Time evolution of the coarse-graining-smoothed Wigner operator in an amplitude dissipative channel: from a pure state to a mixed state

2014 ◽  
Vol 89 (6) ◽  
pp. 065101 ◽  
Author(s):  
Rui He ◽  
Hong-yi Fan
Keyword(s):  
Time Evolution ◽  
Mixed State ◽  
Pure State ◽  
Coarse Graining ◽  
Wigner Operator

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.

Probabilistic secret sharing through noise quantum channe

2012 ◽  
Vol 12 (3&4) ◽  
pp. 253-261
Author(s):  
Satyabrata Adhikari ◽  
Indranil Chakrabarty ◽  
Pankaj Agrawal
Keyword(s):  
Quantum Information ◽  
Secret Sharing ◽  
Mixed State ◽  
Pure State ◽  
Noisy Channel ◽  
Noisy Channels ◽  
Superdense Coding ◽  
Classical Information ◽  
Phase Damping ◽  
Realistic Situation

In a realistic situation, the secret sharing of classical or quantum information will involve the transmission of this information through noisy channels. We consider a three qubit pure state. This state becomes a mixed-state when the qubits are distributed over noisy channels. We focus on a specific noisy channel, the phase-damping channel. We propose a protocol for secret sharing of classical information with this and related noisy channels. This protocol can also be thought of as cooperative superdense coding. We also discuss other noisy channels to examine the possibility of secret sharing of classical information.

MIXED-STATE ENTANGLEMENT IN THE LIGHT OF PURE-STATE ENTANGLEMENT CONSTRAINED BY SUPERSELECTION RULES

2005 ◽  
Author(s):  
STEPHEN D. BARTLETT ◽  
HOWARD. M. WISEMAN ◽  
ROBERT W. SPEKKENS ◽  
ANDREW C. DOHERTY
Keyword(s):  
Mixed State ◽  
Pure State

TIME EVOLUTION OF MEISSNER EFFECT IN EuBa2Cu3O7−δ

1990 ◽  
Vol 04 (02) ◽  
pp. 129-135 ◽  
Author(s):  
A. S. SHERBAKOV ◽  
V. E. STARTSEV ◽  
E. G. VALIULIN ◽  
V. L. KOZHEVNIKOV
Keyword(s):  
Magnetic Fields ◽  
Time Evolution ◽  
Mixed State ◽  
Differential Susceptibility ◽  
Meissner Effect ◽  
Flux Trapping ◽  
Sign Inversion ◽  
External Conditions

The results of temperature and time (at T = 4.2 K ) dependent magnetization (M) measurements on polycrystalline high T c superconductor EuBa 2 Cu 3O7−δ are reported for different magnetic fields from 2.2 kOe to 35 kOe. The measurements were performed in the field-cooled regime (measuring the Meissner effect). A new phenomenon is found: the magnetization sign inversion from negative to positive during the time at which the external conditions (T, H) remains unchanged. The differential susceptibility in a new mixed state with M > 0 is diamagnetic. It is shown that origin of this state is not connected with a flux trapping, but rather caused by the unusual nature of the vortex themselves in FC mixed state of high T c superconductors.

scholarly journals On the Emergence of the Microcanonical Description from a Pure State

2003 ◽  
Vol 18 (17) ◽  
pp. 2947-2993 ◽  
Author(s):  
N. D. Hari Dass ◽  
S. Kalyana Rama ◽  
B. Sathiapalan
Keyword(s):  
Pure State ◽  
Degrees Of Freedom ◽  
Coarse Graining ◽  
Resonant Absorption ◽  
Decay Rates ◽  
Quantum Mechanical ◽  
Classical Statistical Mechanics ◽  
General Terms ◽  
Black Hole Information ◽  
Usual Formalism

We study, in general terms, the process by which a pure state can "self-thermalize" and appear to be described by a microcanonical density matrix. This requires a quantum mechanical version of the Gibbsian coarse graining that conceptually underlies classical statistical mechanics. We make use of some extra degrees of freedom that are necessary for this. Interaction between these degrees and the system can be understood as a process of resonant absorption and emission of "soft quanta." This intuitive picture allows one to state a criterion for when self thermalization occurs. This paradigm also provides a method for calculating the thermalization rate using the usual formalism of atomic physics for calculating decay rates. We contrast our prescription for coarse graining, which is somewhat dynamical, with the earlier approaches that are intrinsically kinematical. An important motivation for this study is the black hole information paradox.

scholarly journals THE EXACT RENORMALIZATION GROUP IN ASTROPHYSICS

2001 ◽  
Vol 16 (11) ◽  
pp. 2041-2046 ◽  
Author(s):  
JOSÉ GAITE
Keyword(s):  
Renormalization Group ◽  
Probability Distribution ◽  
Time Evolution ◽  
Planck Equation ◽  
Coarse Graining ◽  
Renormalization Group Equation ◽  
Group Equation ◽  
Change Of Scale ◽  
Exact Renormalization Group ◽  
Fokker Planck

