NIST set to shake up temperature with quantum thermometer

Written by Richard Chirgwin,

A moment with Google will reveal all kinds of cranks offering “free” energy from quantum “zero-point” phenomena, but it’s a real thing with real effects.

At the tiniest scales, quanta vibrate, even at their lowest energy. If all motion ceased, an observer would be able to breach uncertainty theory. nano

Now, National Institute for Science an Technology (NIST) boffins reckons zero-point motion could help do for temperature what silicon spheres will do for weight: tie a measurement to a fundamental property of the universe.

So far, NIST says it’s only carried out a demonstration of the technique, and currently it’s only accurate to a few percentage points.

But you have to start somewhere, and here’s where NIST has started: the researchers used a laser to observe a nanoscale beam of silicon nitride.

To see these picometre vibrations, the beam has a reflective cavity; the vibrations cause small changes in colour of the reflected light.

To get a fundamental unit for temperature, NIST says, the “zero point” motion has to be extracted:

“This motion is independent of temperature, and has a well-known amplitude fundamentally dictated by quantum mechanics,” the release notes. “By comparing the relative size of the thermal vibration to the quantum motion, the absolute temperature can be determined.”

“The process of measuring the beam provides a method to distinguish quantum and thermal fluctuations. When photons from the laser bounce off the sides of the beam, they give it slight kicks, inducing correlations that make the quantum motion more pronounced,” the release continues.

NIST reckons it will ultimately be able to fabricate this technique alongside on-chip photonic thermometers it has also developed, to help provide an integrated temperature standard.

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