Universal dynamical control of decay and decoherence for weak and strong system-bath coupling

2005 ◽  
Vol 5 (4&5) ◽  
pp. 285-317
Author(s):  
G. Gordon ◽  
G. Kurizki ◽  
A.G. Kofman ◽  
S. Pellegrin
Keyword(s):  
Random Phase ◽  
Quantum Systems ◽  
Unified Theory ◽  
Phase Fluctuations ◽  
Strongly Coupled ◽  
Weakly Coupled ◽  
Abrupt Changes ◽  
Dynamical Control ◽  
Strong System ◽  
The Continuum

A unified theory is given of dynamically modified decay and decoherence in driven two-level and multilevel quantum systems that are weakly coupled to arbitrary finite-temperature reservoirs and undergo random phase fluctuations. Criteria for the optimization of decoherence suppression and the limitations of this approach are obtained. For a driven qubit that is strongly coupled to the continuum edge of reservoir's spectrum, we demonstrate that only an appropriately ordered sequence of abrupt changes of the resonance frequency, near the continuum edge, can effectively protect the qubit state from decoherence.

scholarly journals A Green’s function perspective on the nonequilibrium thermodynamics of open quantum systems strongly coupled to baths

2021 ◽  
Author(s):  
Nicolas Bergmann ◽  
Michael Galperin
Keyword(s):  
Green’S Function ◽  
Quantum Transport ◽  
Green's Function ◽  
Nonequilibrium Thermodynamics ◽  
Open Quantum Systems ◽  
Quantum Systems ◽  
Thermodynamic Consideration ◽  
Strongly Coupled ◽  
Open Quantum ◽  
Weakly Coupled

AbstractWe give a nonequilibrium Green’s function (NEGF) perspective on thermodynamics formulations for open quantum systems that are strongly coupled to baths. A scattering approach implying thermodynamic consideration of a supersystem (system plus baths) that is weakly coupled to external superbaths is compared with the consideration of thermodynamics of a system that is strongly coupled to its baths. We analyze both approaches from the NEGF perspective and argue that the latter yields a possibility of thermodynamic formulation consistent with a dynamical (quantum transport) description.

scholarly journals Fundamental limitations of the mode temperature concept in strongly coupled systems

2020 ◽  
Vol 75 (8) ◽  
pp. 803-807
Author(s):  
Svend-Age Biehs ◽  
Achim Kittel ◽  
Philippe Ben-Abdallah
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Strong Coupling ◽  
Quantum Systems ◽  
Coupled Systems ◽  
Strong Coupling Limit ◽  
Strongly Coupled ◽  
Fundamental Limitations ◽  
Temperature Concept ◽  
Vacuum Gap

AbstractWe theoretically analyze heat exchange between two quantum systems in interaction with external thermostats. We show that in the strong coupling limit the widely used concept of mode temperatures loses its thermodynamic foundation and therefore cannot be employed to make a valid statement on cooling and heating in such systems; instead, the incorrectly applied concept may result in a severe misinterpretation of the underlying physics. We illustrate these general conclusions by discussing recent experimental results reported on the nanoscale heat transfer through quantum fluctuations between two nanomechanical membranes separated by a vacuum gap.

scholarly journals CFT unitarity and the AdS Cutkosky rules

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
David Meltzer ◽  
Allic Sivaramakrishnan
Keyword(s):  
Flat Space ◽  
Tree Level ◽  
Optical Theorem ◽  
Conformal Field Theories ◽  
Strongly Coupled ◽  
Conformal Field ◽  
Weakly Coupled ◽  
S Matrix ◽  
Space Limit ◽  
Diagrammatic Method

Abstract We derive the Cutkosky rules for conformal field theories (CFTs) at weak and strong coupling. These rules give a simple, diagrammatic method to compute the double-commutator that appears in the Lorentzian inversion formula. We first revisit weakly-coupled CFTs in flat space, where the cuts are performed on Feynman diagrams. We then generalize these rules to strongly-coupled holographic CFTs, where the cuts are performed on the Witten diagrams of the dual theory. In both cases, Cutkosky rules factorize loop diagrams into on-shell sub-diagrams and generalize the standard S-matrix cutting rules. These rules are naturally formulated and derived in Lorentzian momentum space, where the double-commutator is manifestly related to the CFT optical theorem. Finally, we study the AdS cutting rules in explicit examples at tree level and one loop. In these examples, we confirm that the rules are consistent with the OPE limit and that we recover the S-matrix optical theorem in the flat space limit. The AdS cutting rules and the CFT dispersion formula together form a holographic unitarity method to reconstruct Witten diagrams from their cuts.

