Explicit Kraus operator-sum representations for time-evolution of Fermi systems in amplitude- and phase-decay processes

2015 ◽  
Vol 93 (11) ◽  
pp. 1356-1359
Author(s):  
Xian-Feng Chen ◽  
Li-Li Hou
Keyword(s):  
Time Evolution ◽  
Atomic System ◽  
Decay Process ◽  
Entangled State ◽  
Fermi Systems ◽  
Kraus Operator ◽  
Evolution Law ◽  
Quantum Jump ◽  
Fermi Operator ◽  
Set Up

We set up the fermionic thermal entangled state approach to address Fermi operator master equations for the amplitude- and phase-decay processes and find the explicit Kraus operator-sum representations (KOSR) describing time-evolution of Fermi systems. As an application of KOSR, the evolution law of the two-level atomic system interacting with a photon field in these two decay processes is analytically derived, which shows that the interaction system has a quantum jump as a result of dissipation, but it always remains unchanged in the phase-decay process.

Quantum discord and entanglement of two atoms in a micromaser-type system

2016 ◽  
Vol 30 (15) ◽  
pp. 1650190
Author(s):  
Xue-Qun Yan ◽  
Fu-Zhong Wang
Keyword(s):  
Time Evolution ◽  
Mixed State ◽  
Quantum Discord ◽  
Type System ◽  
Complete Loss ◽  
Entangled State ◽  
Fock State

The correlations dynamics of two atoms in the case of a micromaser-type system is investigated. We show that the entangled state can be created by initially maximally mixed state and there exist collapse and revival phenomena for the time evolutions of both entanglement and quantum discord under the system considered as the field is initially in the Fock state. Our results confirm that entanglement and quantum discord have similar behaviors in certain time ranges, such as their oscillations during the time evolution being almost in phase, but they also present significant differences, such as quantum discord being maintained even after the complete loss of entanglement. Furthermore, we exhibit clearly that the dynamics of quantum discord under the action of environment are intimately related to the generation and evolution of entanglement.

New approach for obtaining the time-evolution law of a chaotic light field in a damping—gaining process

2012 ◽  
Vol 21 (8) ◽  
pp. 080302 ◽  
Author(s):  
Li-Hua Gong ◽  
Nan-Run Zhou ◽  
Li-Yun Hu ◽  
Hong-Yi Fan
Keyword(s):  
Time Evolution ◽  
Light Field ◽  
New Approach ◽  
Evolution Law

ANALYSIS OF THE LASER PROCESS WITH THREE DIFFERENT INITIAL STATES

2014 ◽  
Vol 28 (08) ◽  
pp. 1450029 ◽  
Author(s):  
FUYI YOU ◽  
JUNHUA CHEN ◽  
HONGYI FAN
Keyword(s):  
Photon Number ◽  
Entangled State ◽  
State Representation ◽  
Evolution Law ◽  
Laser Process ◽  
Specific Entropy ◽  
Degree Of Coherence ◽  
The Common ◽  
The Mean ◽  
Initial States

We analyze the laser process with three different initial states using the entangled state representation, obtain the evolution law of the mean photon number, the entropy, the specific entropy, the second degree of coherence and the Wigner functions, and find out the common characteristics of these three processes.

scholarly journals Past of a particle in an entangled state

2017 ◽  
Vol 15 (08) ◽  
pp. 1740019 ◽  
Author(s):  
Dilip Paneru ◽  
Eliahu Cohen
Keyword(s):  
Time Evolution ◽  
Single Particle ◽  
Quantum Particle ◽  
Higher Order ◽  
Entangled State ◽  
Entire System ◽  
Single Quantum ◽  
Single Particles ◽  
Top Down ◽  
The Past

Vaidman has proposed a controversial criterion for determining the past of a single quantum particle based on the “weak trace” it leaves. We here consider more general examples of entangled systems and analyze the past of single, as well as pairs of entangled pre- and postselected particles. Systems with nontrivial time evolution are also analyzed. We argue that in these cases, examining only the single-particle weak trace provides information which is insufficient for understanding the system as a whole. We therefore suggest to examine, alongside with the past of single particles, also the past of pairs, triplets and eventually the entire system, including higher-order, multipartite traces in the analysis. This resonates with a recently proposed top-down approach by Aharonov, Cohen and Tollaksen for understanding the structure of correlations in pre- and postselected systems.

