scholarly journals Coherence Trapping in Open Two-Qubit Dynamics

Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2445
Author(s):  
Mariam Algarni ◽  
Kamal Berrada ◽  
Sayed Abdel-Khalek ◽  
Hichem Eleuch
Keyword(s):  
Quantum Coherence ◽  
Open Quantum Systems ◽  
Dynamical Behavior ◽  
Quantum Systems ◽  
Completely Positive Maps ◽  
L1 Norm ◽  
Separable States ◽  
System Parameters ◽  
Quantum Dynamical ◽  
Qubit System

In this manuscript, we examine the dynamical behavior of the coherence in open quantum systems using the l1 norm. We consider a two-qubit system that evolves in the framework of Kossakowski-type quantum dynamical semigroups (KTQDSs) of completely positive maps (CPMs). We find that the quantum coherence can be asymptotically maintained with respect to the values of the system parameters. Moreover, we show that the quantum coherence can resist the effect of the environment and preserve even in the regime of long times. The obtained results also show that the initially separable states can provide a finite value of the coherence during the time evolution. Because of such properties, several states in this type of environments are good candidates for incorporating quantum information and optics (QIO) schemes. Finally, we compare the dynamical behavior of the coherence with the entire quantum correlation.

scholarly journals DYNAMICS OF QUANTUM CORRELATIONS IN TWO-QUBIT SYSTEMS WITHIN NON-MARKOVIAN ENVIRONMENTS

2012 ◽  
Vol 27 (01n03) ◽  
pp. 1345053 ◽  
Author(s):  
ROSARIO LO FRANCO ◽  
BRUNO BELLOMO ◽  
SABRINA MANISCALCO ◽  
GIUSEPPE COMPAGNO
Keyword(s):  
Quantum Discord ◽  
Open Quantum Systems ◽  
Dynamical Behavior ◽  
Quantum Correlations ◽  
Quantum Systems ◽  
Primary Interest ◽  
Common Environment ◽  
Classical Counterpart ◽  
Qubit System ◽  
Dynamics Of Correlations

Knowledge of the dynamical behavior of correlations with no classical counterpart, like entanglement, nonlocal correlations and quantum discord, in open quantum systems is of primary interest because of the possibility to exploit these correlations for quantum information tasks. Here we review some of the most recent results on the dynamics of correlations in bipartite systems embedded in non-Markovian environments that, with their memory effects, influence in a relevant way the system dynamics and appear to be more fundamental than the Markovian ones for practical purposes. Firstly, we review the phenomenon of entanglement revivals in a two-qubit system for both independent environments and a common environment. We then consider the dynamics of quantum discord in non-Markovian dephasing channel and briefly discuss the occurrence of revivals of quantum correlations in classical environments.

scholarly journals Reduced Operator Approximation for Modelling Open Quantum Systems

2015 ◽  
Vol 22 (02) ◽  
pp. 1550008
Author(s):  
A. Werpachowska
Keyword(s):  
Quantum Dynamics ◽  
Quantum Coherence ◽  
Degrees Of Freedom ◽  
Open Quantum Systems ◽  
Interaction Strength ◽  
Quantum Systems ◽  
Computationally Efficient ◽  
Memory Length ◽  
Open Quantum ◽  
Operator Approximation

We present the reduced operator approximation: a simple, physically transparent and computationally efficient method of modelling open quantum systems. It employs the Heisenberg picture of the quantum dynamics, which allows us to focus on the system degrees of freedom in a natural and easy way. We describe different variants of the method, low- and high-order in the system–bath interaction operators, defining them for either general quantum harmonic oscillator baths or specialising them for independent baths with Lorentzian spectral densities. Its wide applicability is demonstrated on the examples of systems coupled to different baths (with varying system–bath interaction strength and bath memory length), and compared with the exact pseudomode and the popular quantum state diffusion approach. The method captures the decoherence of the system interacting with the bath, while conserving the total energy. Our results suggest that quantum coherence effects persist in open quantum systems for much longer times than previously thought.

scholarly journals Quantum Zeno Effect in Open Quantum Systems

2021 ◽  
Author(s):  
Simon Becker ◽  
Nilanjana Datta ◽  
Robert Salzmann
Keyword(s):  
Open Quantum Systems ◽  
Quantum Systems ◽  
Quantum Zeno Effect ◽  
Quantum Dynamical Semigroup ◽  
Open Quantum ◽  
Quantum Operations ◽  
Zeno Effect ◽  
Quantum Dynamical ◽  
Dynamical Semigroup ◽  
First Time

AbstractWe prove the quantum Zeno effect in open quantum systems whose evolution, governed by quantum dynamical semigroups, is repeatedly and frequently interrupted by the action of a quantum operation. For the case of a quantum dynamical semigroup with a bounded generator, our analysis leads to a refinement of existing results and extends them to a larger class of quantum operations. We also prove the existence of a novel strong quantum Zeno limit for quantum operations for which a certain spectral gap assumption, which all previous results relied on, is lifted. The quantum operations are instead required to satisfy a weaker property of strong power-convergence. In addition, we establish, for the first time, the existence of a quantum Zeno limit for open quantum systems in the case of unbounded generators. We also provide a variety of physically interesting examples of quantum operations to which our results apply.

scholarly journals Theory of multiple quantum coherence signals in dilute thermal gases

