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We study the mechanical properties of stoichiometric SiN resonators through a combination of spectroscopic and interferometric imaging techniques. At room temperature, we demonstrate ultrahigh quality factors of 5×107 and a f×Q product of 1×1014  Hz. To our knowledge, these correspond to the largest values yet reported for mesoscopic flexural resonators. Through a comprehensive study of the limiting dissipation mechanisms as a function of resonator and substrate geometry, we identify radiation loss through the supporting substrate as the dominant loss process. In addition to pointing the way towards higher quality factors through optimized substrate designs, our work realizes an enabling platform for the observation and control of quantum behavior in a macroscopic mechanical system.

We realize a nondegenerate parametric amplifier in an ultrahigh Q mechanical membrane resonator and demonstrate two-mode thermomechanical noise squeezing. Our measurements are accurately described by a two-mode model that attributes this nonlinear mechanical interaction to a substrate-mediated process which is dramatically enhanced by the quality factors of the individual modes. This realization of strong multimode nonlinearities in a mechanical platform compatible with quantum-limited optical detection and cooling makes this a powerful system for nonlinear approaches to quantum metrology, transduction between optical and phononic fields and the quantum manipulation of phononic degrees of freedom.

We demonstrate the nondestructive imaging of a lattice gas of ultracold bosons. Atomic fluorescence is induced in the simultaneous presence of degenerate Raman sideband cooling. The combined influence of these processes controllably cycles an atom between a dark state and a fluorescing state while eliminating heating and loss. Through spatially resolved sideband spectroscopy following the imaging sequence, we demonstrate the efficacy of this imaging technique in various regimes of lattice depth and fluorescence acquisition rate. Our work provides an important extension of quantum gas imaging to the nondestructive detection, control and manipulation of atoms in optical lattices. In addition, our technique can also be extended to atomic species that are less amenable to molasses-based lattice imaging.PACS numbers: 37.10. Jk,67.85.Hj,03.75.Lm, The creation, control and manipulation of ultracold atomic gases in tailored optical potentials has spurred enormous interest in harnessing these mesoscopic quantum systems to the realization of ultracold analogues of correlated electronic materials [1,2], studies of nonequilibrium dynamics in isolated quantum many-body systems [3] and quantum metrology [4]. The dilute nature of these gases and the weak interactions impose stringent restrictions on the energy, entropy and means of manipulating and probing these systems. This has led to the development of novel techniques to cool and image these gases at ever increasing levels of precision and resolution. In this context, the in situ imaging of lattice gases at high spatial resolution has emerged as a powerful tool for the study of Hubbard models [5][6][7][8] and quantum information processing [9].Here, we demonstrate a nondestructive imaging technique for ultracold lattice gases. The scheme relies on extracting fluorescence from the atoms while simultaneously cooling them to the lowest band of the lattice via Raman sideband cooling (RSC) [10][11][12]. Through a combination of sideband spectroscopy and time-of-flight measurements, we demonstrate broad regimes of fluorescence acquisition rates and lattice depths for which the imaging scheme preserves the spatial location, the spin state and the vibrational occupancy of the lattice gas.The principle of the imaging sequence is depicted in Fig. 1. Raman sideband cooling is employed to cool individual atoms within an optical lattice to the lowest vibrational band while simultaneously pumping the atoms to the high field seeking state. In the case of 87 Rb atoms used in our study, this state is denoted by |g = |F = 1, m F = 1; ν = 0 where ν is the vibrational state of the atom within a lattice site. Importantly, this state is a dark state with respect to the optical fields used for Raman cooling. As such, the atoms do not emit any fluorescence while in this ground state. Fluorescence is induced in these atoms by shining a circularly polarized (σ − ) beam resonant with the F = 1 → F = 0 (D2) transition. Simultaneous use of RSC mitigates the increase in temperature caused by this fluor...

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