Quantum cavity electro-mechanics with ultra-high impedance microwave circuits

Talk

Superconducting circuits are at the focus of quantum engineering research because of their potential for scalable quantum information processing and simulation. One disadvantage of circuit QED systems is that they can only operate in ultra-cold environments where thermal noise and resistive losses are negligible. We are working towards an on-chip integrated microwave-photonic device, which has the potential to efficiently convert microwave to telecom wavelength photons using radiation pressure. The performance of our device is highly dependent on the ability to fabricate a circuit with small mechanically compliant capacitor gaps, low parasitic capacitance, and high mechanical, microwave and optical quality factors. We are currently utilizing compact LC circuits suspended on silicon nitride membranes to efficiently couple to the mechanical modes of one dimensional acoustic bandgap nanobeam resonators compatible with nano-photonics. With this new platform we demonstrate ground state cooling of the dielectric beam's fundamental mode as well as mechanically mediated efficient microwave frequency conversion over 2 GHz. In the future, the integration with Josephson qubits should allow to synthesize and manipulate acoustic quantum states without the need for active cooling. Coupling these excitations to mechanical wave guides, entanglement between itinerant multi-phonon states could be studied in analogy to quantum optical systems. Coupling to photonic crystals on the other hand would put within reach the realization of hybrid long distance quantum communication networks.

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