Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session Y15: Focus Session: Quantum Metrology and Control: Fundamental Limits and Applications |
Hide Abstracts |
Sponsoring Units: GQI Chair: Lorenza Viola, Dartmouth College Room: Morial Convention Center 207 |
Friday, March 14, 2008 11:15AM - 11:51AM |
Y15.00001: Quantum Enhanced Sensing, Measurement, and Control Invited Speaker: Seth Lloyd This talk investigates how quantum-mechanical effects such as squeezing and entanglement can be used to enhance the precision and sensitivity of imaging, measurement, and control. Entanglement can give a substantial enhancement to sensitivity even in the presence of high levels of noise and loss. [Preview Abstract] |
Friday, March 14, 2008 11:51AM - 12:03PM |
Y15.00002: Environmental Constraints in Practical Photonic Quantum Sensing. Yaakov Weinstein, Gerald Gilbert, Michael Hamrick We report on research directed to problems associated with the propagation of photonic signal states in quantum sensing. Attention is devoted to constraints associated to realistic propagation environments for practical applications of quantum sensing. [Preview Abstract] |
Friday, March 14, 2008 12:03PM - 12:15PM |
Y15.00003: Quantum efficiency of binary-outcome solid-state detectors Alexander N. Korotkov We discuss the definitions of the quantum efficiency for binary-output detectors of solid-state qubits, focusing on the subclass of quantum non-demolition detectors. Similar to the previously considered case of linear detectors, the definitions of the quantum efficiency are based on the relation between the ensemble decoherence and the information acquired from the measurement (this information determines the lower bound for the ensemble decoherence). Quantum efficiency is analyzed for several models of binary-outcome detectors, including indirect projective measurement, linear detector in a binary-output regime, detector for a phase qubit, and detector based on tunneling into continuum. [Preview Abstract] |
Friday, March 14, 2008 12:15PM - 12:27PM |
Y15.00004: Quantum Metrology with Product States Animesh Datta, Sergio Boixo, Steven Flammia, Anil Shaji, Carlton Caves, Emilio Bagan We study the performance of initial product states of $n$-body systems in generalized quantum metrology protocols that involve estimating an unknown coupling constant in a nonlinear k-body ($k \ll n$) Hamiltonian. We obtain the theoretical lower bound on the uncertainty in the estimate of the parameter. For arbitrary initial states, the lower bound scales as $1/n^k$, and for initial product states, it scales as $1/n^{k-1/2}$. We show that the latter scaling can be achieved using simple, separable measurements. We formulate a simple model, based on the evolution of angular-momentum coherent states, which explains the $O(n^{-3/2})$ scaling for $k = 2$, implementable with Bose-Einstein condensates; the model shows that the entanglement generated by the quadratic Hamiltonian does not play a role in the enhanced sensitivity scaling. We show that phase decoherence does not affect the $O(n^{-3/2})$ sensitivity scaling for initial product states. [Preview Abstract] |
Friday, March 14, 2008 12:27PM - 12:39PM |
Y15.00005: Efficient feedback controllers for continuous-time quantum error correction Andrew Landahl, Brad Chase, J.M. Geremia We present an efficient approach to continuous-time quantum error correction that extends the low-dimensional quantum filtering methodology developed by van Handel and Mabuchi [quant-ph/0511221 (2005)] to include error recovery operations in the form of real-time quantum feedback. We expect this paradigm to be useful for systems in which error recovery operations cannot be applied instantaneously. While we could not find an exact low-dimensional filter that combined both continuous syndrome measurement and a feedback Hamiltonian appropriate for error recovery, we developed an approximate reduced-dimensional model to do so. Simulations of the five-qubit code subjected to the symmetric depolarizing channel suggests that error correction based on our approximate filter performs essentially identically to correction based on an exact quantum dynamical model. [Preview Abstract] |
Friday, March 14, 2008 12:39PM - 12:51PM |
