Generalized Feynman-vernon Approach To Dissipative Quantum Systems

In this paper the so-called Feynman-Vernon influence functional theory has been generalized in order to include the possibility of dealing with initial conditions of the system plus environment other than the factorizable one. It has been shown that the new influence functional can now be written in terms of paths which represent the coupling of quantum-statistical to quantum-dynamical effects. Once the thermal paths are integrated out of this new influence functional, a generalization of the original Feynman-Vernon expression is obtained. © 1987 The American Physical Society.3673509351

Single-Spin Measurement and Decoherence in Magnetic Resonance Force Microscopy

We consider a simple version of a cyclic adiabatic inversion (CAI) technique in magnetic resonance force microscopy (MRFM). We study the problem: What component of the spin is measured in the CAI MRFM? We show that the non-destructive detection of the cantilever vibrations provides a measurement of the spin component along the effective magnetic field. This result is based on numerical simulations of the Hamiltonian dynamics (the Schrodinger equation) and the numerical solution of the master equation.Comment: 5 pages + 5 figures (PNG format

New Model For Dissipation In Quantum Mechanics

We propose a new model for studying dissipation in quantum-mechanical systems. The mechanism of dissipation is solely due to the scattering of the environment excitations by the particle of interest. We treat the problem via the functional integral formalism. It is shown that the model gives a damping parameter which is temperature dependent.67151960196

Bosonization Approach For Bilayer Quantum Hall Systems At νt=1

We develop a nonperturbative bosonization approach for bilayer quantum Hall systems at νT=1, which allows us to systematically study the existence of an exciton condensate in these systems. An effective boson model is derived and the excitation spectrum is calculated in both the Bogoliubov and the Popov approximations. In the latter case, we show that the ground state of the system is an exciton condensate only when the distance between the layers is very small compared to the magnetic length, indicating that the system possibly undergoes another phase transition before the incompressible-compressible one. The effect of a finite electron interlayer tunneling is included and a quantitative phase diagram is proposed. © 2006 The American Physical Society.9718(1997) Perspectives in Quantum Hall Effects, , edited by S. Das Sarma and A. Pinczuk (Wiley, New York)Eisenstein, J.P., MacDonald, A.H., (2004) Nature (London), 432, p. 691. , NATUAS 0028-0836 10.1038/nature03081Eisenstein, J.P., (2004) Science, 305, p. 950. , SCIEAS 0036-8075 10.1126/science.1099386Murphy, S.Q., (1994) Phys. Rev. Lett., 72, p. 728. , PRLTAO 0031-9007 10.1103/PhysRevLett.72.728Girvin, S.M., cond-mat/0108181Spielman, I.B., (2000) Phys. Rev. Lett., 84, p. 5808. , PRLTAO 0031-9007 10.1103/PhysRevLett.84.5808Spielman, I.B., (2001) Phys. Rev. Lett., 87, p. 036803. , PRLTAO 0031-9007 10.1103/PhysRevLett.87.036803Fertig, H.A., Straley, J.P., (2003) Phys. Rev. Lett., 91, p. 046806. , PRLTAO 0031-9007 10.1103/PhysRevLett.91.046806Kellogg, M., (2004) Phys. Rev. Lett., 93, p. 036801. , PRLTAO 0031-9007 10.1103/PhysRevLett.93.036801Wiersma, R.D., (2004) Phys. Rev. Lett., 93, p. 266805. , PRLTAO 0031-9007 10.1103/PhysRevLett.93.266805Wen, X.G., Zee, A., (1992) Phys. Rev. Lett., 69, p. 1811. , PRLTAO 0031-9007 10.1103/PhysRevLett.69.1811Fertig, H.A., (1989) Phys. Rev. B, 40, p. 1087. , PRBMDO 0163-1829 10.1103/PhysRevB.40.1087MacDonald, A.H., (1990) Phys. Rev. Lett., 65, p. 775. , PRLTAO 0031-9007 10.1103/PhysRevLett.65.775Joglekar, Y.N., MacDonald, A.H., (2001) Phys. Rev. B, 64, p. 155315. , PRBMDO 0163-1829 10.1103/PhysRevB.64.155315Fertig, H.A., Murthy, G., (2005) Phys. Rev. Lett., 95, p. 156802. , PRLTAO 0031-9007 10.1103/PhysRevLett.95.156802Doretto, R.L., Caldeira, A.O., Girvin, S.M., (2005) Phys. Rev. B, 71, p. 045339. , PRBMDO 0163-1829 10.1103/PhysRevB.71.045339Kallin, C., Halperin, B.I., (1984) Phys. Rev. B, 30, p. 5655. , PRBMDO 0163-1829 10.1103/PhysRevB.30.5655Fetter, A.L., Walecka, J.D., (2003) Quantum Theory of Many-Particle Systems, , Dover, MineolaStoof, H.T.C., Bijlsma, M., (1993) Phys. Rev. E, 47, p. 939. , PLEEE8 1063-651X 10.1103/PhysRevE.47.939Shi, H., Griffin, A., (1998) Phys. Rep., 304, p. 1. , PRPLCM 0370-1573 10.1016/S0370-1573(98)00015-5Chen, X.M., Quinn, J.J., (1992) Phys. Rev. B, 45, p. 11054. , PRBMDO 0163-1829 10.1103/PhysRevB.45.1105

