A tiny crystal device could amplify gravitational wave detectors to detect the cries of the birth of black holes

(MENAFN – Conversation) In 2017, astronomers witnessed the birth of a black hole for the first time. Gravitational wave detectors picked up the ripple in space that caused two neutron stars to collide to create a black hole, and other telescopes then observed the resulting explosion.

But the actual smoothness of how the black hole formed, the movements of matter in the moments before it was sealed within the event horizon of the black hole, went unnoticed. This is because the gravitational waves ejected at these last moments had such a high frequency that our current detectors could not pick them up.

Read more: We finally found gravitational waves from a pair of collapsing neutron stars

If you could watch ordinary matter turning into a black hole, you would see something like the Big Bang played backwards. Scientists designing gravitational wave detectors have worked hard to figure out how to improve our detectors to make this possible.

Today, our team is publishing work that shows how this can be done. Our proposal could make detectors 40 times more sensitive to the high frequencies we need, allowing astronomers to listen to the matter that creates a black hole.

It involves the creation of strange new energy packets (or “quanta”) that are a combination of two types of quantum vibrations. Devices based on this technology can be added to existing gravity wave detectors to gain additional sensitivity.

The artist’s conception of a photon in interaction with a millimeter-range phonon crystal device located in the output stage of a gravity wave detector. Carl Knox / OzGrav / Swinburne University, author Quantum problems

Gravitational wave detectors such as the Laser Interferometer Gravitational-wave Observatory (LIGO) in the United States use lasers to measure incredibly small changes in the distance between two mirrors. Because they measure changes 1000 times smaller than the size of a single proton, the effects of quantum mechanics – single particle physics or quantum energy – play an important role in the way these detectors work.

Two different types of quantum energy packages are involved, both predicted by Albert Einstein. In 1905, he predicted that light would come in energy packets we call photons; two years later, he predicted that thermal and sound energy would come in energy packets called phonons.

Photons are widely used in modern technology, but phonons are much harder to use. Individual phonons are usually flooded with a large number of random phonons that represent the heat of their surroundings. In gravitational wave detectors, phonons are reflected inside the detector mirror, worsening their sensitivity.

Read more: Australia’s share of global gravitational wave detection efforts

Five years ago, physicists realized that the problem of insufficient sensitivity at high frequency can be solved with devices that combine phonons and photons. They have shown that devices in which energy is transferred in quantum packets that share the properties of both phonons and photons can have rather remarkable properties.

These devices would involve a radical change in a well-known concept called “resonant amplification”. Resonant boost is what you do when you press the swing on the court: if you press at the right time, all your small inclines create a big swing.

The new device, called the “white light cavity”, would amplify all frequencies equally. This is like a swing with which you could push any old time and still achieve great results.

However, no one has yet figured out how to make one of these devices, because the phonons in it would be flooded with random vibrations caused by heat.

Quantum solutions

In our paper, published in Communications Physics, we show how two different projects currently underway could do the job.

The Niels Bohr Institute in Copenhagen is developing devices called background crystals, in which thermal vibrations are controlled by a crystal-like structure cut into a thin membrane. The Australian Center of Excellence for Designed Quantum Systems has also demonstrated an alternative system in which phonons are trapped in an ultrapure quartz lens.

The artist’s impression of a small device that can increase the sensitivity of a gravity wave detector at high frequencies. Carl Knox / OzGrav / Swinburne University, author

We show that both of these systems meet the requirements for creating the “negative dispersion” – which propagates the frequencies of light in the inverse form of the rainbow – required for white light cavities.

Both systems, when added to the rear end of existing gravitational wave detectors, would improve sensitivity at frequencies of a few kilohertz by 40 times or more times needed to listen to the birth of a black hole.

What’s next?

Our research does not represent an immediate solution to improve the gravity wave detector. There are huge experimental challenges in turning such devices into practical tools. But it offers a path to 40 times the improvement of the gravitational wave detectors needed to observe the birth of black holes.

Astrophysicists have predicted complex gravitational waveforms created by the convulsions of neutron stars as they form black holes. These gravitational waves could allow us to listen to the nuclear physics of a collapsing neutron star.

For example, they have been shown to be able to clearly detect whether neutrons in a star remain as neutrons or decay into a sea of ​​quarks, the tiniest subatomic particles of all. If we could observe how neutrons turn into quarks and then disappear in the singularity of a black hole, the reverse of the Big Bang would be correct where particles formed by creating our universe emerged from the singularity.


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