Beryllium crystal might help us in the hunt for dark matter. Using a quark of quantum mechanics researchers have created a beryllium crystal which is capable of detecting very weak electromagnetic fields. This could be used to detect hypothetical dark matter particles called axions.
Ana Maria Rey, an atomic physicist at JILA, a joint institute between the National Institute of Standards and Technology and the University of Colorado Boulder said that they created this quantum crystal by using a system of electrodes and magnetic fields to trap 150 charged beryllium particles or ions.
When Rey and her colleagues trapped the ions with their system of fields and electrodes, the atoms self-assembled into a flat sheet twice as thick as human hair. This organized collective resembled a crystal that would vibrate when disturbed by some outside force.
Whenever this beryllium crystal encounters an electromagnetic field it moves in response and by measuring that momentum we could measure the field strength.
But in the world of quantum mechanics, there is a limitation set by the Heisenberg Uncertainty Principle which said that certain properties of a particle such as its position and momentum can’t be known simultaneously with high precision.
But this research group found a way around it with the help of quantum entanglement. Quantum entanglement is a phenomenon where quantum particle’s attributes are inherently linked together.
Here the research team entangled the motion of the beryllium ion with their spins. Quantum systems resemble tiny tops and spin describes the direction, say up or down, that those tops are pointing.
When the crystal vibrated, it would move a certain amount. But because of the uncertainty principle, any measurement of that displacement, or the amount the ions moved, would be subject to precision limits and contain a lot of what’s known as quantum noise, Rey said.
To measure the displacement, “we need a displacement larger than the quantum noise,” she said. Entanglement between the ions’ motions and their spins spreads this noise out, reducing it and allowing the researchers to measure ultra-tiny fluctuations in the crystal. They tested the system by sending a weak electromagnetic wave through it and seeing it vibrate.
This crystal is way more sensitive at detecting a very weak electromagnetic signal than previous quantum sensors. But the team thinks they could create an even more sensitive detector capable of searching axions by using more beryllium ions.
Axions are proposed ultralight dark matter particles with a millionth or a billionth the mass of an electron. Some models of the axion suggest that it may be able to sometimes convert into a photon, in which case it would no longer be dark and would produce a weak electromagnetic field. Were any axions to fly through a lab containing this beryllium crystal, the crystal might pick up their presence.