Grant: Alliance Grants

Advancing our strength in quantum computing relies on exploring more than simply quantum processors. It must also include developing the subsystems to enable complete quantum computing hardware, such as quantum memories and wavelength convertors. Hybrid quantum systems are powerful for such applications, allowing new functionalities due to the composite components. Amongst these, hybrid systems that incorporate magnonics are extremely promising, in part because they have already been used in classical electronics, but also because they can be readily incorporated into - and strongly coupled to - microwave cavities. Unfortunately, the material dissipation in even the best magnonic materials is insufficient for quantum applications. Therefore, we propose to "artificially" improve the magnon dissipation rate through feedback control techniques. In this proposal, we will develop a solid theoretical framework for both measurement-based and coherent (quantum) feedback specific to cavity magnonic and magnomechanical systems. Feedback techniques, bespoke to the needs of this system, will then be implemented in the laboratory with the aim of cooling massive magnomechanical systems into the quantum ground state. This will open the door for quantum memory applications in particular, where quantum information from a microwave circuit is stored for long timescales due to the feedback enhanced magnon dissipation.