The advent of laser cooling techniques revolutionized the study of many atomic-scale systems. This has fueled progress towards quantum computers by preparing trapped ions in their motional ground state [1], and generating new states of matter by achieving BoseEinstein condensation of atomic vapors [2]. Analogous cooling techniques [3, 4] provide a general and flexible method for preparing macroscopic objects in their motional ground state, bringing the powerful technology of micromechanics into the quantum regime. Cavity optoor electro-mechanical systems achieve sideband cooling through the strong interaction between light and motion [5][6][7][8][9][10][11][12][13][14][15]. However, entering the quantum regime, less than a single quantum of motion, has been elusive because sideband cooling has not sufficiently overwhelmed the coupling of mechanical systems to their hot environments. Here, we demonstrate sideband cooling of the motion of a micromechanical oscillator to the quantum ground state. Entering the quantum regime requires a large electromechanical interaction, which is achieved by embedding a micromechanical membrane into a superconducting microwave resonant circuit. In order to verify the cooling of the membrane motion into the quantum regime, we perform a near quantumlimited measurement of the microwave field, resolving this motion a factor of 5.1 from the Heisenberg limit [3]. Furthermore, our device exhibits strong-coupling allowing coherent exchange of microwave photons and mechanical phonons [16]. Simultaneously achieving strong coupling, ground state preparation and efficient measurement sets the stage for rapid advances in the control and detection of non-classical states of motion [17,18], possibly even testing quantum theory itself in the unexplored region of larger size and mass [19]. The universal ability to connect disparate physical systems through mechanical motion naturally leads towards future methods for engineering the coherent transfer of quantum information with widely different forms of quanta.Mechanical oscillators that are both decoupled from their environment (high quality factor Q) and placed in the quantum regime could allow us to explore quantum mechanics in entirely new ways [17][18][19][20][21]. For an oscillator to be in the quantum regime, it must be possible to prepare it in its ground state, to arbitrarily manipulate its quantum state, and to detect its state near the Heisenberg limit. In order to prepare an oscillator in its ground state, its temperature T must be reduced such that k B T < Ω m , where Ω m is the resonance frequency of the oscillator, k B is Boltzmann's constant, and is the reduced Planck's constant. While higher resonance frequency modes (> 1 GHz) can meet this cooling requirement with conventional refrigeration (T < 50 mK), these stiff oscillators are difficult to control and to detect within their short mechanical lifetimes. One unique approach using passive cooling has successfully overcome these difficulties by using a piezoelectric dilatation osci...

Demonstrating and exploiting the quantum nature of macroscopic mechanical objects would help us to investigate directly the limitations of quantum-based measurements and quantum information protocols, as well as to test long-standing questions about macroscopic quantum coherence. Central to this effort is the necessity of long-lived mechanical states. Previous efforts have witnessed quantum behaviour, but for a low-quality-factor mechanical system. The field of cavity optomechanics and electromechanics, in which a high-quality-factor mechanical oscillator is parametrically coupled to an electromagnetic cavity resonance, provides a practical architecture for cooling, manipulation and detection of motion at the quantum level. One requirement is strong coupling, in which the interaction between the two systems is faster than the dissipation of energy from either system. Here, by incorporating a free-standing, flexible aluminium membrane into a lumped-element superconducting resonant cavity, we have increased the single-photon coupling strength between these two systems by more than two orders of magnitude, compared to previously obtained coupling strengths. A parametric drive tone at the difference frequency between the mechanical oscillator and the cavity resonance dramatically increases the overall coupling strength, allowing us to completely enter the quantum-enabled, strong-coupling regime. This is evidenced by a maximum normal-mode splitting of nearly six bare cavity linewidths. Spectroscopic measurements of these 'dressed states' are in excellent quantitative agreement with recent theoretical predictions. The basic circuit architecture presented here provides a feasible path to ground-state cooling and subsequent coherent control and measurement of long-lived quantum states of mechanical motion.

We present new arcminute-resolution maps of the Cosmic Microwave Background temperature and polarization anisotropy from the Atacama Cosmology Telescope, using data taken from 2013–2016 at 98 and 150 GHz. The maps cover more than 17,000 deg2, the deepest 600 deg2 with noise levels below 10μK-arcmin. We use the power spectrum derived from almost 6,000 deg2 of these maps to constrain cosmology. The ACT data enable a measurement of the angular scale of features in both the divergence-like polarization and the temperature anisotropy, tracing both the velocity and density at last-scattering. From these one can derive the distance to the last-scattering surface and thus infer the local expansion rate, H 0. By combining ACT data with large-scale information from WMAP we measure H 0=67.6± 1.1 km/s/Mpc, at 68% confidence, in excellent agreement with the independently-measured Planck satellite estimate (from ACT alone we find H 0=67.9± 1.5 km/s/Mpc). The ΛCDM model provides a good fit to the ACT data, and we find no evidence for deviations: both the spatial curvature, and the departure from the standard lensing signal in the spectrum, are zero to within 1σ; the number of relativistic species, the primordial Helium fraction, and the running of the spectral index are consistent with ΛCDM predictions to within 1.5–2.2σ. We compare ACT, WMAP, and Planck at the parameter level and find good consistency; we investigate how the constraints on the correlated spectral index and baryon density parameters readjust when adding CMB large-scale information that ACT does not measure. The DR4 products presented here will be publicly released on the NASA Legacy Archive for Microwave Background Data Analysis.