Regensburg 2022 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 37: Superconducting Electronics: SQUIDs, Qubits, Circuit QED
TT 37.12: Talk
Friday, September 9, 2022, 12:30–12:45, H22
A quantum Szilard engine for two-level systems coupled to a qubit — •Martin Spiecker1, Patrick Paluch1, Niv Drucker2, Shlomi Matityahu1, Daria Gusenkova1, Nicolas Gosling1, Simon Günzler1, Dennis Rieger1, Ivan Takmakov1, Francesco Valenti1, Patrick Winkel1, Richard Gebauer1, Oliver Sander1, Gianluigi Catelani3, Alexander Shnirman1, Alexey V. Ustinov1, Wolfgang Wernsdorfer1, Yonatan Cohen2, and Ioan M. Pop1 — 1Karlsruher Institut für Technologie, Karlsruhe, Germany — 2Quantum Machines, Tel Aviv-Yafo, Israel — 3Forschungszentrum Jülich, Jülich, Germany
The innate complexity of solid state physics exposes superconducting quantum circuits to interactions with uncontrolled degrees of freedom degrading their coherence. By using a simple stabilization sequence we show that a superconducting fluxonium qubit is coupled to a two-level system (TLS) environment of unknown origin, with a relatively long energy relaxation time exceeding 50ms. Implementing a quantum Szilard engine with an active feedback control loop allows us to decide whether the qubit heats or cools its TLS environment. The TLSs can be cooled down resulting in a four times lower qubit population, or they can be heated to manifest themselves as a negative temperature environment corresponding to a qubit population of 80%. We show that the TLSs and the qubit are each other's dominant loss mechanism and that the qubit relaxation is independent of the TLS populations. Mitigating TLS environments is therefore not only crucial to improve qubit lifetimes but also to avoid non-Markovian qubit dynamics.