THE QUANTUM TRAJECTORY APPROACH TO GEOMETRIC PHASE FOR OPEN SYSTEMS

2005 ◽  
Vol 20 (22) ◽  
pp. 1635-1654 ◽  
Author(s):  
ANGELO CAROLLO
Keyword(s):  
Quantum System ◽  
Open System ◽  
Geometric Phase ◽  
Open Systems ◽  
Quantum Trajectory ◽  
Operational Method ◽  
Markovian Approximation ◽  
Physical Systems ◽  
Quantum Jump ◽  
Trajectory Approach

The quantum jump method for the calculation of geometric phase is reviewed. This is an operational method to associate a geometric phase to the evolution of a quantum system subjected to decoherence in an open system. The method is general and can be applied to many different physical systems, within the Markovian approximation. As examples, two main source of decoherence are considered: dephasing and spontaneous decay. It is shown that the geometric phase is to very large extent insensitive to the former, i.e. it is independent of the number of jumps determined by the dephasing operator.

scholarly journals The quantum trajectory approach to quantum feedback control of an oscillator revisited

2012 ◽  
Vol 370 (1979) ◽  
pp. 5338-5353 ◽  
Author(s):  
Andrew C. Doherty ◽  
A. Szorkovszky ◽  
G. I. Harris ◽  
W. P. Bowen
Keyword(s):  
Master Equation ◽  
Quantum Trajectory ◽  
Measurement Sensitivity ◽  
Position Measurement ◽  
Stochastic Master Equation ◽  
Trajectory Approach ◽  
Quantum Feedback ◽  
Master Equation Approach ◽  
Rotating Wave ◽  
Parametric Driving

We revisit the stochastic master equation approach to feedback cooling of a quantum mechanical oscillator undergoing position measurement. By introducing a rotating wave approximation for the measurement and bath coupling, we can provide a more intuitive analysis of the achievable cooling in various regimes of measurement sensitivity and temperature. We also discuss explicitly the effect of backaction noise on the characteristics of the optimal feedback. The resulting rotating wave master equation has found application in our recent work on squeezing the oscillator motion using parametric driving and may have wider interest.

Non-Markovianity leading to coherence revivals in an open quantum system

2020 ◽  
pp. 2050040
Author(s):  
Y. Yugra ◽  
F. De Zela
Keyword(s):  
Quantum Information ◽  
Quantum System ◽  
Open Quantum System ◽  
Open Systems ◽  
Quantum Correlations ◽  
Experimental Proof ◽  
Optical Setup ◽  
Open Quantum ◽  
All Optical ◽  
Proof Of Principle

Coherence and quantum correlations have been identified as fundamental resources for quantum information tasks. As recently shown, these resources can be interconverted. In multipartite systems, entanglement represents a prominent case among quantum correlations, one which can be activated from coherence. All this makes coherence a key resource for securing the operational advantage of quantum technologies. When dealing with open systems, decoherence hinders full exploitation of quantum resources. Here, we present a protocol that allows reaching the maximal achievable amount of coherence in an open quantum system. By implementing our protocol, or suitable variants of it, coherence losses might be fully compensated, thereby leading to coherence revivals. We provide an experimental proof of principle of our protocol through its implementation with an all-optical setup.

Aspects of the weak-coupling theory of open systems

1983 ◽  
Vol 61 (11) ◽  
pp. 1479-1485 ◽  
Author(s):  
I. D. Cox ◽  
W. E. Hagston ◽  
B. J. Holmes
Keyword(s):  
Perturbation Theory ◽  
Open System ◽  
Weak Coupling ◽  
Open Systems ◽  
Higher Order ◽  
Projection Operators ◽  
Coupling Theory ◽  
Weak Coupling Theory ◽  
Damping Theory ◽  
Insight Into

Damping theory of an open system S is usually formulated in terms of projection operators which introduce nonuniqueness into the analysis. An insight into the nature of the approximations that arise from this aspect of the formalism is revealed by considering systems of varying complexity. This leads to the conclusion that the results of higher order perturbation theory approximations may not be meaningful.

scholarly journals Geometric phase for an adiabatically evolving open quantum system

2004 ◽  
Vol 70 (4) ◽  
Author(s):  
Ingo Kamleitner ◽  
James D. Cresser ◽  
Barry C. Sanders
Keyword(s):  
Quantum System ◽  
Geometric Phase ◽  
Open Quantum System ◽  
Open Quantum

Trapping states and micromaser dynamics by a quantum-trajectory approach

1998 ◽  
Vol 151 (4-6) ◽  
pp. 395-405 ◽  
Author(s):  
F. Casagrande ◽  
M. Garavaglia ◽  
A. Lulli
Keyword(s):  
Quantum Trajectory ◽  
Trajectory Approach

scholarly journals QUANTUM BACKREACTION (CASIMIR) EFFECT WITHOUT INFINITIES: ALGEBRAIC ANALYSIS

2012 ◽  
Vol 14 ◽  
pp. 376-382
Author(s):  
ANDRZEJ HERDEGEN
Keyword(s):  
Hilbert Space ◽  
Quantum Theory ◽  
Quantum System ◽  
Casimir Effect ◽  
Quantum Field ◽  
Expectation Value ◽  
Physical Systems ◽  
Algebra Of Observables ◽  
General Terms ◽  
External Conditions

Casimir effect, in most general terms, is the backreaction of a quantum system responding to an adiabatic change of external conditions. This backreaction is expected to be quantitatively measured by a change in the expectation value of a certain energy observable of the system. However, for this concept to be applicable, the system has to retain its identity in the process. Most prevailing tendencies in the analysis of the effect seem to ignore this question. In general, a quantum theory is defined by an algebra of observables, whose representations by operators in a Hilbert space define concrete physical systems described by the theory. A quantum system retains its identity if both the algebra as well as its representation do not change. We discuss the resulting restrictions for admissible models of changing external conditions. These ideas are applied to quantum field models. No infinities arise, if the algebraic demands are respected.

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