¶ Squeezer
A compressed light device has recently been added to the NSF's LIGO detectors and the European Virgo detector. A "squeezer's" function is to improve interferometer sensitivity by manipulating quantum fluctuations in the vacuum in which the instruments operate. These 'vacuum fluctuations' can alter the characteristics of individual photons and impair the accuracy with which gravitational wave detectors such as LIGO measure photon travel time through the sensor. Because changes in photon arrival times reveal the passage of a gravitational wave, precisely monitoring photon travel-time via the sensor is critical to achieving a discovery. By improving this measurement using the squeezer, LIGO and Virgo will become more sensitive.
FIG. 1: (a) High-level schematic of the Advanced LIGO squeezer subsystem injection into the main interferometer. Control sidebands are imprinted onto the squeezer laser using acousto-/electro-optic modulators (A/EOMs). These sidebands are used to attain phase stability of the second harmonic generator (SHG)—used to generate the green pump field—and the optical parametric oscillator (OPO), which produces the squeezed vacuum state.Thermoelectric coolers keep each crystal at a steady temperature. Steering mirrors (ZM1 and ZM2) direct the squeezed vacuum into the interferometer. Gray lines trace paths from readbacks from the squeezer feedback loops and representative witness sensors to the input of the machine learning model. Included among these auxiliary channels are data produced by photodiodes (both power measurements and alignment error signals), seismometers and thermistors. (b) The network is comprised of a series of hidden dense layers with which it calculates an estimate of the squeezing level observed in the interferometer. The full list of channels used as input is given in Table I. (c) A time series of the squeezing level observed throughout O3, measured using the cross correlation of the interferometer readout photodiodes, also plotted as a histogram. The dashed line denotes the mean squeezing level of 2.23 dB throughout the run.
¶ Channel Name Breakdown:
| Name | Description |
|---|---|
| Channels | |
| SQZ | Squeezer |
¶ Sources
https://physics.aps.org/articles/v12/139
https://arxiv.org/pdf/2305.13780.pdf