Posted on 08/05/2021 12:30:47 PM PDT by Red Badger
Physicists at the National Institute of Standards and Technology (NIST) have linked together, or “entangled,” the mechanical motion and electronic properties of a tiny blue crystal, giving it a quantum edge in measuring electric fields with record sensitivity that may enhance understanding of the universe.
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 August 6, 2021, 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.
Illustration of NIST’s quantum crystal. Credit: Burrows/JILA
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.
“Ion crystals could detect certain types of dark matter — examples are axions and hidden photons — that interact with normal matter through a weak electric field,” NIST senior author John Bollinger said. “The dark matter forms a background signal with an oscillation frequency that depends on the mass of the dark matter particle. Experiments searching for this type of dark matter have been ongoing for more than a decade with superconducting circuits. The motion of trapped ions provides sensitivity over a different range of frequencies.”
Bollinger’s group has been working with the ion crystal for more than a decade. What’s new is the use of a specific type of laser light to entangle the collective motion and spins of a large number of ions, plus what the researchers call a “time reversal” strategy to detect the results.
The experiment benefited from a collaboration with NIST theorist Ana Maria Rey, who works at JILA, a joint institute of NIST and the University of Colorado Boulder. The theory work was critical for understanding the limits of the laboratory setup, offered a new model for understanding the experiment that is valid for large numbers of trapped ions, and demonstrated that the quantum advantage comes from entangling the spin and motion, Bollinger said.
Rey noted that entanglement is beneficial in canceling the ions’ intrinsic quantum noise., However, measuring the entangled quantum state without destroying the information shared between spin and motion is difficult.
“To avoid this issue, John is able to reverse the dynamics and disentangle the spin and the motion after the displacement is applied,” Rey said. “This time reversal decouples the spin and the motion, and now the collective spin itself has the displacement information stored on it, and when we measure the spins we can determine the displacement very precisely. This is neat!”
The researchers used microwaves to produce desired values of the spins. Ions can be spin up (often envisioned as an arrow pointing up), spin down or other angles, including both at the same time, a special quantum state. In this experiment the ions all had the same spin — first spin up and then horizontal — so when excited they rotated together in a pattern characteristic of spinning tops.
Crossed laser beams, with a difference in frequency that was nearly the same as the motion, were used to entangle the collective spin with the motion. The crystal was then vibrationally excited. The same lasers and microwaves were used to undo the entanglement. To determine how much the crystal moved, researchers measured the ions’ spin level of fluorescence (spin up scatters light, spin down is dark).
In the future, increasing the number of ions to 100,000 by making 3D crystals is expected to improve the sensing capability thirtyfold. In addition, the stability of the crystal’s excited motion might be improved, which would enhance the time reversal process and the precision of the results.
“If we are able to improve this aspect, this experiment can become a fundamental resource for detecting dark matter,” Rey said. “We know 85% of the matter in the universe is made of dark matter, but to date we do not know what dark matter is made of. This experiment could allow us in the future to unveil this mystery.”
Co-authors included researchers from the University of Oklahoma. This work is supported in part by the U.S. Department of Energy, Air Force Office of Scientific Research, Defense Advanced Research Projects Agency, Army Research Office and National Science Foundation.
Reference: “Quantum-enhanced sensing of displacements and electric fields with two-dimensional trapped-ion crystals” by K.A. Gilmore, M. Affolter, R.J. Lewis-Swan, D. Barberena, E. Jordan, A.M. Rey and J.J. Bollinger., 5 August 2021, Science. DOI: 10.1126/science.abi5226
Dark Matter Crystal Ping!................
Damn! I was working on the same thing in my garage last Monday.
I wonder where all my antimatter went
200-millionths of a meter = 200-thousandths of a millimeter = 0.2 millimeter.
Why not just say 0.2 millimeter?
200-millionths sounds soo much more techy-talky.........................
Why not just say 0.2 millimeter?
Why not 200 micrometers?
“We know 85% of the matter in the universe is made of dark matter”
yep okdokey I believe you,
Especially how you first detected something, I mean nothing detectable was out there.
In some clusters, the space between galaxies is filled with extremely hot air, scientists cannot see it using visible light telescopes. The gas only can be seen as X-rays or gamma rays. Scientists look at that gas and measure how much there is between galaxies in clusters.
By doing this, they discovered that there must be five times more material in the clusters than we can detect. The invisible matter that we can’t detect is called “dark matter.”
I call it either a measurement error, or a comprehension error
It’s in the dilithium crystals..
‘Dark Matter’ is a place holder for ‘We don’t Know’..................
Last time I tied I jut got this:
Typified by the square root of -!. Perhaps in some universe it does exist.
Just not ours.
https://www.starrett.com/metrology/product-detail/T469HXSP
The Starrett 469, 469M Series Large, Super-Precision Micrometer Head
The micrometer head has a 4-1/16” (103mm) thimble diameter and is graduated to 0.001mm, or 0.002mm for direct reading.
only $1800
Mine was red!
If Dark Matter is invisible, how will they know where it is if they drop it?.......................
I used to use that very item! when I WAS IN metrology!..........
I would not think that 150 atoms of anything could come to 0.2mm no matter how they are arranged. A hairs width is less than 0.2mm.
[[Quantum Crystal With “Time Reversal”]]
Speakin of time reversal, slept backerds last night and woke up the day before- had to relive yesterday ll over again- I’ll be glad when tomorrow gets here!
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