On increasing the temperature, one finds experimentally that the plateaux acquire a finite slope until they are no longer resolved. This is a consequence of the thermal smearing of the Fermi-Dirac distribution. The conductance steps should disappear for T ≲ ≲ Δ Δ E / 4 k B ≈ ≈ 4 K (here ∆ E is the subband splitting at the Fermi level). This is confirmed both by experiment and by numerical calculations.