Lukas Deeg, Institute for quantum optics and quantum
information, Innsbruck, Austria
Preparing a massive mechanical oscillator near the quantum limit has become a central field in fundamental sciences. Within optomechanics, where the mechanical mode is coupled to a light field, the operation of the mechanical motion near its quantum groundstate is feasible. Contrary to most common setups, our setup consists of a magnetic field sensitive microwave cavity coupled to a magnetic cantilever, a beam mounted with a magnetic tip. The flux sensitivity is given by embedding a SQUID in the center of the cavity. Any motion of the mechanics creates a flux change within the SQUID, which alters the resonance frequency of the cavity. This represents the coupling mechanism of the setup and a measure for the interaction strength is given by the single photon coupling strength, where we achieve a value of around 6 kHz, being one of the highest report values in the field.
Even though the system is operated at cryogenic temperatures, the motional mode of the cantilever is highly populated. To be able to observe quantum behavior of the mechanics it has to be further cooled down, which is usually achieved by sideband cooling using a cavity in the resolved sideband regime. There, the lifetime of the cavity exceeds the mechanical frequency, which overall gets more challenging by using more massive systems as their frequency decreases. Despite being deeply in the unresolved sideband regime, we can show with our setups possibilities to overcome this limitation by using a non-linear cavity originating from the embedded SQUID. The nonlinearity has to be involved in the backaction description and as we show can improve the magnitude of cooling by one order. We could even circumvent the backaction limit being one cooling limit within linear cavity, enabling us to maybe achieve groundstate cooling even though being in the bad cavity limit.
Kollektorn, lecture room, Kemivägen 9, MC2-huset
10 August, 2022, 11:00
10 August, 2022, 12:00