Speaker
Description
The operation of quantum logical devices is necessarily accompanied by irreversibility and therefore dissipation. In practice, this leads to temperature fluctuations in the device and its immediate environment, which can lead to decoherence and fidelity reduction. Measuring the time-resolved temperature fluctuations in a heat absorber then allows estimating the timing and the magnitude of the dissipative events. In a first experiment, we detect in real time the heat dissipated by individual 2π slips of the phase difference in an overdamped Josephson junction, which allows quantifying the major role played by thermal effects in superconducting quantum circuits [1]. We then move to semiconducting silicon and germanium nanostructures (quantum dots and Josephson junctions) and highlight their potential as heat detectors in the vicinity of qubit architectures [2]. Eventually, we discuss an unexpected recently reported temperature dependence of the Larmor frequency fL in electron spin qubits down to the lowest temperatures [3], which leads to reduced coherence times at high drive powers. We show this effect to exist with similar magnitude in hole spin qubits in silicon. We further unveil the temperature susceptibility of fL to be governed by spin-orbit interactions and that qubit operation under well chosen conditions (at so-called thermal sweet spots) allows its complete cancellation.
[1] E. Gümüs et al., Nat. Phys. 19, 196 (2023).
[2] V. Champain et al., Phys. Rev. Appl. 21, 064039 (2024).
[3] B. Undseth et al., Phys. Rev. X 13, 041015 (2023).
