cannot spuriously create photon counts or shot noise. Thus, counting can offer improved statistics when searching for weak signals when classical backgrounds are below the standard quantum limit. Here, photon counting statistics are described for optical interferometry, relating the two forms of measurement and showing cases where counting greatly outperforms homodyne readout, even with squeezed state quantum enhancement. The most immediate application for photon counting is improving searches of stochastic signals, such as from quantum gravity or from new particle fields. The advantages of counting may extend to wider applications, such as gravitational wave detectors, and the concept of Fisher-information representative spectral density is introduced to motivate further study.Comment: 34 pages, 6 figure

J.B. McCuller to Sir, December 1963

Personal correspondenc

The influence of abiotic and biotic factors on two nudibranchs feeding upon Membranipora membranacea in the southern Gulf of Maine

The abiotic (temperature and flow rate) and biotic factors within fouling communities at three marinas located along the southern Gulf of Maine from June to December in 2010 and 2011 were surveyed. The goal of this study was to determine what is driving the recent population increase of the nudibranch, Corambe obscura, and whether the native nudibranch, Onchidoris muricata, is transitioning prey species. In addition, the affects of temperature on aspects of C. obscura\u27s life history were determined by laboratory experiments. Results suggest that abiotic factors influence basic community members such as the kelp host, Saccharina latissima, and the invasive bryozoan, Membranipora membranacea, biotic factors such as settlement substrate and prey species are more important to the predatory nudibranchs. Consequently, while C. obscura\u27s presence would not be possible without the presence of M. membranacea, temperature has allowed them to have high turnover rates and reproduction which increases their population size

Terrestrial Vertebrates of Fannin County, Texas

The purposes of this thesis were (1) to provide some knowledge of the herptiles and mammals of this area, (2) to clarify the distribution of many of these animals in this section of Texas, and (3) to provide additional ecological information about the area

Using Relational Frame Theory to Teach Nutritional Values

Obesity is a significant health concern people of all ages on a global level. There have many studies that addressed nutrition concepts, however, those results are inadequate to lead to long term improved health because the improvements were too weak, too short lived, or did not generalize to other environments. There is a need to enhance the educational component and one solution is to design the instructional component using a theory of language and cognition, Relational Frame Theory (RFT). This method not only has potential to help the student learn information about foods, but also learn how to make comparisons between foods. This study implemented a nutritional education program using a relational frame theory format to teach nutritional relations using the relational frame, “healthier,” and assessed for derived relations. The first step involved teaching equivalence relations between nine foods categorized into three groups, maximum nutritional value, moderate nutritional value, and minimal nutritional value. After the initial equivalence training and remediation procedures all the participants demonstrated mastery on equivalence relations that were taught and derived. Next, participants were taught two comparison relations and assessed for comparison relations that were taught and derived. Of the comparison relations assessed, two of the participants improved their performance in the comparison relations that were taught

First measurements of high frequency cross-spectra from a pair of large Michelson interferometers

Measurements are reported of the cross-correlation of spectra of differential position signals from the Fermilab Holometer, a pair of co-located 39 m long, high power Michelson interferometers with flat, broadband frequency response in the MHz range. The instrument obtains sensitivity to high frequency correlated signals far exceeding any previous measurement in a broad frequency band extending beyond the 3.8 MHz inverse light crossing time of the apparatus. The dominant but uncorrelated shot noise is averaged down over $2\times 10^8$ independent spectral measurements with 381 Hz frequency resolution to obtain $2.1\times 10^{-20} \ \mathrm{m}/\sqrt{\mathrm{Hz}}$ sensitivity to stationary signals. For signal bandwidths $\Delta f > 11$ kHz, the sensitivity to strain $h$ or shear power spectral density of classical or exotic origin surpasses a milestone $PSD_{\delta h} < t_p$ where $t_p= 5.39\times 10^{-44}/\mathrm{Hz}$ is the Planck time.Comment: 5 pages, 3 figure

Interferometric Constraints on Quantum Geometrical Shear Noise Correlations

Final measurements and analysis are reported from the first-generation Holometer, the first instrument capable of measuring correlated variations in space-time position at strain noise power spectral densities smaller than a Planck time. The apparatus consists of two co-located, but independent and isolated, 40 m power-recycled Michelson interferometers, whose outputs are cross-correlated to 25 MHz. The data are sensitive to correlations of differential position across the apparatus over a broad band of frequencies up to and exceeding the inverse light crossing time, 7.6 MHz. By measuring with Planck precision the correlation of position variations at spacelike separations, the Holometer searches for faint, irreducible correlated position noise backgrounds predicted by some models of quantum space-time geometry. The first-generation optical layout is sensitive to quantum geometrical noise correlations with shear symmetry---those that can be interpreted as a fundamental noncommutativity of space-time position in orthogonal directions. General experimental constraints are placed on parameters of a set of models of spatial shear noise correlations, with a sensitivity that exceeds the Planck-scale holographic information bound on position states by a large factor. This result significantly extends the upper limits placed on models of directional noncommutativity by currently operating gravitational wave observatories.Comment: Matches the journal accepted versio

Frequency-Dependent Squeezing for Advanced LIGO

The first detection of gravitational waves by the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015 launched the era of gravitational wave astronomy. The quest for gravitational wave signals from objects that are fainter or farther away impels technological advances to realize ever more sensitive detectors. Since 2019, one advanced technique, the injection of squeezed states of light is being used to improve the shot noise limit to the sensitivity of the Advanced LIGO detectors, at frequencies above $\sim 50$ Hz. Below this frequency, quantum back action, in the form of radiation pressure induced motion of the mirrors, degrades the sensitivity. To simultaneously reduce shot noise at high frequencies and quantum radiation pressure noise at low frequencies requires a quantum noise filter cavity with low optical losses to rotate the squeezed quadrature as a function of frequency. We report on the observation of frequency-dependent squeezed quadrature rotation with rotation frequency of 30Hz, using a 16m long filter cavity. A novel control scheme is developed for this frequency-dependent squeezed vacuum source, and the results presented here demonstrate that a low-loss filter cavity can achieve the squeezed quadrature rotation necessary for the next planned upgrade to Advanced LIGO, known as "A+."Comment: 6 pages, 2 figures, to be published in Phys. Rev. Let