Anyone who’s been at UW–Madison in January will argue that the coldest place on campus is a stop on the Number 80 bus line, waiting while the relentless wind beats sleet against your face. (A bus every five minutes, my foot.) But the coldest place on campus, and among the coldest places in the known universe, is in Chamberlin Hall, in the lab of physics professor Shimon Kolkowitz. Kolkowitz maintains a vacuum chamber in which he uses lasers to supercool strontium atoms and create a 0.5 cubic millimeter space where the temperature drops to 500 nanokelvin. If you’re thinking, “Wow, 500 sounds like a lot of nanokelvins,” you’re wrong. Remember that nano means billionth: 500 nanokelvins is 0.0000005 degrees above absolute zero, or –273.1499995 degrees Celsius, or –459.6699991 degrees Fahrenheit. But creating such a tiny cold spot isn’t just literally and figuratively cool: it’s also necessary for certain kinds of studies. Kolkowitz makes atomic clocks that are accurate to 19 digits of precision. “There is a community of atomic physicists who create ultracold atoms like these for a variety of research,” he says, “including forming exotic phases of matter, as well as to make very precise clocks as we do in my group, or to try to use these atoms as the ‘quantum bits’ in a quantum computer.” Another member of that community is also on campus: Mark Saffman, whose lab is down the hall from Kolkowitz’s. “My lab is really in a tie with Mark’s for coldest place,” Kolkowitz admits.
Coldest Place on Campus
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