Shot Noise Thermometry

The shot noise thermometer is a method of measuring temperature primarily at cryogenic temperatures using the electrical fluctuations of a quantum tunnel junction. These fluctuations have a component that is a very well understood and simple function of temperature and another component that is totally independent of temperature. By using one to calibrate the other, a simple and powerful thermometer can be constructed.`

The idea of using shot noise in this way was conceived by my graduate advisor Rob Schoelkopf when he was a post doc in Dan Prober's lab at Yale, working on fundamental studies of noise in mesoscopic wires(tiny wires, with a specific technical definition of "tiny"). The work he was doing was of a very pure fundamental nature, the kind that is very difficult to get funded and this is a great example of how such "pure" research can lead to surprisingly useful applied work. What started as a study of fundamental noise processes in tiny wires turned into a ultra low temperature practical thermometer, and from there to a amplifier noise calibration system which might some day be useful at higher temperatures. As part of my thesis work I also made a classroom type demonstration that I was able to successfully demonstrate during the thesis defense at 77 K.

There are several groups around the world pushing this stuff forward on both the thermometry and the amplifier calibration. I'm mostly not involved, but still have some interest in it.

While this has been a very educational and interesting project for many years, I now believe that at this time in human history, working on anything below 77 kelvin in temperature is a huge waste of time and resources. Low temperature physics has mostly been a giant boondoggle, and the problems it claims to solve could be solved in other ways if we re-organized science and technology on better lines. The ideas contained in this work can carry over into useful things, and I will certainly work on it as needed to make a living, but scientifically I consider all work below 77K to be a dangerous waste of scientific resources.