Abstract
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.
| Original language | English |
|---|---|
| Article number | L042010 |
| Journal | Physical review research |
| Volume | 7 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - Oct 2025 |
| MoE publication type | A1 Journal article-refereed |
Funding
This work was funded by the Research Council of Finland Centre of Excellence program (Projects No. 352925 and No. 336810) and Grants No. 316619 and No. 349594 (THEPOW). We also acknowledge funding from the European Research Council under Advanced Grant No. 101053801 (ConceptQ) and the provision of facilities and technical support by Aalto University at OtaNano-Micronova Nanofabrication Centre. We thank Jukka Pekola, Bayan Karimi, Jian Ma, Satrya Christoforus, Visa Vesterinen, Tapio Ala-Nissila, and Matti Silveri for discussions. We also thank Jukka-Pekka Kaikkonen and Kimmo Sten at VTT Technical Research Center for fabricating the Nb structures.