scholarly journals Prandtl Number in Classical Hard-Sphere and One-Component Plasma Fluids

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 821
Author(s):  
Sergey Khrapak ◽  
Alexey Khrapak
Keyword(s):  
Prandtl Number ◽  
Hard Sphere ◽  
Solid Phase ◽  
Freezing Point ◽  
Three Dimensional ◽  
Order Unity ◽  
Strongly Coupled ◽  
Dielectric Fluids ◽  
Weakly Coupled ◽  
Component Plasma

The Prandtl number is evaluated for the three-dimensional hard-sphere and one-component plasma fluids, from the dilute weakly coupled regime up to a dense strongly coupled regime near the fluid-solid phase transition. In both cases, numerical values of order unity are obtained. The Prandtl number increases on approaching the freezing point, where it reaches a quasi-universal value for simple dielectric fluids of about ≃1.7. Relations to two-dimensional fluids are briefly discussed.

Article

1999 ◽  
Vol 77 (11) ◽  
pp. 1810-1812 ◽  
Author(s):  
Alex D Bain
Keyword(s):  
Spin System ◽  
Coupled System ◽  
Coupled Systems ◽  
Physical Reason ◽  
Strongly Coupled ◽  
System Combination ◽  
First Order ◽  
Weakly Coupled ◽  
Quantum Transitions ◽  
Weakly Coupled Systems

Strongly coupled spin systems provide many curious and interesting effects in NMR spectra, one of which is the presence of unexpected (from a first-order viewpoint) lines. A physical reason is given for the presence of these combination lines. The X part of the spectrum of an ABX spin system is analysed as an example. For an ABX system, it is well known that the AB nuclei give a spectrum consisting of two AB-type spectra, corresponding to the two orientations of the X nucleus. It can also be shown that the X part of the spectrum corresponds to the X nucleus undergoing a transition in the presence of an AB-like spin system. For weakly coupled systems, the four observed lines correspond to the four different orientations of the A and B nuclei. For a strongly coupled system, two additional lines may appear, the combination lines. The resulting six lines correspond to the four spin orientations, plus the two zero-quantum transitions. It is shown that these six lines are such that there is no net excitation of the AB-like spin system associated with the X transitions. There is no AB coherence created directly by a pulse applied to X. AB coherence is created as the system evolves, and this is responsible for many of the curious effects. This is shown to be true for all spin sub-systems, which are weakly coupled to a strongly coupled sub-system.Key words: NMR, strong coupling, second-order spectra, ABX spin system, combination lines, spectral analysis.

A New Method for Displacement Analysis of Multi-Loop Spatial Linkages Based on Ordered Simple-Opened-Chains

1996 ◽  
Author(s):  
Xian-Wen Kong ◽  
Ting-Li Yang
Keyword(s):  
Continuation Method ◽  
The Other ◽  
New Method ◽  
New Approach ◽  
Strongly Coupled ◽  
Displacement Analysis ◽  
Cpu Time ◽  
Base Points ◽  
Weakly Coupled ◽  
Spatial Linkages

Abstract This paper presents systematically a new method for the displacement analysis (DA) of multi-loop spatial linkages (MLSLs) based on ordered simple-opened-chains (SOCs). In performing DA, a MLSL is converted into not a set of base points, a set of isolated links or a tree with/without isolated links in common use, but a weakly coupled MLSL in this paper. The characteristics of the proposed method are: (a) The number of unknowns in the set of equations for displacement analysis (EDA) of a MLSL is reduced to the minimum; (b) All the possible configurations corresponding to a given set of inputs of a weakly coupled MLSL or a strongly coupled MLSL with the coupled degree k = 1 can be obtained quickly. As compared with the other two methods available to find all the solutions to the DA in the case of MLSL with k = 1, the proposed method is superior to the resultant method in that it is applicable to more complex MLSLs and superior to the continuation method in that it takes much less CPU time to find all the solutions; (c) The set of EDA can be formulated and solved automatically; and (d) The new approach makes it possible to perform the kinematic and kineto-static analyses in a unified and simplified way.

Sign in / Sign up

Export Citation Format

Share Document