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.

When two physical systems share the quantum property of entanglement, measurements of one system appear to determine the state of the other. This peculiar property is used in optical, atomic, and electrical systems in an effort to exceed classical bounds when processing information. We extended the domain of this quantum resource by entangling the motion of a macroscopic mechanical oscillator with a propagating electrical signal and by storing one half of the entangled state in the mechanical oscillator. This result demonstrates an essential requirement for using compact and low-loss micromechanical oscillators in a quantum processor, can be extended to sense forces beyond the standard quantum limit, and may enable tests of quantum theory.

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 Bose-Einstein 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 tempera-ture 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 osc...

In recent years microfabricated microwave cavities have been extremely successful in a wide variety of detector applications. In this article we focus this technology on the challenge of quantum-limited displacement detection of a macroscopic object. We measure the displacement of a nanomechanical beam by capacitively coupling its position to the resonant frequency of a superconducting transmission-line microwave cavity. With our device we realize near state-of-the-art mechanical force sensitivity (3 aN/ √ Hz) and thus add to only a handful of techniques able to measure thermomechanical motion at 10's of milliKelvin temperatures. Our measurement imprecision reaches a promising 30 times the expected imprecision at the standard quantum limit, and we quantify our ability to extract measurement backaction from our results as well as elucidate the important steps that will be required to progress towards the full quantum limit with this new detector.The advent of micro and nanomechanical resonators has brought the long-standing goal of exploring quantum effects such as superposition and entanglement of macroscopic objects closer to reality. With this ability one could experimentally study decoherence of superposition states thus elucidating questions about the interface between the quantum and classical worlds. Micro and nanomechanical resonators have hastened progress towards macroscopic quantum limits by providing high-frequency, small-dissipation, yet lowmass resonators. Still it remains a challenge to freeze out the thermomechanical motion of these objects to leave only zeropoint fluctuations δx zp and, equally importantly, to detect motion at this level. The problem of detection at the quantum limit is in itself intriguing. As the imprecision of any detector is decreased, measurement backaction emerges to enforce the Heisenberg constraint, which for continuous displacement detection is S im x S ba F ≥ 2 . Here S im x and S ba F are respectively the displacement imprecision and backaction force spectral densities. In fact, at the minimum allowed total position uncertainty, referred to as the standard quantum limit (SQL), the measurement imprecision and backaction must together contribute an uncertainty equal to the zero-point fluctuations.A widely used displacement detector that, in principle, is capable of reaching the SQL is an optical cavity interferometer with a moving mirror [1]. Physically, at the SQL ones knowledge of the mirror position is limited equally by shot noise in the output signal and by motion of the mirror due to quantum fluctuations in the intracavity radiation pressure. This limit has long been of interest in quantum optics and in the gravitational wave detection community. Optical cavities generally outperform all other displacement detectors with regard to measurement imprecision; they can achieve shot-noise limited position sensitivity as low as ∼ 10. Still reaching the SQL has historically been a challenge due to the inaccessibility of quantum backaction effects [3,4]. Recent experimental...