2021 ◽  
Author(s):  
Benedikt Ames ◽  
Edoardo G Carnio ◽  
Vyacheslav Shatokhin ◽  
Andreas Buchleitner
Keyword(s):  
Quantum Coherence ◽  
Open Quantum Systems ◽  
Laser Pulses ◽  
Quantum Systems ◽  
Multiple Quantum ◽  
Field Coupling ◽  
Dipole Interactions ◽  
Arbitrary Strength ◽  
Characteristic Features ◽  
Multiple Quantum Coherence

Abstract Manifestations of dipole-dipole interactions in dilute thermal gases are difficult to sense because of strong inhomogeneous broadening. Recentexperiments reported signatures of such interactions in fluorescence detection-based measurements of multiple quantum coherence (MQC) signals, with many characteristic features hitherto unexplained. We develop an original open quantum systems theory of MQC in dilute thermal gases, which allows us to resolve this conundrum. Our theory accounts for the vector character of the atomic dipoles as well as for driving laser pulses of arbitrary strength, includes the far-field coupling between the dipoles, which prevails in dilute ensembles, and effectively incorporates atomic motion via a disorder average. We show that collective decay processes -- which were ignored in previous treatments employing the electrostatic form of dipolar interactions -- play a key role in the emergence of MQC signals.

Studying quantum correlations dynamics in the phase space for continuous-variable Werner states and Bell-diagonal states

2019 ◽  
Vol 16 (07) ◽  
pp. 1950109
Author(s):  
Fatima-Zahra Siyouri ◽  
Hicham Ait Mansour ◽  
Fadoua Elbarrichi
Keyword(s):  
Wigner Function ◽  
Quantum Discord ◽  
Open Quantum Systems ◽  
Quantum Correlations ◽  
Continuous Variable ◽  
Quantum Systems ◽  
Qubit System ◽  
Classical Correlations ◽  
Werner States ◽  
System F

We investigate the ability of Wigner function to reveal and measure general quantum correlations in two-qubit open system. For this purpose, we analyze comparatively their dynamics for two different states, continuous-variable Werner states (CWS) and Bell-diagonal states (BDS), independently interacting with dephasing reservoirs. Then, we explore the effects of decreasing the degree of non-Markovianity on their behavior. We show that the presence of both quantum entanglement and quantum discord allow to have a negative Wigner function, in contrast to the result obtained for the closed two-qubit system [F. Siyouri, M. El Baz and Y. Hassouni, The negativity of Wigner function as a measure of quantum correlations, Quantum Inf. Process. 15(10) (2016) 4237–4252]. In fact, we conclude that negativity of Wigner function can be used to capture and quantify the amount of general non-classical correlations in open quantum systems.

scholarly journals Do photosynthetic complexes use quantum coherence to increase their efficiency? Probably not

2021 ◽  
Vol 7 (8) ◽  
pp. eabc4631
Author(s):  
Elinor Zerah Harush ◽  
Yonatan Dubi
Keyword(s):  
Quantum Coherence ◽  
Systems Approach ◽  
Open Quantum Systems ◽  
Structural Parameters ◽  
Quantum Systems ◽  
Direct Evaluation ◽  
Substantial Role ◽  
Physiological Conditions ◽  
Photosynthetic Complexes ◽  
Series Of Experiments

Answering the titular question has become a central motivation in the field of quantum biology, ever since the idea was raised following a series of experiments demonstrating wave-like behavior in photosynthetic complexes. Here, we report a direct evaluation of the effect of quantum coherence on the efficiency of three natural complexes. An open quantum systems approach allows us to simultaneously identify their level of “quantumness” and efficiency, under natural physiological conditions. We show that these systems reside in a mixed quantum-classical regime, characterized by dephasing-assisted transport. Yet, we find that the change in efficiency at this regime is minute at best, implying that the presence of quantum coherence does not play a substantial role in enhancing efficiency. However, in this regime, efficiency is independent of any structural parameters, suggesting that evolution may have driven natural complexes to their parameter regime to “design” their structure for other uses.

Entropy squeezing and coherence for a non-Markovian dissipative qubit system

2019 ◽  
Vol 35 (08) ◽  
pp. 2050046
Author(s):  
K. Berrada
Keyword(s):  
Quantum Coherence ◽  
Photonic Band Gap ◽  
Dynamical Behavior ◽  
Partial Coherence ◽  
Model Parameters ◽  
Entropy Squeezing ◽  
Qubit System ◽  
The Impact ◽  
Photonic Band ◽  
Gap Width

We examine the impact of the non-Markovian environment on the dynamical behavior of the quantum coherence and entropy squeezing considering a two-level atomic system (qubit) immersed in a reservoir with zero-temperature for two types of non-Markovian environments. We consider a cavity little off-resonance with the transition frequency of the qubit and the case of a non-perfect photonic band gap (PBG). We show that the amount of coherence is dependent on the structure of the environment and influenced through the memory effects. We obtain that the delay and revival of the coherence loss might take place by controlling the detuning of the cavity-qubit system. Whereas, a partial coherence trapping occurs in non-ideal PBG and the decrease of the gap width will destroy the coherence. On the other hand, we show the situation for which the squeezing is occurring and enhanced with respect to the main parameters for the system. Finally, we display the monotonic dependence of the quantum coherence and squeezing on the main model parameters.

Survival of quantum coherence in Born-Markov Open Quantum Systems

2017 ◽  
Author(s):  
Armando Perez-Leija ◽  
Diego Guzman-Silva ◽  
Roberto de J. Leon-Montiel ◽  
Markus Gräfe ◽  
Kurt Busch ◽  
...  
Keyword(s):  
Quantum Coherence ◽  
Open Quantum Systems ◽  
Quantum Systems ◽  
Open Quantum
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