On September 14th, 2015, the two laser interferometers of LIGO, the Laser Interferometric Gravitational-Wave Observatory, made the first direct detection of gravitational waves. The signal came from the coalescence of two black holes, and while the event released an incredible 3 solar masses of energy in gravitational waves, it produced a peak strain signal of only 10^-21 in the LIGO detectors. To measure this incredibly small strain, the LIGO interferometers had to perform the most sensitive displacement measurements ever made. This talk will focus on the science of the detectors: the special interferometry techniques used to split the fringe to a part in a billion; the technical and fundamental limits to detector sensitivity, including thermal and quantum fluctuations; and how squeezed light is being used to further reduce quantum noise.

Dr. Peter Fritschel is a Senior Research Scientist in the Kavli Institute for Astrophysics and Space Research at M.I.T. He received his B.S. (1984) in physics from Swarthmore College, and his Ph.D. (1992) in physics from M.I.T., working on developing the techniques for gravitational wave detection using interferometry. From 1992-1993, he worked in the French-Italian gravitational wave detector project Virgo, in Orsay, France. Dr. Fritschel returned to M.I.T. as a research scientist in 1993 to work on LIGO, the Laser Interferometric Gravitational-wave Observatory. He is currently Chief Detector Scientist for the LIGO Laboratory, and Associate Director for LIGO MIT.

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