Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session Y34: Nano/Optomechanics for Quantum Information Processing |
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Sponsoring Units: GQI Room: 704 |
Friday, March 7, 2014 8:00AM - 8:12AM |
Y34.00001: Quantum back-action evading measurement of micro-mechanical motion Junho Suh, Aaron Weinstein, Chan U Lei, Emma Wollman, Keith Schwab Quantum mechanics imposes unavoidable finite back-action in measuring a mechanical resonator's position and places limits on its ultimate sensitivity, which is well known as the standard quantum limit (SQL). However, if the detector couples to only a single quadrature of motion, it is possible to place this quantum back-action in the uncoupled quadrature, realizing sensitivity below SQL. We demonstrate this back-action evading measurement using a micro-electromechanical device tightly coupled to a superconducting microwave resonator. We observe classical and quantum back-action from microwave photons, and demonstrate that the measurement back-action is 9dB lower than that from microwave shot noise. The measurement imprecision reaches 2dB smaller than the zero-point fluctuation level at the same time, showing the detector noise product five times from the quantum limit. We expect further improvements of this technique would provide a route to the generation of quantum squeezed states of motion, highly desirable for precision measurement of force and quantum engineering applications. [Preview Abstract] |
Friday, March 7, 2014 8:12AM - 8:24AM |
Y34.00002: Manipulating a qubit through the backaction of sequential partial measurements and real-time feedback Cristian Bonato, Machiel Blok, Matthew Markham, Daniel Twitchen, Viatcheslav Dobrovitski, Ronald Hanson Quantum measurements not only extract information from a system but also alter its state. Although the outcome of the measurement is probabilistic, the backaction imparted on the measured system is accurately described by quantum theory. Therefore, quantum measurements can be exploited for manipulating quantum systems without the need for control fields. We demonstrate measurement-only state manipulation on a nuclear spin qubit in diamond by adaptive partial measurements. We implement the partial measurement via tunable correlation with an electron ancilla qubit and subsequent ancilla readout. We vary the measurement strength to observe controlled wavefunction collapse and find post-selected quantum weak values beyond 10. By combining a novel quantum non-demolition readout on the ancilla with real-time adaptation of the measurement strength, we realize steering of the nuclear spin to a target state by measurements alone. Besides being of fundamental interest, adaptive measurements can improve metrology applications and are key to measurement-based quantum computing. [Preview Abstract] |
Friday, March 7, 2014 8:24AM - 8:36AM |
Y34.00003: Narrow spectral peaks induced by phase noise in modulated oscillators Mark Dykman, Yaxing Zhang, J. Moser, A. Eichler, A. Bachtold We show that frequency noise leads to additional peaks in the power spectra of modulated vibrational systems. We also provide experimental evidence of the occurrence of such peaks in suspended carbon nanotubes. The peaks are shown to emerge even for linear vibrations, in which case their parameters are independent of the thermal noise that accompanies relaxation. They can be thought of as a result of weakly inelastic scattering of the modulating field due to frequency noise. The peaks are centered near the modulation frequency and near the oscillator eigenfrequency, with strengths that depend on the noise spectrum. The peak near the modulation frequency is determined by the low-frequency part of the noise spectrum and can be much narrower than the peak in the oscillator absorption spectrum. We also show that the vibration nonlinearity can lead to a characteristic extra structure in the power spectrum in the presence of modulation. The modulation-induced spectral peaks are not only a direct indicator of frequency fluctuations, but they also provide information about the fluctuation intensity and spectrum thus enabling full characterization of the fluctuations. [Preview Abstract] |
Friday, March 7, 2014 8:36AM - 8:48AM |
