Why does the dephasing time saturate in open semiconductor quantum dots?
In plain words
Interference measurements on small GaAs electron cavities (open quantum dots) show the phase-coherence time leveling off near 0.1 K. Which source limits it in these clean semiconductor devices remains unclear.
Precise statement
In open GaAs/AlGaAs quantum dots, $\tau_\phi$ extracted from weak-localization and conductance-fluctuation statistics saturates at low T; Huibers et al. (Physical Review Letters 83, 5090, 1999) studied this saturation together with the dephasing caused by applied microwave radiation. Identify the limiting source (residual electron heating, external radiation, charge fluctuators in the heterostructure, nuclear spins) from the dependence of the saturated $\tau_\phi$ on dot size, lead coupling and independently measured electron temperature.
What would settle it
$\tau_\phi$ versus on-chip-measured electron temperature in dots of varied size and filtering, showing which candidate source scales as predicted.