Interfacing spins and mechanical degrees of freedom allows for a variety of applications and experimental observations. For example, one can deterministically entangle pairs of spins through their coherent coupling with the dynamics of a resonator, even for large spin-spin distance separations and thermal resonator states. Additionally, the resonator could be cooled close to the quantum ground state by bringing a strongly coupled bath of spins into resonance, introducing the possibility of single phonon experiments and quantum state preparation of a mesoscopic object. In our lab, we are pursuing strong, coherent coupling of Nitrogen Vacancy (NV) center spin qubits in diamond, to mechanical resonators via a magnetic field gradient:
- Using the NVs as sensors, we detect the AC motion of a silicon nitride, double-clamped, beam resonator. We are working towards a scheme to enable long-distance, deterministic, NV-NV entanglement via the mechanical mode; we also plan to use an ensemble of NV defects to cool the resonator close to its quantum ground state, using technically feasible parameters (Q ~ one million, spin-phonon coupling ~ 1 kHz, resonator frequency ~ 1 MHz, T ~ 10 K).
- To address this formidable technical challenge of hybrid quantum systems, we are engineering a new platform based on levitated magnets. Currently, we are integrating a levitated micro-magnet with nitrogen-vacancy (NV) centers in diamond as a new platform for quantum applications. The absence of any support structure gives low mechanical damping and a large magnetic moment to mass ratio, thereby enabling strong coupling. This hybrid setup gives controllable access to the rich (tunable) mode spectrum associated with the micro-magnet, consisting of hybridized translational, rotational and internal magnonic modes ranging from kHz to GHz.