Y34.00004: The role of broken potential symmetry for nanomechanical resonators Alexander Eichler, Joel Moser, Mark Dykman, Adrian Bachtold Vibrational modes in nanomechanical systems as well as in nonlinear microwave cavities can have broken inversion symmetry, which can significantly affect the mode dynamics. We demonstrate a technique that allows us to reveal the symmetry breaking and to study its manifestation in linear and nonlinear resonant response. We study vibrational modes of carbon nanotubes, where the symmetry breaking is associated with the nanotube bending. We find that symmetry breaking leads to spectral broadening of mechanical resonances, and to an apparent quality factor that drops below 100 at room temperature. The low quality factor at room temperature is a striking feature of nanotube resonators whose origin has remained elusive for many years. Our results shed light on the pivotal role played by symmetry breaking in the dynamics of carbon nanotube mechanical resonators (to be published in Nature Communications). [Preview Abstract] |
Friday, March 7, 2014 8:48AM - 9:00AM |
Y34.00005: Two-mode squeezed states in cavity optomechanics via single-mode reservoir engineering Matthew Woolley, Aashish Clerk The generation and verification of a macroscopic, all-mechanical entangled state is a major goal and (at present) outstanding task in the study of mechanical systems in the quantum regime. The canonical continuous-variable entangled state is the two-mode squeezed state. Here we describe how to prepare and detect a highly-pure, all-mechanical two-mode squeezed state in an optomechanical system via coupling to only one (rather than two [1,2]) cavity mode(s). The approach taken may be viewed as a perturbation of a two-mode back-action-evading measurement [3], and generalizes an earlier proposal for single-mode mechanical squeezing [4].\\[4pt] [1] Y.-D. Wang and A. A. Clerk, Phys. Rev. Lett. 110, 253601 (2012).\\[0pt] [2] H. Tan, G. Li, and P. Meystre, Phys. Rev. A 87, 033829 (2013).\\[0pt] [3] M. J. Woolley and A. A. Clerk, Phys. Rev. A 87, 063846 (2013).\\[0pt] [4] A. Kronwald, F. Marquardt, and A. A. Clerk, arXiv:1307.5309. [Preview Abstract] |
Friday, March 7, 2014 9:00AM - 9:12AM |
Y34.00006: Room-temperature ultra-sensitive mass spectrometer via dynamic decoupling Nan Zhao, Zhang-qi Yin We propose an ultra-sensitive mass spectrometer based on a coupled quantum-bit-oscillator system. Under dynamical decoupling control of the quantum bit (qubit), the qubit coherence exhibits a comb structure in time domain. The time-comb structure enables high precision measurement of oscillator frequency, which can be used as an ultra-sensitive mass spectrometer. Surprisingly, in ideal case, the sensitivity of the proposed mass spectrometer, which scales with the temperature $T$ as $T^{-1/2}$, has better performance in higher temperature. While taking into account qubit and oscillator decay, we show that the optimal sensitivity is independent on environmental temperature $T$. With present technology on solid state spin qubit and high-quality optomechanical system, our proposal is feasible to realize an ultra-sensitive mass spectrometer in room temperature. [Preview Abstract] |
Friday, March 7, 2014 9:12AM - 9:24AM |
Y34.00007: High-Q Bulk Acoustic Quartz Resonators and Application to Hybrid Quantum Systems Michael Tobar, Maxim Goryachev, Daniel Creedon, Serge Galliou Latest results on cryogenically cooled Balk Acoustic Wave quartz resonators will be presented. We demonstrate the ability of such devices to have quality factors approaching $10^{10}$ and frequencies approaching $1$ GHz. The corresponding $Q \times f$ products make these devices several orders of magnitude better than any other mechanical system cooled to near the ground state. Such results are achieved for very-high overtones (up to 227th) of the longitudinally polarized phonons, such high overtones have never been observed previously. We discuss the basic requirements to achieve the extremely high quality factor regimes in acoustic devices by describing the main sources of losses. This includes material (two-level system, thermoelastic, Landau-Rumer losses), surface scattering, acoustic version of Raleigh scattering, clamping (phonon tunneling to the environment) loss mechanisms. Several types of BAW quartz resonators are compared. Finally, we discuss a range of applications of extremely low-loss acoustic cavities and how the very narrow bandwidths of the cavities (of orders of tens of $mHz$) can be incorporated into hybrid quantum systems. [Preview Abstract] |
Friday, March 7, 2014 9:24AM - 9:36AM |
Y34.00008: Strong acoustic coupling to a superconducting qubit Martin Gustafsson, Thomas Aref, Anton Frisk Kockum, Maria Ekstr\"om, G\"oran Johansson, Per Delsing Micromechanical resonators can be used to store quantum information, as shown in several recent experiments. These resonators typically have the form of membranes or beams, and phonons are localized to their vibrational eigenmodes. We present a different kind of mechanical quantum device, where \emph{propagating} phonons serve as carriers for quantum information. At the core of our device is a superconducting qubit, designed to couple to Surface Acoustic Waves (SAW) in the underlying substrate through the piezoelectric effect. This type of coupling can be very strong, and in our case exceeds the coupling to any external electromagnetic modes. The acoustic waves propagate freely on the surface of the substrate, and we use a remote electro-acoustic transducer to address the qubit acoustically and listen to its emission of phonons. This presentation focuses on the basic properties of our acoustic quantum system, and we include experimental data that demonstrate the quantized coupling between the qubit and the propagating acoustic waves. [Preview Abstract] |
