A Pt-Ti thin-film heating method for de-fluxing SFQ circuits in superconducting computers

This paper proposes a Platinum (Pt)-Ti (Titanium) thin-film heating method for de-fluxing Single Flux Quantum (SFQ) circuits, addressing key limitations of conventional hotspot-based approaches, such as non-uniform temperature distribution, low thermal efficiency, and delayed response. A comprehensive analysis and performance evaluation of different heating methods are conducted to investigate the impact of heat methods on Josephson junction (JJ) de-fluxing. Superconducting computers, which use SFQ logic for high-speed operation and ultra-low power consumption, suffer from logical errors caused by trapped magnetic flux in JJs. To de-flux an SFQ circuit after logic errors, the JJs must be heated above the threshold temperature and then cooled in the absence of a magnetic field. Our studies show that heating the JJs to 22 K or above reliably removes trapped flux. Pt thin-film resistive materials, known for their rapid thermal response and controllable diffusion, offer a more efficient solution for de-fluxing and thermal control in SFQ circuits. The thin-film method demonstrates superior performance, achieving a more uniform temperature distribution (standard deviation of 0.02 K), faster thermal response within 1.2 s, and an optimal heating power of 1500 mW with an effective heating duration of 2 s. These results demonstrate a reliable and efficient de-fluxing method, essential for restoring functionality and ensuring logical error recovery in large-scale superconducting computers.