LIGO Document T1800296-v1

Constructing a Balanced Homodyne Detector for Low Quantum Noise Gravitational Wave Interferometry

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T - Technical notes
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Achieving more efficient detection of gravitational radiation is a goal of contemporary experimental physics,
as it will enable novel tests of general relativity and provide information on astronomical bodies that are
difficult to observe through the electromagnetic spectrum. However, as gravitational wave interferometers
increase their sensitivity, sources of quantum noise dominate over classical noise sources. Further reduction
of noise requires gravitational wave observatories to use non-classical, squeezed states of light, in which the
quantum noise of one quadrature is decreased while that of another is increased. A balanced homodyne
detector can measure an arbitrary quadrature of light by mixing a weak signal with a strong source of light.
This technique can be incorporated into interferometers to perform precise measurements using squeezed
light. Since these highly quantum states are crucial to gravitational wave physics, numerous research labs
seek to perform experiments with these detectors. The goal of this project is to construct the optical
components and readout electronics for a balanced homodyne detector that may be used in various LIGO
research labs performing experiments with non-classical light.
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