Limits Of Weak Damping Of A Quantum Harmonic Oscillator

In this Brief Report we analyze the limit of very weak damping of a quantum-mechanical Brownian oscillator. It is shown that the propagator for the reduced density operator of the oscillator can be written as a double path integral of the same form as that obtained in the high-temperature limit. As a direct consequence, we can write a Fokker-Planck equation for the reduced density operator of the weakly damped oscillator (at any temperature) involving only the damping and a generalized diffusion constant in momentum space. © 1989 The American Physical Society.4063438344

Transient Dynamics in Magnetic Force Microscopy for a Single-Spin Measurement

We analyze a single-spin measurement using a transient process in magnetic force microscopy (MFM) which could increase the maximum operating temperature by a factor of Q (the quality factor of the cantilever) in comparison with the static Stern-Gerlach effect. We obtain an exact solution of the master equation, which confirms this result. We also discuss the conditions required to create a macroscopic Schrodinger cat state in the cantilever.Comment: 22 pages 2 figure

Quantum Dissipative Dynamics of the Magnetic Resonance Force Microscope in the Single-Spin Detection Limit

We study a model of a magnetic resonance force microscope (MRFM) based on the cyclic adiabatic inversion technique as a high-resolution tool to detect single electron spins. We investigate the quantum dynamics of spin and cantilever in the presence of coupling to an environment. To obtain the reduced dynamics of the combined system of spin and cantilever, we use the Feynman-Vernon influence functional and get results valid at any temperature as well as at arbitrary system-bath coupling strength. We propose that the MRFM can be used as a quantum measurement device, i.e., not only to detect the modulus of the spin but also its direction

Application Of The Generalized Feynman-vernon Approach To A Simple System: The Damped Harmonic Oscillator

We apply a recently developed generalization of the Feynman-Vernon approach to the case of a quantum-mechanical damped oscillator. We develop a variational method to treat the path integral that controls the dynamics of the reduced density operator of the system once it is subject to an arbitrary initial condition. The method is completely independent of the specific symmetries involved in the problem. Although we have applied it particularly to the harmonic oscillator, we believe it could be extended to more complex systems. © 1990 The American Physical Society.4163103311

Quantum tunneling in a Kerr medium with parametric pumping

A quantum optical model with a classical phase space exhibiting nonlinear oscillations around two elliptic fixed points is investigated. The quantum system is found to display coherent tunneling between near coherent states of opposite phase centered at the classical fixed points

Universal asymptotic behavior in flow equations of dissipative systems

Based on two dissipative models, universal asymptotic behavior of flow equations for Hamiltonians is found and discussed. Universal asymptotic behavior only depends on fundamental bath properties but not on initial system parameters, and the integro-differential equations possess an universal attractor. The asymptotic flow of the Hamiltonian can be characterized by a non-local differential equation which only depends on one parameter - independent of the dissipative system or truncation scheme. Since the fixed point Hamiltonian is trivial, the physical information is completely transferred to the transformation of the observables. This yields a more stable flow which is crucial for the numerical evaluation of correlation functions. Furthermore, the low energy behavior of correlation functions is determined analytically. The presented procedure can also be applied if relevant perturbations are present as is demonstrated by evaluating dynamical correlation functions for sub-Ohmic environments. It can further be generalized to other dissipative systems.Comment: 15 pages, 9 figures; to appear in Phys. Rev.