Y15.00006: Passive Cooling of a Micromechanical Oscillator with a Resonant Electric Circuit K.R. Brown, J. Britton, R.J. Epstein, J. Chiaverini, D. Leibfried, D.J. Wineland Currently there is considerable interest in the cooling of macroscopic mechanical oscillators, as strong cooling may allow one to reach the quantum regime of such oscillators. Recent advances in fabrication and cooling techniques have brought this regime much closer. Here we present theoretical and experimental results for cooling of the fundamental mode of a miniature cantilever by capacitively coupling it to a driven rf resonant circuit. Cooling results from the rf capacitive force, which is phase shifted relative to the cantilever motion due to the finite decay time of the resonant circuit. If this force varies with an appropriate phase shift relative to the motion of the cantilever, it can oppose the velocity of the cantilever, leading to cooling. We demonstrate this technique by cooling a 7 kHz cantilever from room temperature to 45 K, obtaining reasonable agreement with a model for the cooling, damping, and frequency shift. Extending the method to higher frequencies in a cryogenic system could enable ground state cooling and may prove simpler than related optical experiments in a low temperature apparatus. [Preview Abstract] |
Friday, March 14, 2008 12:51PM - 1:03PM |
Y15.00007: Sensitive orthogonal optical monitoring of a micromechanical oscillator Ako Chijioke, John Lawall Optical sensing of oscillations of a mechanical microresonator is of crucial interest for a number of purposes including observation of quantum behavior of macroscopic objects and force microscopy. The majority of optical sensing schemes use light aligned with the axis of mechanical oscillation. We present sensitive monitoring of the oscillations of a micromechanical resonator orthogonal to the field in an optical cavity, and its particular advantages. [Preview Abstract] |
Friday, March 14, 2008 1:03PM - 1:15PM |
Y15.00008: Sideband Resolved Cooling of a Nanomechanical Resonator Parametrically Coupled to a Microwave Resonator Jared Hertzberg, Tristan Rocheleau, Tchefor Ndukum, Keith Schwab We have created a nanostructure formed by a radio-frequency nanomechanica (NEMS) resonator capacitively coupled to a 5 GHz superconducting, co-planar waveguide (CPW) resonator. Recently, we have shown that it is possible to passively cool a NEMS resonator to within a few tens of quanta of its ground state, N = 25 [1]. By driving this coupled system at a frequency $\omega_{pump} = \omega_{CPW} - \omega_{NEMS}$, we expect to produce an active cooling process in the sideband resolved limit which in principle [2] should be capable of preparing the ground state of motion,with occupation factors N << 1. In future work, we expect to be able to demonstrate backaction evading position detection and ultimately squeezed quantum states of the mechanical device by using more advanced pumping schemes, such as double sideband pumping. [1] A. Naik et al, Nature 443, 193 - 196 (2006) [2] F. Marquardt et al, Phys. Rev. Lett. 99, 093902 (2007) [Preview Abstract] |
Friday, March 14, 2008 1:15PM - 1:27PM |
Y15.00009: Parametric Amplification of Quantum Signals with a Josephson Ring Modulator Nicolas Bergeal, Flavius Schakert, Michael Metcalfe, Vladimir Manucharyan, Rajamani Vijayaraghavan, Markus Brink, Michel Devoret Quantum Mechanics puts a limit on how small the degradation of information passing through a phase preserving amplifier can be. It is known theoretically that the minimum noise added by the amplifier to the signal amounts at least to half a photon at the signal frequency.~ Is it possible~to construct a~practical amplifier working at microwave frequencies that would reach this quantum limit? We have developed a new device aiming at answering this question, which is of practical importance for the readout of solid state qubits, and more generally, for the measurement of very weak signals in various areas of science. The device is based on a ring of four Josephson junctions which connects two microwave resonators corresponding to the signal and idler modes. It can be operated both as an amplifier and a frequency converter. Theoretical aspects and experimental results will be presented. [Preview Abstract] |
