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.

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 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.

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 “What Is Life?”: Open Quantum Systems Approach

2021 ◽  
Author(s):  
Andrei Khrennikov ◽  
Irina Basieva
Keyword(s):  
Steady State ◽  
Quantum Dynamics ◽  
Systems Approach ◽  
Open Quantum Systems ◽  
Quantitative Measure ◽  
Second Law Of Thermodynamics ◽  
Quantum Systems ◽  
Order Structure ◽  
Initial State ◽  
Open Quantum

Abstract Recently the quantum formalism and methodology started to be applied to modeling of information processing in biosystems, mainly to the process of decision making and psychological behavior (but some applications to microbiology and genetics are considered as well). Since a living system is fundamentally open (an isolated biosystem is dead), the theory of open quantum systems is the most powerful tool for life-modeling. In this paper, we turn to the famous Schrödinger book “What is life?” and reformulate his speculations in terms of this theory. Schrödinger pointed toorder preservation as one of the main distinguishing features of biosystems. Entropy is the basic quantitative measure of order. In physical systems, entropy has the tendency to increase (Second Law of Thermodynamics for isolated classical systems and dissipation in open classical and quantum systems). Schrödinger emphasized the ability of biosystems to beat this tendency. We demonstrate that systems processing information in the quantum-like way can preservethe order-structure expressed by the quantum (von Neumann or linear) entropy. We emphasize the role of the special class of quantum dynamics and initial states generating the camel-like graphs for entropy-evolution in the process of interaction with a new environment ℰ: 1) entropy (disorder) increasing in the process of adaptation to the specific features of ℰ; 2) entropy decreasing (order increasing) resulting from adaptation; 3) the restoration of order or even its increase for limiting steady state. In the latter case the steady state entropy can be even lower than the entropy of the initial state.

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

scholarly journals Open-quantum-systems approach to complementarity in neutral-kaon interferometry

2016 ◽  
Vol 94 (6) ◽  
Author(s):  
Gustavo de Souza ◽  
J. G. G. de Oliveira ◽  
Adalberto D. Varizi ◽  
Edson C. Nogueira ◽  
Marcos D. Sampaio
Keyword(s):  
Systems Approach ◽  
Open Quantum Systems ◽  
Neutral Kaon ◽  
Quantum Systems ◽  
Open Quantum ◽  
Kaon Interferometry

Dynamics of coherence under Markovian and non-Markovian environments

2017 ◽  
Vol 31 (35) ◽  
pp. 1750329 ◽  
Author(s):  
Zhong-Xiao Wang ◽  
Teng Ma ◽  
Shu-Hao Wang ◽  
Tie-Jun Wang ◽  
Chuan Wang
Keyword(s):  
Density Matrix ◽  
Upper Bound ◽  
Quantum Coherence ◽  
Quantum Discord ◽  
Open Quantum Systems ◽  
Quantum Systems ◽  
Initial State ◽  
Single Qubit ◽  
Markovian Processes ◽  
Markovian Dynamics

The behavior of quantum coherence is studied under Markovian and non-Markovian dynamics for open quantum systems. For single qubit systems, we show that the coherence depending on the off-diagonal elements of the density matrix is the upper bound of the coherence depending on the relative entropy under both Markovian and non-Markovian processes. For two-qubit systems, in both Markovian and non-Markovian processes, quantum discord and coherence show less sensitivity to the initial state than quantum entanglement. We also find that the quantum discord has similar behaviors with coherence under both Markovian and non-Markovian dynamics.

scholarly journals Open quantum systems approach to atomtronics

2010 ◽  
Vol 82 (1) ◽  
Author(s):  
R. A. Pepino ◽  
J. Cooper ◽  
D. Meiser ◽  
D. Z. Anderson ◽  
M. J. Holland
Keyword(s):  
Systems Approach ◽  
Open Quantum Systems ◽  
Quantum Systems ◽  
Open Quantum
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