nK
nanokelvin
Temperatureexact by definition
A nanokelvin is 10⁻⁹ K, an exact SI prefix on the base unit. It is the working scale of ultracold atomic physics: a Bose-Einstein condensate forms in the tens to hundreds of nanokelvin, and the coldest bulk matter ever made sits well under one.
| 1 nK | -273.15 °C |
Where the unit came from
Laser cooling and evaporative cooling reach this range by removing energy one photon at a time, then letting the fastest atoms escape. The 1997 and 2001 Nobel Prizes in Physics went to the two halves of that technique.
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