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Â鶹ÒùÔºicists propose a quantum–optomechanical solution to dark-matter detection

An interdisciplinary collaboration between condensed-matter, quantum-optics and particle physicists has the potential to crack the search for low-mass dark matter. The proposed quantum detector builds on EQUS studies of elementary excitations in superfluid helium and advances in opto-mechanics.

Led by EQUS Research Fellow Dr. Chris Baker (UQ), study proposes direct detection of low-mass dark matter via its interactions with superfluid helium confined in an optomechanical cavity.

"" was published in Â鶹ÒùÔºical Review D in August 2024.

The lack of a positive signal in dark-matter direct-detection experiments to date has driven a search for particles with lower and lower masses, requiring development of novel ultra-sensitive detection tools.

"Unfortunately, lower masses imply weaker signals, making traditional particle physics tools inappropriate," says corresponding author EQUS CI Dr. Maxim Goryachev (UWA).

Goryachev and Baker's proposal utilizes superfluid helium, in which dark-matter collisions would cause a mechanical 'ringing' effect (quantified as 'phonons').

A phonon is a collective excitation of particles, and the Quantum and Dark Matter Lab where Goryachev works at UWA has significant experience in applying such quasiparticles' properties to detect and understand other very low energy systems.

It is just one example of the application of sophisticated quantum technologies to precision metrology developed within EQUS's Quantum Engines and Instruments Program.

"The collective vibrations caused by low-mass dark-matter collisions would be extremely small," says Goryachev. "These scattered phonons would be undetectable using current technologies."

"That's where the EQUS-forged links between our lab and the Queensland Quantum Optics Laboratory (QQOL) came in."

Within EQUS, the UQ-based quantum optics lab has led studies in opto-mechanics, using light to control and probe mechanical motion.

At QQOL, Dr. Baker applied his expertise in superfluid opto-mechanics to developing an 'amplification' system based on transducing undetectable low-energy phonons into high-energy (detectable) photons.

The result is the Optomechanical Dark-matter Instrument, or "ODIN."

The device, which can be implemented using well-established technology, would provide access to dark matter in the keV mass range, several orders of magnitude less energetic than existing experiments.

In addition to the contribution to dark-matter science, it is also notable as the first demonstration of applying opto-mechanics to detection of individual particles, i.e. detection of very rare scattering events. This broadens applications of opto-mechanics from being sensors of weak fields.

"We also enjoy the application of quantum instruments to exploration of such an important fundamental field of physics," says Goryachev. "It is energizing to consider wider applications of quantum, beyond more traditional fields such as computing and communications."