Friday, March 14, 2008 1:27PM - 1:39PM |
Y15.00010: Microwave characterization of Josephson junction arrays in superconducting regime for Coulomb blockade and quantum metrology Vladimir Manucharyan, Michael Metcalfe, Jens Koch, Luigi Frunzio, Markus Brink, Nicolas Bergeal, Leonid Glazman, Michel Devoret Although the phenomenon of Bloch Oscillations could in principle lead to a primary standard of electrical current, it requires in practice the embedding of a Josephson junction in an electrodynamic environment with microwave impedance much greater than resistance quantum for Cooper pairs. A promising candidate for such environment is an array of Josephson tunnel junctions in the superconducting (non-insulating) regime. We have developed a new technique to dispersively probe the electromagnetic properties of such arrays. We access the RF impedance of the array by placing it as a ``mirror'' in a high-Q planar superconducting microwave resonator, whose phase and magnitude response are measured. The advantage of this configuration is that, while measuring the RF property of the array, we can pass DC current through it. This serves three purposes: i) emulating the situation of a current standard experiment with arrays, ii) providing a knob for control experiments on the RF dissipation in arrays, iii) exploring a novel out-of-equilibrium non-linear collective system. Our experiment also contributes to the physics of superconducting qubits and nano-wires. [Preview Abstract] |
Friday, March 14, 2008 1:39PM - 1:51PM |
Y15.00011: Impact of Atomic Gap Size on Sensitivity and Backaction of APC Displacement Detectors N.E. Flowers-Jacobs, K.W. Lehnert Recently our group created a mesoscopic displacement detector formed by coupling an atomic point contact (APC) to a nanomechanical beam and demonstrated a displacement imprecision limited by the fundamental shot-noise in the number of electrons that tunnel across the APC [1]. We continue this work by using a cryogenic apparatus that flexes the device substrate to mechanically adjust the size of the APC atomic gap {\it in situ}. The resulting changes in the APC displacement detector's intrinsic noise properties are measured by observing the 1 K random thermal motion of the nanomechanical beam at resonance frequencies up to 200 MHz. The goal of this work is to explore the effect of atomic gap size and shape on displacement sensitivity, understand the origin of the observed measurement backaction, and measure the recoil force of tunneling electrons. \newline \newline [1] N. E. Flowers-Jacobs, D. R. Schmidt, and K. W. Lehnert, {\it Phys. Rev. Lett.} {\bf 98}, 096804 (2007) [Preview Abstract] |
Friday, March 14, 2008 1:51PM - 2:03PM |
Y15.00012: Quantum Zeno Effect in Detection of Itinerant Microwave Photons Ferdinand Helmer, Matteo Mariantoni, Enrique Solano, Florian Marquardt We analyze detection of itinerant photons using a QND measurement. We show that the backaction due to the continuous measurement poses a fundamental limit for the fidelity of detection in such a scheme. We illustrate this using a setup where signal photons have to enter a cavity in order to be detected dispersively. The measurement signal in this approach is the phase shift imparted to an intense beam passing through a second cavity mode. The restrictions on the fidelity are a consequence of the Quantum Zeno effect, and we discuss both analytical results and quantum trajectory simulations of the measurement process. Finally, we briefly mention a possible experimental realisation in the context of superconducting circuit QED. [Preview Abstract] |
Friday, March 14, 2008 2:03PM - 2:15PM |
Y15.00013: Rapid Purification protocols for Optical Homodyning Aravind Chiruvelli Recently Jacobs (PRA 67 030301 (2003)) and Wiseman and Ralph (New J. Phys 8, 90(2006)) have discovered rapid purification protocols for a qubit using quantum feedback. We present these protocols in optical setting. These could also be very useful in quantum state preparation for various uses in metrology and control. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2021 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
1 Research Road, Ridge, NY 11961-2701
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700