Friday, March 7, 2014 9:36AM - 9:48AM |
Y34.00009: Acoustic equivalents of experiments from quantum optics Thomas Aref, Martin Gustafsson, Anton Kockum, Maria Ekstr\"om, G\"oran Johansson, Per Delsing On-chip quantum optics at microwave frequencies is a recent development, where solid-state qubits couple to itinerant photons in a one-dimensional electrical transmission line. We have demonstrated a new electromechanical hybrid, where a superconducting qubit couples to Surface Acoustic Waves (SAW), which propagate freely on the surface of piezoelectric microchip. This allows us to perform direct equivalents of quantum-optical experiments, with acoustic phonons taking over the role of photons as carriers of quantum information. We can address the qubit both electrically and with SAW, and listen to its quantized acoustic emission with an on-chip mechanical transducer. Our experiments are done at microwave frequencies, and compared to electromagnetic signals, the acoustic waves propagate orders of magnitude slower and have correspondingly shorter wavelengths. This, along with the potential for very strong coupling via the piezoelectric effect, opens for phononic exploration of quantum regimes that are difficult or impossible to reach with photons. In this talk, we present data from acoustic quantum experiments, with a focus on the prospective future role of propagating phonons in quantum informatics. [Preview Abstract] |
Friday, March 7, 2014 9:48AM - 10:00AM |
Y34.00010: Control and measurement of an optomechanical system using a superconducting qubit Florent Lecocq, John Teufel, Michael Allman, Katarina Cicak, Fabio Da Silva, Adam Sirois, Jed Whittaker, Jose Aumentado, Raymond Simmonds In cavity optomechanics one can use photons to manipulate and measure the mechanical motion of a macroscopic object. With these techniques, ground state cooling of a mechanical resonator [1] and coherent transfer between a state of light and mechanical motion have been demonstrated [2]. So far these experiments have been using Gaussian resources, and therefore are limited to the observation of Gaussian states. I will discuss recent experiments that use an artificial atom as a non-linear resource for cavity optomechanics. The device consists of a superconducting phase qubit coupled to a lumped element microwave cavity, whose capacitance is formed by a mechanically compliant vacuum-gap capacitor. The motion of the mechanical resonator is encoded in the intra-cavity microwave field. The cavity can thus mediate an interaction between the qubit and the mechanical resonator, enabling preparation and readout of non-classical states of motion. In this talk I will show how we use the qubit to measure of the time evolution of the photon distribution in the microwave cavity, allowing us to infer the phonon distribution in the mechanical resonator. [1] Teufel et al, Nature 475, 359 (2011) [2] Palomaki et al, Nature 495, 210 (2013) [Preview Abstract] |
Friday, March 7, 2014 10:00AM - 10:12AM |
Y34.00011: Entangling Mechanical Motion with Microwave Fields Tauno Palomaki, John Teufel, Raymond Simmonds, Konrad Lehnert We demonstrate entanglement between the motion of a mechanical oscillator and a propagating microwave field. The mechanical oscillator is coupled to a microwave resonator such that by applying a pump we can realize either a beam-splitter or parametric down-conversation interaction. We exploit both interactions to create two microwave pulses that are sufficiently correlated to be in an inseparable state. As the second pulse encodes the state of the mechanical oscillator, the first microwave pulses was consequently entangled with the mechanical oscillator. This result further demonstrates the potential for mechanical oscillators to both store and generate quantum mechanically useful states. [Preview Abstract] |
Friday, March 7, 2014 10:12AM - 10:24AM |
