Cryoselle: Dilution Fridge Qubit
Thermodynamics & Statistical Physics arc, page 70 of 193. Back to The Pixelated Physics Universe
Who they are
Cryoselle has one line, and says it often: “Hf ≫ kt. finally, silence.”
Cryoselle is a character of the Thermodynamics & Statistical Physics arc: drawn in pixels, ruled by one piece of real physics, and never allowed to break it.
The physics
Mean thermal photon number n̄ = 1/(ehf/kT − 1). For a 5 GHz qubit mode at 20 mK, hf/kT ≈ 12, so n̄ ≈ 6 × 10⁻⁶: the mode is almost always empty.
$$ \begin{gathered} \bar n = \frac{1}{e^{hf/kT} - 1} \\ f = 5\ \text{GHz},\ T = 20\ \text{mK}:\quad \frac{hf}{kT} \approx 12,\quad \bar n \approx 6 \times 10^{-6} \end{gathered} $$
| Symbol | Meaning | SI unit |
|---|---|---|
| $\bar n$ | mean thermal photon number | — |
| $h$ | Planck constant | J·s |
| $f$ | mode frequency | Hz |
| $k$ | Boltzmann constant | J/K |
| $T$ | temperature | K |
Sources
Crossovers
Cryoselle meets Asymptor (Third Law of Thermodynamics). Cryoselle runs her dilution fridge at 20 mK and calls it quiet, since hf/k_BT is about 12 for her qubit. Asymptor reminds her that colder is always possible and zero never is.
Cryoselle meets Superfluid (Quantum Fluid at Near Absolute Zero). Cryoselle's dilution fridge runs on helium: a mixture of helium-3 and helium-4, where superfluid helium-4 is an inert background for helium-3 to "evaporate" into. That is how she reaches 20 mK.
Cryoselle meets Boundraith (Kapitza Resistance). Cryoselle must cool her sample through boundaries, and Boundraith guards every one. Kapitza resistance grows as the temperature falls, so cryogenic designers use sintered silver to multiply the contact area.
Wear the lore
- Cryoselle, Abbess of the Twenty Millikelvin Mug
- Related infographic poster: Mercury at 4.2 K – Plate 061 Physics Poster
Concept keywords: Dilution Fridge Qubit, Cryoselle, Thermodynamics & Statistical Physics, physics lore, Pixelated Physics