scholarly journals NEUTRINO OSCILLATIONS, ENTANGLEMENT AND COHERENCE: A QUANTUM FIELD THEORY STUDY IN REAL TIME

2011 ◽  
Vol 26 (32) ◽  
pp. 5261-5297 ◽  
Author(s):  
JUN WU ◽  
JIMMY A. HUTASOIT ◽  
DANIEL BOYANOVSKY ◽  
RICHARD HOLMAN
Keyword(s):  
Real Time ◽  
Time Evolution ◽  
Finite Time ◽  
Charged Lepton ◽  
Oscillatory Behavior ◽  
Entangled State ◽  
Neutrino Mixing ◽  
Detection Rates ◽  
Long Baseline ◽  
S Matrix

The dynamics of neutrino mixing and oscillations are studied directly in finite real time in a model that effectively describes charged current weak interactions. Finite time corrections to the S-matrix result for the appearance and disappearance probabilities are obtained. It is observed that these effects may be of the same order of the S-matrix result in long-baseline appearance experiments. We argue that fundamentally, the S-matrix is ill-suited to describe long-baseline events due to the fact that the neutrino is produced in an entangled state with the charged lepton, which can be disentangled by the measurement of the charged lepton near the production site. The appearance and disappearance far-detection process is described from the time evolution of this disentangled "collapsed" state, allowing us to establish the conditions under which factorization of detection rates emerges in long-baseline experiments. We also study the time evolution of the reduced density matrix and show explicitly how oscillations are manifest in the off-diagonal terms, i.e. coherences, as a result of a finite time analysis. Lastly, we study a model for the "GSI anomaly" by obtaining the time evolution of the population of parent and daughter particles directly in real time. We confirm that the decay rate of parent and growth rate of daughters do not feature oscillatory behavior from interference of mass eigenstates.

Time evolution law of the Laguerre-polynomial-weighted chaotic photon field in an amplitude-damping channel

2015 ◽  
Vol 93 (3) ◽  
pp. 283-289 ◽  
Author(s):  
Cheng Da ◽  
Qian-Fan Chen ◽  
Peng-Fei Zhang ◽  
Hong-Yi Fan
Keyword(s):  
Decay Rate ◽  
Time Evolution ◽  
Generating Function ◽  
Density Operator ◽  
Laguerre Polynomial ◽  
Hermite Polynomials ◽  
Evolution Law ◽  
Amplitude Damping ◽  
Photon Field ◽  
Amplitude Damping Channel

We examine how a Laguerre-polynomial-weighted chaotic photon field (LPWCPF), whose density operator is [Formula: see text], evolves in an amplitude-damping channel. By using a newly derived generating function of two-variable Hermite polynomials we obtain the evolution law of LPWCPF, which turns out to be a new LPWCPF with a new parameter, depending on 1 − e−2κt, where κ represents decay rate. The technique of integration (summation) within an ordered product of operators is used in our discussions.

scholarly journals Density-operator evolution: Complete positivity and the Keldysh real-time expansion

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Viktor Reimer ◽  
Maarten Wegewijs
Keyword(s):  
Real Time ◽  
Time Evolution ◽  
Density Operator ◽  
Solvable Model ◽  
Complete Positivity ◽  
Memory Kernel ◽  
Kraus Operator ◽  
Statistical Field ◽  
Kernel Operators ◽  
Kraus Operators

We study the reduced time-evolution of general open quantum systems by combining insights from quantum-information and statistical field theory. Inspired by prior work [Eur. Phys. Lett.~102, 60001 (2013) and Phys. Rev. Lett.~111, 050402 (2013)] we establish the explicit structure guaranteeing the complete positivity (CP) and trace-preservation (TP) of the real-time evolution expansion in terms of the microscopic system-environment coupling.This reveals a fundamental two-stage structure of the coupling expansion: Whereas the first stage naturally defines the dissipative timescales of the system -before having integrated out the environment completely- the second stage sums up elementary physical processes, each described by a CP superoperator. This allows us to establish the highly nontrivial functional relation between the (Nakajima-Zwanzig) memory-kernel superoperator for the reduced density operator and novel memory-kernel operators that generate the Kraus operators of an operator-sum. We illustrate the physically different roles of the two emerging coupling-expansion parameters for a simple solvable model. Importantly, this operational approach can be implemented in the existing Keldysh real-time technique and allows approximations for general time-nonlocal quantum master equations to be systematically compared and developed while keeping the CP and TP structure explicit.Our considerations build on the result that a Kraus operator for a physical measurement process on the environment can be obtained by `cutting' a group of Keldysh real-time diagrams `in half'. This naturally leads to Kraus operators lifted to the system plus environment which have a diagrammatic expansion in terms of time-nonlocal memory-kernel operators. These lifted Kraus operators obey coupled time-evolution equations which constitute an unraveling of the original Schroedinger equation for system plus environment. Whereas both equations lead to the same reduced dynamics, only the former explicitly encodes the operator-sum structure of the coupling expansion.

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