Illustration: Virgo Observatory researchers are squeezing light

Source: H. Lück/B. Knispel/Max Planck Institute for Gravitational Physics

Physicists are reporting the results of a test designed to compress the vacuum within the universe to better detect the effects of colliding black holes.

Extreme extraterrestrial events, like two black holes or two supernovae colliding with each other, can create ripples in space called gravitational waves. On Earth, an observatory tried to detect these ripples using lasers, but because the effects of the waves are so subtle, even the randomness built into the vacuum affected the experiment's sensitivity. But the new method, developed over decades, has allowed researchers to reduce this interference and expand the range of gravitational wave detection.

Lisa Barsotti, a scientist and principal investigator at MIT's Kavli Institute for Astrophysics and Space Studies who works on LIGO, said: "The This method allows us to expand the scope of detecting gravitational waves."

Illustration: Gravitational wave model

Source: T. Pyle/Caltech/Massachusetts. Institute of Technology/Laser Interferometer Gravitational-Wave Observatory (LIGO) Laboratory

The Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo Gravitational-Wave Observatory rely on the principle of interference patterns generated by overlapping laser beams. The laser beam enters the optical element and is split into two beams. Each beam travels along two two-kilometer-long tubes to the mirror, where it is reflected by the mirror and recombined with the optical element. Light (even laser light) travels in waves, so when the beams come back together, they form a new wave. The passage of a gravitational wave slightly changes the distance traveled by one of the laser beams, and as the laser beams travel in and out of phase with each other, the signature of the laser beams is left on the corresponding final wave.

But after the laser is recombined, it must travel through quantum fluctuations within the vacuum of the machine. One conclusion of quantum mechanics, the theory that governs how subatomic particles interact, states that energy fluctuates in magnitude at the smallest scales. These fluctuations introduce a degree of uncertainty in the timing of light particles reaching the detector, which limits the detector's sensitivity because it is difficult to see changes in the phase of light presented by gravitational waves. Now, physicists have found a way to suppress those quantum fluctuations by introducing a "squeezed vacuum state" in the final step of the experiment.

One of the core principles of quantum mechanics is the Heisenberg Uncertainty Principle, which proposes that certain pairs of properties, such as the position, momentum or energy, and arrival time of a particle, cannot be accurately determined at the same time. Measurement. Increasing the precision of one value decreases the precision of the other, and vice versa. Compression is a way to increase the precision (and reduce noise) of values ??that are more interesting to physicists, at the expense of other values.

Illustration: The black line shows the amount of noise at a given frequency, without compression; the green line shows the effect of compression - less noise

Source: LIGO

< p> The workhorse of the noise suppression mechanism is a special crystal with tunable optical properties. The crystal links the laser beam passing through it to the energy fluctuations of the vacuum, allowing researchers to establish a new field in which they have transferred the noise of the property they are more interested in (the phase) to the one they are not. Then on the characteristic of interest (amplitude). They passed this light back to the output of the interferometer, where it replaced the noisy vacuum with a new compressed field, so that the final laser output was less noisy in phase and more noisy in amplitude. In order to reduce the noise caused by stray light in the crystal itself, the core component of the extruder is located in the LIGO vacuum device. In a paper published in Physical Review Letters, researchers report the successful application of this method in today's detectors of LIGO and the Virgo Gravitational Wave Observatory.

This is so important.

Ping Koy Lam, a professor of physics at the Australian National University who was not involved in the research but is working on experiments to compress space-time with gravitational wave detectors, told Astronomy Online in an email: "This result is a good demonstration that Learn how quantum technology can enhance precision instruments and push the boundaries of science.”

There’s no free lunch—amplitude noise appears elsewhere, leading to a slight increase in uncertainty about low-frequency gravitational waves. Nergis Mavalvala, a professor of astrophysics at MIT, told Astronomy Online that in the future, physicists hope to reduce the amplitude of low-frequency gravitational waves and increase the phase of high-frequency gravitational waves.

LIGO and the Virgo Gravitational-Wave Observatory are now using this compression method to increase sensitivity and continue to search for gravitational waves from colliding black holes. But for graduate student Maggie Tse, the paper's lead author, one of the most exciting things is seeing the otherwise elusive and difficult-to-measure world of quantum physics appear so often in real life. "It's amazing to be able to turn an elusive quantum state into something tangible," she told Astronomy Online.

Author: Ryan F. Mandelbaum

FY: Dancing Horse

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