Probing fast quantum circuit refrigeration in the quantum regime
Shuji Nakamura, Teruaki Yoshioka, Sergei Lemziakov, Dmitrii Lvov, Hiroto Mukai, Akiyoshi Tomonaga, Shintaro Takada, Yuma Okazaki, Nobu‐Hisa Kaneko, Jukka P Pekola, Jaw-Shen Tsai · Physical Review Applied · 2025
Photon-absorption-based quantum circuit refrigeration is crucial to developing superconducting quantum computers, particularly for initializing qubits. However, precise and rapid measurement of residual photons in the circuit immediately after absorption has been a significant technical challenge. This study employs the ac Stark shift of superconducting qubits to detect sub-photon-level energies in the circuit, confirming the effectiveness of the fast refrigeration even in the quantum regime. These results will facilitate the development of more efficient quantum refrigeration devices and faster, high-fidelity qubit initialization.