Y34.00012: Nonclassical State Revealed in a Fully Classical Harmonic System Wayne Huang In 1947, the measurement of Lamb and Retherford on the hyperfine spectrum of the hydrogen atom gave the first experimental evidence of the electromagnetic vacuum field. The interaction between matter and the vacuum field has since become an important topic in fundamental quantum electrodynamics. In this presentation, I would like to first discuss the excitation spectrum of a classical harmonic oscillator immersed in the vacuum field. Both our numerical simulation and perturbation analysis indicate that such a classical system exhibits the same excitation spectrum as its quantum counterpart. Then, I would like to show preliminary results on realizing the ``non-classical states'' within such a classical scheme. Namely, upon excitation the classical harmonic oscillator in the vacuum field displays interesting dynamical properties that are analogous to a coherent state, a squeezed state, and a Schrodinger cat state of a quantized light field. The intriguing connection between the classical harmonic system and the quantized light field may find application in the generation of nonclassical light using nano/optomechanical systems. [Preview Abstract] |
Friday, March 7, 2014 10:24AM - 10:36AM |
Y34.00013: Mechanically mediated amplification of microwave fields at the quantum limit John Teufel, Florent Lecocq, Raymond Simmonds, Jose Aumentado In cavity opto- and electro-mechanical devices, the parametric interaction between the electromagnetic and mechanical modes can strongly modify both the motional degree of freedom and the light field emerging from the cavity. For example, by driving the cavity at the sum frequency of the two modes, one naturally amplifies both the light and the motion. Unfortunately, in this method of operation, the finite linewidth and temperature of the mechanical mode limit the gain-bandwidth product and the added noise, respectively. Here we use a microwave optomechanical circuit to demonstrate experimentally a novel form of parametric amplification that goes beyond these traditional limits. In order to quantify the ideality of the microwave amplification, we integrate a normal-metal tunnel junction as an in situ, calibrated noise source. In this way, we demonstrate parametric gain in excess of 80 dB and show that the amplification process adds only the minimum noise required by quantum mechanics. [Preview Abstract] |
Friday, March 7, 2014 10:36AM - 10:48AM |
Y34.00014: Nanomechanical quantum many-body phonon-qubit systems for quantum simulators Oney Soykal, Charles Tahan We investigate nanomechanical systems consisting of arrays of coupled phonon cavities each including an impurity qubit in silicon. These experimentally feasible architectures can exhibit quantum many-body phase transitions, e.g. Mott insulator and superfluid states, due to a strong phonon-phonon interaction, and are suitable in the pursuit of quantum simulators. We investigate driven dissipative non-equilibrium systems at zero and non-zero temperatures. These quantum many-body phonon systems can be implemented using either on-chip nano mechanical systems in silicon or DBR heterostructures in silicon-germanium. We examine the experimental procedures to detect these states and show that temperature and driving field (write/read-out) play a critical role in achieving these phonon superfluid and insulator states. These many-body cavity phonon/qubit systems with strong phonon-phonon interactions can be used in forming truly quantum many-body mechanical states for quantum simulators as well as to complement other nano/optomechanical systems. [Preview Abstract] |
Friday, March 7, 2014 10:48AM - 11:00AM |
Y34.00015: An Optomechanical Transducer for Microwave to Optical Quantum State Transfer A. Vainsencher, J. Bochmann, G. Peairs, K.J. Satzinger, D.D. Awschalom, A.N. Cleland Recent experiments have demonstrated that macroscopic optomechanical systems can be operated in the quantum regime\footnote{Safavi-Naeini et al. Phys. Rev. Lett. \textbf{108}, 033602 (2012)}\footnote{Teufel et al. \textit{Nature} \textbf{475}, 359 (2011)}\footnote{Chan et al. \textit{Nature} \textbf{478}, 89 (2011)}. Such systems offer a wide range of possibilities for new applications, potentially enabling coupling between disparate quantum systems. In this talk, we will describe our approach to using an optomechanical system as a microwave to optical transducer, with the eventual goal of coupling superconducting quantum bits to a light field. Our implementation uses an optomechanical crystal made of aluminum nitride, a strong piezoelectric. This choice of design and material offers the necessary optomechanical and electromechanical coupling rates that should make quantum state transfer possible. We will present recent results for our transducer concept, including classical operation\footnote{Bochmann, Vainsencher et al. \textit{Nature Physics} \textbf{9}, 712 (2013)}, design improvements, and cryogenic operation. [Preview Abstract] |
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