Toward high-cooperativity spin-magnetomechanics with levitated micromagnets

Abstract

Coupling high-quality mechanical resonators to strong quantum nonlinearities has become an exciting field of research in recent years. These systems offer prospects for long-range entanglement between spins, cooling a mechanical resonator to its ground state, and even production of non-Gaussian states of motion. In this thesis, I will present our progress toward the high-cooperativity regime in a spin-mechanics system. For our mechanical resonator, we levitate micromagnets over a planar type-II superconductor (YBCO). The mechanical modes offer excellent environmental isolation and a high magnetic field gradient-to-mass ratio. We choose to work with nitrogen-vacancy (NV) centers in diamond as our spin due to their long coherence times, large magnetic coupling, and optical initialization and readout. I will present three approaches. First, a characterization of our levitated system and measurement of the coupling to a translational degree of freedom in devices of magnets isolated in silicon pockets. Then, I will describe an approach to shrinking the length scales of the system with patterned NbTiN films on a diamond substrate. Finally, I will discuss coupling to a rotational degree of freedom with an improved platform of NV centers implanted in a diamond membrane (∼ μm thick) placed on a YBCO sample. In addition to these three iterations, I will discuss our investigation into the quality factor limitations of the mechanical resonator. Such improvements pave a clear path to the high-cooperativity regime and will enable near-term milestones such as the detection of a single spin by the levitated system, a gateway for future quantum applications.