The coarse-graining operation in hydrodynamics is equivalent to a change of scale which can be formalized as a renormalization group transformation. In particular, its application to the probability distribution of a self-gravitating fluid yields an "exact renormalization group equation" of Fokker-Planck type. Since the time evolution of that distribution can also be described by a Fokker-Planck equation, we propose a connection between both equations, that is, a connection between scale and time evolution. We finally remark on the essentially non-perturbative nature of astrophysical problems, which suggests that the exact renormalization group is the adequate tool for them.

Quantum Dynamics and Entropy in a Single-Cooper-Pair Box with a Single-Mode Cavity Field

2003 ◽  
Vol 17 (14) ◽  
pp. 2699-2713 ◽  
Author(s):  
Meng Zhang ◽  
Jian Zou ◽  
Bin Shao
Keyword(s):  
Mixed State ◽  
Pure State ◽  
Quantum Dynamics ◽  
Cooper Pair ◽  
Single Mode ◽  
Quantum Entropy ◽  
Cavity Field ◽  
Cooper Pair Box ◽  
Quantized Field ◽  
Single Mode Cavity

We consider a single-Cooper-pair box biased by a classical voltage and also irradiated by a single-mode quantized field. We assume that the box is initially in a mixed state, and investigate the quantum dynamics of the Cooper-pair box and show that the collapse and revival phenomenon can exist in this system. We also study the quantum entropy of the single-Cooper-pair box and discuss the effects of the different parameters on this quantum entropy. We find that the box, which is initially in a mixed state, may evolve into an almost pure state.

scholarly journals SOME FEATURES OF THE STATE-SPACE TRAJECTORIES FOLLOWED BY ROBUST ENTANGLED FOUR-QUBIT STATES DURING DECOHERENCE

2010 ◽  
Vol 08 (03) ◽  
pp. 505-515 ◽  
Author(s):  
A. P. MAJTEY ◽  
A. BORRAS ◽  
A. R. PLASTINO ◽  
M. CASAS ◽  
A. PLASTINO
Keyword(s):  
State Space ◽  
Recent Work ◽  
Mixed State ◽  
Pure State ◽  
The State ◽  
Time Dependent ◽  
Space Trajectories ◽  
Geometrical Features ◽  
Initial States ◽  
Qubit States

In a recent work (Borras et al., Phys. Rev. A79 (2009) 022108), we have determined, for various decoherence channels, four-qubit initial states exhibiting the most robust possible entanglement. Here, we explore some geometrical features of the trajectories in state space generated by the decoherence process, connecting the initially robust pure state with the completely decohered mixed state obtained at the end of the evolution. We characterize these trajectories by recourse to the distance between the concomitant time-dependent mixed state and different reference states.

COARSE-GRAINING INVARIANT ORBITS OF ONE-DIMENSIONAL ℤp-LINEAR CELLULAR AUTOMATA

1996 ◽  
Vol 06 (12a) ◽  
pp. 2237-2297 ◽  
Author(s):  
ANDRÉ M. BARBÉ
Keyword(s):  
Cellular Automata ◽  
Periodic Solutions ◽  
Time Evolution ◽  
Coarse Graining ◽  
One Dimensional ◽  
State Time ◽  
All Solutions ◽  
Invariance Problem ◽  
Self Similar ◽  
Existence Of Periodic Solutions

This paper studies the properties of state-time evolution patterns of one-dimensional linear cellular automata over the field ℤp (p prime) which are invariant under certain coarse-graining operations. A procedure is developed for finding all solutions to this invariance problem. The resulting patterns display a complexity which may range from periodic over self-similar, quasi-periodic, quasi-randomlike towards randomlike. Conditions for the existence of periodic solutions are derived.

scholarly journals Impossibility of Distinguishing Two Preparations for a Pure State from No-signaling

Quanta ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 16-21
Author(s):  
Arun K. Pati
Keyword(s):  
Quantum Theory ◽  
Infinite Number ◽  
Mixed State ◽  
Physical System ◽  
Pure State ◽  
Entangled State ◽  
No Signaling

A pure state of a physical system can be prepared in an infinite number of ways. Quantum theory dictates that given a pure state of a physical system it is impossible to distinguish two preparation procedures. Here, we show that the impossibility of distinguishing two preparation procedures for the same pure state follows from the no-signaling principle. Extending this result for a pure bipartite entangled state entails that the impossibility of distinguishing two preparation procedures for a mixed state follows from the impossibility of distinguishing two preparations for a pure bipartite state.Quanta 2020; 9: 16–21.

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