Since the historical finding of gravitational waves from two black holes colliding over one billion light-years away, 201
LSU Department of Physics & Astronomy Associate Professor Thomas Corbitt and his research group now present the first broadband measurement of quantum radiation pressure noise in the audio band at frequencies relevant to gravity wave detectors, as reported today in the scientific journal Nature . The research was supported by the National Science Foundation or NSF, and the findings hint at methods to improve the sensitivity of gravity wave detectors by developing techniques to mitigate the inaccuracy of back-action measurements, thereby increasing the chances of detecting gravity waves.
Corbitt and researchers have developed physical devices that allow to observe and hear quantum effects at room temperature. It is often easier to measure quantum effects at very cold temperatures, while this approach brings them closer to human experience. Built-in miniature models of detectors such as LIGO or Laser Interferometer Gravitational Wave Observatory located in Livingston, La. And Hanford, Wash., These units consist of low-tablet, single-crystalline microresonators – each a small mirror cushion the size of a pin dot suspended from a cantilever. A laser beam is directed at one of these mirrors, and when the beam is reflected, the oscillating beam pressure is enough to bend the edgeless structure, causing the mirror to vibrate, causing noise.
Gravitational wave interferometers use as much laser power as possible to minimize the uncertainty caused by the measurement of discrete photons and to maximize the signal-to-noise ratio. These higher power beams increase position accuracy, but also increase the backlash, which is the uncertainty in the number of photons reflecting a mirror corresponding to a swinging force due to the beam pressure on the mirror, causing mechanical movement. Other types of noise, such as Thermal noise usually dominates over nitrogen radiation noise, but Corbitt and his team, including partners at MIT, have sorted through them. Advanced LIGO and other second and third generation interferometers will be limited by low frequency quantum radiation noise when running at their full laser power. Corbit's paper in Nature provides traces of how scientists can work around this by measuring gravitational waves.
"Given the importance of more sensitive gravitational wave detectors, it is important to study the effects of quantum radiation noise in a system similar to advanced LIGO, which will be limited by quantum radiation pressure across a wide range of frequencies far from the mechanical resonance frequency of the test mass suspension. ", says Corbitt.
Corbit's former academic advisor and lead author of Nature paper, Jonathan Cripe, educated from LSU with a Ph.D. in physics last year and is now a postdoctoral researcher at the National Institute of Standards and Technology:
"Day-to-day at LSU, when I did the background work on designing this experiment and micro-mirrors and placing all the opticians on the table, I didn't really think about the effects of the future," cripe said. "I just focused on each step and took things one day at a time. [But] Now that we've done the experiment, it's really great to go back and think about the fact that quantum mechanics – something that works foreign and removed from the daily human experience – is the main driver of a mirror's movement visible to the human eye. The quantum vacuum or & nbsp; nothing can affect anything you can see. "
Pedro Marronetti, a physicist and The NSF program director notes that it may be difficult to test new ideas for improving gravitational wave detectors, especially when reducing noise measured only in a full-scale interferometer:
"This breakthrough opens up new possibilities for testing noise reduction," he said. The relative simplicity of the approach makes it available to a wide range of research groups that potentially increase the participation of the wider scientific community in gravitational wave astrophysics. "
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Jonathan Cripe et al., Measurement of quantum reaction in the sound band at room temperature, Nature (2019). DOI: 10,1038 / s41586-019-1051-4