Thermometer uses quantum mechanics to get specific temps.

Applied physics professor Robert Schoelkopf and graduate student Lafe Spietz GRD ’06 have developed a new thermometer — but it is far more accurate than the glass tubes typically found in medicine cabinets.

The thermometer was created using quantum mechanics, and it measure temperatures one-hundredth of a degree above absolute zero.

Schoelkopf and Spietz have been working on the thermometer for the past three years.

“It has turned out much, much better than we hoped, and has gotten very exciting,” Schoelkopf said.

Schoelkopf said he never had a reliable way to measure the temperatures of the materials he worked with in his lab, and so he was constantly performing a crude version of sound measurement. That is when Spietz realized that a thermometer could be developed based on this idea.

“It started as a means to an end, but may have applications for actually defining standards of measurement,” Spietz said.

The new thermometer consists of two pieces of metal, measuring 1 micron by 10 microns. Electrons quantum-mechanically tunnel through the space between the pieces, creating an electrical noise that is then measured. As the temperature rises, there is more electron movement, causing louder noise.

Any object that has electrical conductivity makes noise and that noise is proportionate to its temperature, Spietz said. That sound, however, must be significantly amplified in order to be measured, and in order to find the temperature, the amplifiers must be carefully calibrated.

Schoelkopf and Spietz’s thermometer simplifies the calibration process by measuring shot noise, a sound independent of temperature.

While there are other scientific thermometers on the market, Spietz said none are able to measure low temperatures in the same reliable and certifiable fashion as the one developed by Schoelkopf and Spietz.

“It’s a very clever idea to solve a problem that has been outstanding for 50 years,” Applied Physics Department Chairman Daniel Prober said.

Spietz said other thermometers may be better in certain categories, but none is as good in all areas as their thermometer.

“There’s no other thermometer that does all the things this one does,” said Spietz. “It has a wider range and is more reliable and is easier to use.”

Prober cited two areas with possibilities for practical applications of the thermometer. He said that there are a few hundred labs around the country that would adopt the thermometer as a primary means of measurement if Spietz and Schoelkopf attempt to sell it. In addition, a possible larger market would be in industry, where measuring regular temperatures with absolute standards would be beneficial, Prober said.

“Since the system is electrical, it could be more easily mass produced,” Prober said. “But it is not something that will become a consumer product.”

Spietz has his own goals for the thermometer.

“Where I personally hope to end up is to convince the thermometry community to adopt this,” Spietz said.

Schoelkopf said he is unsure where the project will end, but he said there are many different definitions for ultimate success.

“Turning it into a commercial product would be a successful outcome,” he said. “Understanding the physics of the noise process would also be a successful outcome. We try to ask the questions and just see what the answers are.”

Schoelkopf and Spietz are now working to make the thermometer’s temperature readings more accurate in readings around room temperature.

Applied physics professor Robert Schoelkopf displays the new thermometer he invented with graduate student Lafe Spietz GRD ’06. The device is much more accurate than earlier models, according to its creators.
Allison Stern
Applied physics professor Robert Schoelkopf displays the new thermometer he invented with graduate student Lafe Spietz GRD ’06. The device is much more accurate than earlier models, according to its creators.

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