Primary thermometry triad at 6 mK in mesoscopic circuits

Abstract

Quantum physics emerge and develop as temperature is reduced. Although mesoscopic electrical circuits constitute an outstanding platform to explore quantum behaviour, the challenge in cooling the electrons impedes their potential. The strong coupling of such micrometre-scale devices with the measurement lines, combined with the weak coupling to the substrate, makes them extremely difficult to thermalize below 10 mK and imposes in situ thermometers. Here we demonstrate electronic quantum transport at 6 mK in micrometre-scale mesoscopic circuits. The thermometry methods are established by the comparison of three in situ primary thermometers, each involving a different underlying physics. The employed combination of quantum shot noise, quantum back action of a resistive circuit and conductance oscillations of a single-electron transistor covers a remarkably broad spectrum of mesoscopic phenomena. The experiment, performed in vacuum using a standard cryogen-free dilution refrigerator, paves the way towards the sub-millikelvin range with additional thermalization and refrigeration techniques.

500 microkelvin nanoelectronics

“…In a typical dilution refrigerator, T p > 5 mK, and specially built systems reach 1.8 mK [12], which limits T e > T p to the millikelvin regime. The lowest static electron temperature reached with this technique was T e = 3.9 mK [13] in an all-metallic nanostructure, and other experiments reached similar values [14][15][16] in semiconductor heterostructures.This technological limitation can be bypassed by adia- * These authors contributed equally to this work.batic magnetic refrigeration, which relies on the constant occupation probability of the energy levels of a spin system, ∼ exp(−gµBm/k B T ) in the absence of heat exchange with the environment [17]. Here, k B T is the thermal energy at a temperature of T , gµB is the energy split between adjacent levels at a magnetic field of B and m is the spin index.…”

Transmitting the quantum state of electrons across a metallic island with Coulomb interaction

“…1, with the bottom MZI beam splitter and the uncolorized left gate set, respectively, to fully transmit and reflect the outer edge channel). See [22] for further details on * These authors contributed equally to this work. † e-mail: frederic.pierre@c2n.upsaclay.fr this experimental setup.…”

On-and-off chip cooling of a Coulomb blockade thermometer down to 2.8 mK

“…Each wire is cooled by its own, separate nuclear refrigerator in form of a large Cu plate. However, despite recent progress [18][19][20][21][22][23][24][25] , it remains very challenging to cool nanostructures even below 10 mK. Due to reduced thermal coupling, these samples are extremely susceptible to heat leaks such as vibrations 25 , microwave radiation 26,27 , heat release 17 and electronic noise 20 .…”