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Articles 1 - 12 of 12
Full-Text Articles in Physics
Damping And Decoherence Of A Nanomechanical Resonator Due To A Few Two-Level Systems, Laura G. Remus, Miles P. Blencowe, Yukihiro Tanaka
Damping And Decoherence Of A Nanomechanical Resonator Due To A Few Two-Level Systems, Laura G. Remus, Miles P. Blencowe, Yukihiro Tanaka
Dartmouth Scholarship
We consider a quantum model of a nanomechanical flexing beam resonator interacting with a bath comprising a few damped tunneling two-level systems. In contrast with a resonator interacting bilinearly with an ohmic free oscillator bath (modeling clamping loss, for example), the mechanical resonator damping is amplitude dependent, while the decoherence of quantum superpositions of mechanical position states depends only weakly on their spatial separation.
On The Use Of The Proximity Force Approximation For Deriving Limits To Short-Range Gravitational-Like Interactions From Sphere-Plane Casimir Force Experiments, Diego A. R. Dalvit, Roberto Onofrio
On The Use Of The Proximity Force Approximation For Deriving Limits To Short-Range Gravitational-Like Interactions From Sphere-Plane Casimir Force Experiments, Diego A. R. Dalvit, Roberto Onofrio
Dartmouth Scholarship
We discuss the role of the proximity force approximation in deriving limits to the existence of Yukawian forces—predicted in the submillimeter range by many unification models—from Casimir force experiments using the sphere-plane geometry. Two forms of this approximation are discussed, the first used in most analyses of the residuals from the Casimir force experiments performed so far, and the second recently discussed in this context in R. Decca et al. [Phys. Rev. D 79, 124021 (2009)]. We show that the former form of the proximity force approximation overestimates the expected Yukawa force and that the relative deviation …
Dynamical Quantum Error Correction Of Unitary Operations With Bounded Controls, Kaveh Khodjasteh, Lorenza Viola
Dynamical Quantum Error Correction Of Unitary Operations With Bounded Controls, Kaveh Khodjasteh, Lorenza Viola
Dartmouth Scholarship
Dynamically corrected gates were recently introduced [K. Khodjasteh and L. Viola, Phys. Rev. Lett. 102, 080501 (2009)] as a tool to achieve decoherence-protected quantum gates based on open-loop Hamiltonian engineering. Here, we further expand the framework of dynamical quantum error correction, with emphasis on elucidating under what conditions decoherence suppression can be ensured while performing a generic target quantum gate, using only available bounded-strength control resources. Explicit constructions for physically relevant error models are detailed, including arbitrary linear decoherence and pure dephasing on qubits. The effectiveness of dynamically corrected gates in an illustrative non-Markovian spin-bath setting is investigated numerically, …
Anomalous Nonergodic Scaling In Adiabatic Multicritical Quantum Quenches, Shusa Deng, Gerardo Ortiz, Lorenza Viola
Anomalous Nonergodic Scaling In Adiabatic Multicritical Quantum Quenches, Shusa Deng, Gerardo Ortiz, Lorenza Viola
Dartmouth Scholarship
We investigate non-equilibrium dynamical scaling in adiabatic quench processes across quantum multi critical points. Our analysis shows that the resulting power-law scaling depends sensitively on the control path, and that anomalous critical exponents may emerge depending on the universality class. We argue that the observed anomalous behavior originates in the fact that the dynamical excitation process takes place asymmetrically with respect to the static multicritical point, and that non-critical energy modes may play a dominant role. As a consequence, dynamical scaling requires introducing new non-static exponents.
Analogue Hawking Radiation In A Dc-Squid Array Transmission Line, P D. Nation, M. P. Blencowe, A. J. Rimberg, E. Buks
Analogue Hawking Radiation In A Dc-Squid Array Transmission Line, P D. Nation, M. P. Blencowe, A. J. Rimberg, E. Buks
Dartmouth Scholarship
We propose the use of a superconducting transmission line formed from an array of dc-SQUID’s for investigating analogue Hawking radiation. Biasing the array with a space-time varying flux modifies the propagation velocity of the transmission line, leading to an effective metric with an horizon. Being a fundamentally quantum mechanical device, this setup allows for investigations of quantum effects such as back-reaction and analogue space-time fluctuations on the Hawking process.
Hydrodynamic Relaxation Of An Electron Plasma To A Near-Maximum Entropy State, D. J. Rodgers, S. Servidio, W. H. Matthaeus, D. C. Montgomery, T. B. Mitchell, T. Aziz
Hydrodynamic Relaxation Of An Electron Plasma To A Near-Maximum Entropy State, D. J. Rodgers, S. Servidio, W. H. Matthaeus, D. C. Montgomery, T. B. Mitchell, T. Aziz
Dartmouth Scholarship
Dynamical relaxation of a pure electron plasma in a Malmberg-Penning trap is studied, comparing experiments, numerical simulations and statistical theories of weakly dissipative two-dimensional (2D) turbulence. Simulations confirm that the dynamics are approximated well by a 2D hydrodynamic model. Statistical analysis favors a theoretical picture of relaxation to a near-maximum entropy state with constrained energy, circulation, and angular momentum. This provides evidence that 2D electron fluid relaxation in a turbulent regime is governed by principles of maximum entropy.
