© R. Jacobson/NIST
NIST physicists John Bollinger (left) and Matt Affolter adjust the laser and optics array used to trap and probe beryllium ions in the large magnetic chamber (white pillar at left). The ion crystal may help detect mysterious dark matter.
NIST physicists John Bollinger (left) and Matt Affolter adjust the laser and optics array used to trap and probe beryllium ions in the large magnetic chamber (white pillar at left). The ion crystal may help detect mysterious dark matter.
The quantum sensor consists of 150 beryllium ions (electrically charged atoms) confined in a magnetic field, so they self-arrange into a flat 2D crystal just 200 millionths of a meter in diameter. Quantum sensors such as this have the potential to detect signals from dark matter — a mysterious substance that might turn out to be, among other theories, subatomic particles that interact with normal matter through a weak electromagnetic field. The presence of dark matter could cause the crystal to wiggle in telltale ways, revealed by collective changes among the crystal's ions in one of their electronic properties, known as spin.
As described in the Aug. 6 issue of Science, researchers can measure the vibrational excitation of the crystal — the flat plane moving up and down like the head of a drum — by monitoring changes in the collective spin. Measuring the spin indicates the extent of the vibrational excitation, referred to as displacement.
This sensor can measure external electric fields that have the same vibration frequency as the crystal with more than 10 times the sensitivity of any previously demonstrated atomic sensor. (Technically, the sensor can measure 240 nanovolts per meter in one second.) In the experiments, researchers apply a weak electric field to excite and test the crystal sensor. A dark matter search would look for such a signal.
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