EQUS researchers have devised a universal way of comparing the sensitivity of the many different types of axion detector, without needing specify the signal type.

Understanding the composition of dark matter is one of the greatest challenges facing modern fundamental physics. In the past 5 years, many dark matter searches (for axions in particular) have been proposed and developed. These detectors are sensitive not only to axions, but also gravitational waves, such as those detected by LIGO–VIRGO from collisions between black holes and neutron stars. The only difference is that we’re dealing with 1,000,000 times higher-frequency gravitational waves and thus much smaller objects that produce them. Do these objects exist in the Universe? We won’t know unless we look for them.

The only thing we’re certain about is that the standard model of particle physics is incomplete. Theoretical physicists have proposed a great number of novel particles to look for, such as quark nuggets, domain walls, WIMPzillas and primordial black holes.

These objects will leave traces of gravitational waves very different to axion dark mater, so the sensitivities of proposed detectors cannot be directly translated and compared.

We used a systematic technique to compare the many different axion detectors in terms of their sensitivity to high-frequency gravitational waves, independent of their form.

The many differences in the small details of each experiment, and the need to take into account the different assumptions used in each, make it very difficult to compare experiment sensitivity. Our work enables detectors to be compared irrespective of the details of the diverse types of signal they could detect.

Our result is important for the emerging field of high-frequency gravitational-wave detection and for dark matter searches, both of which could be compared to the “Wild West” of proposals. Our work does not deal with any particular realisation or instrument in detail, but rather sets the rules of the playground for the field where various quantum instruments could be directly compared.

In a way, it could be compared to the early days of gravitational-wave searches, where it took a few decades and the emergence of the field of opto-mechanics to construct a universal technique to compare very different instruments.

It is a universal trend to use quantum technologies, including superconducting particle detectors, levitated nanosystems, superfluids and single-photon sources, in fundamental physics searches. We encourage other EQUS members to look at how their quantum technology could be used in this field. You might be surprised at how much impact it can have!

Read the full paper here: https://doi.org/10.3390/sym14102165.

This story was first published in the 2022 EQUS annual report, and was written by Kristen Harley.