Intermodulation And Parametric Amplification In A Superconducting Stripline Resonator Integrated With A Dc-Squid, B. Abdo, O. Suchoi, E. Segev, O. Shtempluck, M. Blencowe, E. Buks
Intermodulation And Parametric Amplification In A Superconducting Stripline Resonator Integrated With A Dc-Squid, B. Abdo, O. Suchoi, E. Segev, O. Shtempluck, M. Blencowe, E. Buks
Dartmouth Scholarship
We utilize a superconducting stripline resonator containing a dc-SQUID as a strong intermodulation amplifier exhibiting a signal gain of 24dB and a phase modulation of 30dB. Studying the system response in the time domain near the intermodulation amplification threshold reveals a unique noise-induced spikes behavior. We account for this response qualitatively via solving numerically the equations of motion for the integrated system. Furthermore, employing this device as a parametric amplifier yields an abrupt rise of 38dB in the generated side-band signal.
Auroral Evidence For Multiple Reconnection In The Magnetospheric Tail Plasma Sheet, R. A. Treumann, C. H. Jaroschek, R. Pottelette
Auroral Evidence For Multiple Reconnection In The Magnetospheric Tail Plasma Sheet, R. A. Treumann, C. H. Jaroschek, R. Pottelette
Dartmouth Scholarship
We present auroral evidence for multiple and, most probably, small-scale reconnection in the near-Earth magnetospheric plasma sheet current layer during auroral activity. Hall currents as the source of upward and downward field-aligned currents require the generation of the corresponding electron fluxes. The auroral spatial ordering in a multiple sequence of these fluxes requires the assumption of the existence of several —and possibly— even many tailward reconnection sites.
Field Line Distribution Of Density At L=4.8 Inferred From Observations By Cluster, R E. Denton, P Décréau, M J. Engebretson, F Darrouzet
Field Line Distribution Of Density At L=4.8 Inferred From Observations By Cluster, R E. Denton, P Décréau, M J. Engebretson, F Darrouzet
Dartmouth Scholarship
For two events observed by the CLUSTER space- craft, the field line distribution of mass density ρ was inferred from Alfve ́n wave harmonic frequencies and compared to the electron density ne from plasma wave data and the oxy- gen density nO+ from the ion composition experiment. In one case, the average ion mass M≡ρ/ne was about 5amu (28 October 2002), while in the other it was about 3 amu (10 September 2002). Both events occurred when the CLUSTER 1 (C1) spacecraft was in the plasmatrough. Nevertheless, the electron density ne was significantly lower for the first event (ne =8 …
Dynamically Error-Corrected Gates For Universal Quantum Computation, Kaveh Khodjasteh, Lorenza Viola
Dynamically Error-Corrected Gates For Universal Quantum Computation, Kaveh Khodjasteh, Lorenza Viola
Dartmouth Scholarship
Scalable quantum computation in realistic devices requires that precise control can be implemented efficiently in the presence of decoherence and operational errors. We propose a general constructive procedure for designing robust unitary gates on an open quantum system without encoding or measurement overhead. Our results allow for a low-level err or correction strategy solely based on Hamiltonian engineering using realistic bounded-strength controls and may substantially reduce implementation requirements for fault-tolerant quantum computing architectures.
Class Of Nonperturbative Configurations In Abelian-Higgs Models: Complexity From Dynamical Symmetry Breaking, M. Gleiser, J. Thorarinson
Class Of Nonperturbative Configurations In Abelian-Higgs Models: Complexity From Dynamical Symmetry Breaking, M. Gleiser, J. Thorarinson
Dartmouth Scholarship
We present a numerical investigation of the dynamics of symmetry breaking in both Abelian and non-Abelian [SU(2)] Higgs models in three spatial dimensions. We find a class of time-dependent, long-lived nonperturbative field configurations within the range of parameters corresponding to type-1 superconductors, that is, with vector masses (mv) larger than scalar masses (ms). We argue that these emergent nontopological configurations are related to oscillons found previously in other contexts. For the Abelian-Higgs model, our lattice implementation allows us to map the range of parameter space—the values of β=(ms/mv)2—where such configurations exist and to follow them for times t∼O(105)m−1. An investigation …
Dynamical Non-Ergodic Scaling In Continuous Finite-Order Quantum Phase Transitions, S. Deng, G. Ortiz, L. Viola
Dynamical Non-Ergodic Scaling In Continuous Finite-Order Quantum Phase Transitions, S. Deng, G. Ortiz, L. Viola
Dartmouth Scholarship
We investigate the emergence of universal dynamical scaling in quantum critical spin systems adiabatically driven out of equilibrium, with emphasis on quench dynamics which involves non-isolated critical points (i.e., critical regions) and cannot be a priori described through standard scaling arguments nor time-dependent perturbative approaches. Comparing to the case of an isolated quantum critical point, we find that non-equilibrium scaling behavior of a large class of physical observables may still be explained in terms of equilibrium critical exponents. However, the latter are in general non-trivially path-dependent, and detailed knowledge about the time-dependent excitation process becomes essential. In particular, …