Thiago P. Mayer Alegre

In this Letter we use resolved sideband laser cooling to cool a mesoscopic mechanical resonator to near its quantum ground state (phonon occupancy 2.6±0.2), and observe the motional sidebands generated on a second probe laser. Asymmetry in the sideband amplitudes provides a direct measure of the displacement noise power associated with quantum zero-point fluctuations of the nanomechanical resonator, and allows for an intrinsic calibration of the phonon occupation number.

The nitrogen vacancy (NV) center in diamond is promising as an electron spin qubit due to its long-lived coherence and optical addressability. The ground state is a spin triplet with two levels $({m}_{s}=\ifmmode\pm\else\textpm\fi{}1)$ degenerate at zero magnetic field. Polarization-selective microwave excitation is an attractive method to address the spin transitions independently since this allows operation down to zero magnetic field. Using a resonator designed to produce circularly polarized microwaves, we have investigated the polarization selection rules of the NV center. We first apply this technique to NV ensembles in [100]- and [111]-oriented samples. Next, we demonstrate an imaging technique, based on optical polarization dependence, which allows rapid identification of the orientations of many single NV centers. Finally, we test the microwave polarization selection rules of individual NV centers of known orientation.

We demonstrate an ultrahigh-Q slotted two-dimensional photonic crystal cavity capable of obtaining strong interaction between the internal light field and the mechanical motion of the slotted structure. The measured optical quality factor is Q=1.2×106 for a cavity with an effective modal volume of Veff=0.04(λ)3. Optical transduction of the thermal motion of the fundamental in-plane mechanical resonance of the structure (νm=151 MHz) is performed, from which a zero-point motion optomechanical coupling rate of g∗/2π=320 kHz is inferred. Dynamical back-action of the optical field on the mechanical motion, resulting in cooling and amplication of the mechanical motion, is also demonstrated.