We’re proud to celebrate a significant milestone at 202Q-lab.

Oscar Stommendal successfully defended his Master’s thesis: a proof-of-concept study of extended heat-bath algorithmic cooling on a superconducting two-qubit chip connected by a tunable coupler.

Qubit initialization remains one of quantum computing’s most persistent challenges. Oscar’s work investigates how entropy can be systematically redistributed within a set of qubits to cool a subset of these into their ground states by coupling the qubits to a thermal environment: a framework known as heat-bath algorithmic cooling.

At the heart of the implementation is the β-SWAP: an engineered operation that transfers entropy from the target qubit to a coupler qubit. Each β-SWAP is followed by resonator-assisted coupler re-thermalization, dissipating the extracted entropy to the external environment and enabling optimal cooling over repeated cycles.

Oscar experimentally demonstrated both operations, achieving at least 99% population transfer for the β-SWAP alongside a 3 μs coupler re-thermalization reaching a residual excited state population of 4 %. While the full cooling protocol did not yet produce a definitive cooling effect consistent with theoretical predictions, the path forward is clear: optimize device parameters and apply more advanced calibration techniques. This is an important step toward optimal qubit initialization in superconducting circuits.

On behalf of everyone at 202Q-lab, congratulations, Oscar. We wish him all the very best in the chapters ahead!