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Entropy Change in Reversible Processes

Entropy Change in Reversible Processes

In the Carnot engine, which achieves the maximum efficiency between two reservoirs of fixed temperatures, the total change in entropy is zero. The observation can be generalized by considering any reversible cyclic process consisting of many Carnot cycles. Thus, it can be stated that the total entropy change of any ideal reversible cycle is zero.
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.

Entropy and the Second Law of Thermodynamics

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The second law of thermodynamics can be stated quantitatively using the concept of entropy. Entropy is the measure of disorder of the system.
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Standard Entropy Change for a Reaction

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Entropy is a state function, so the standard entropy change for a chemical reaction (ΔS°rxn) can be calculated from the difference in standard entropy between the products and the reactants.

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Agonism and Antagonism: Quantification

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A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

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Published on: September 5, 2019

A new entropic quantum correlation measure for adversarial systems.

Biveen Shajilal^1,2, Elanor Huntington³, Ping Koy Lam^4,5,6

¹Centre for Quantum Computation and Communication Technology, Research School of Engineering, The Australian National University, Canberra, ACT, 2601, Australia. biveen.shajilal@anu.edu.au.

Scientific Reports

|January 25, 2023

Summary

Researchers introduced entropic accord, a new measure of quantum correlations. This quantity fits between entanglement and discord, offering a distinct perspective on non-classical correlations in quantum systems.

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Area of Science:

Quantum Information Theory
Quantum Mechanics
Quantum Statistics

Background:

Quantum correlations exceed classical statistical frameworks.
Quantum entanglement is a key quantum correlation, vital for quantum information.
Non-entangled states can exhibit quantum correlations beyond classical descriptions, quantified by discord.

Purpose of the Study:

Introduce a novel measure of quantum correlations named entropic accord.
Establish entropic accord as a distinct quantifier of non-classical correlations.
Investigate the relationship between entanglement, entropic accord, and discord.

Main Methods:

Defined entropic accord via optimized minimax mutual information of projective measurement outcomes.
Analyzed two-qubit states to explore quantum correlation measures.
Established a strict hierarchy among entanglement, entropic accord, and discord.

Main Results:

Demonstrated a strict hierarchy: entanglement < entropic accord < discord for two-qubit states.
Identified a class of quantum correlations distinct from both entanglement and discord.
Entropic accord provides a potentially more intuitive measure in specific contexts.

Conclusions:

Entropic accord offers a new, nuanced understanding of quantum correlations.
The established hierarchy clarifies the landscape of quantum correlations beyond entanglement.
This measure enhances the toolkit for analyzing quantum correlations in quantum information processing.