We experimentally demonstrate the fast generation of thermal states of a transmon using a single-junction quantum-circuit refrigerator (QCR) as an in-situ-tunable environment. Through single-shot readout, we monitor the transmon up to its third-excited state, assessing population distributions controlled by QCR drive pulses. Whereas cooling can be achieved in the weak-drive regime, high-amplitude pulses can generate Boltzmann-distributed populations from a temperature of 110 mK up to 500 mK within 100 ns. As we propose in our work, this fast and efficient temperature control provides an appealing opportunity to demonstrate a quantum heat engine. Our results also pave the way for efficient dissipative state preparation and for reducing the circuit depth in thermally assisted quantum algorithms and quantum annealing.
@article{arxiv.2402.09594,
title = {Rapid on-demand generation of thermal states in superconducting quantum circuits},
author = {Timm Fabian Mörstedt and Wallace Santos Teixeira and Arto Viitanen and Heidi Kivijärvi and Maaria Tiiri and Miika Rasola and Andras Marton Gunyho and Suman Kundu and Louis Lattier and Vasilii Vadimov and Gianluigi Catelani and Vasilii Sevriuk and Johannes Heinsoo and Jukka Räbinä and Joachim Ankerhold and Mikko Möttönen},
journal= {arXiv preprint arXiv:2402.09594},
year = {2025}
}