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Related Concept Videos

Entropy Change in Reversible Processes01:10

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 Changes Accompanying Specific Processes01:21

Entropy Changes Accompanying Specific Processes

Entropy, a measure of disorder in a system, changes during phase transitions like freezing or boiling. At the transition temperature Ttrs, where two phases are in equilibrium, the phase transition is a reversible process. The entropy change can be calculated from a substance's enthalpy of transition using the equation ΔStrs = ΔtrsH /Ttrs.When a perfect gas expands isothermally from one volume to another, entropy increases logarithmically with volume. Conversely, isothermal compression results...
Second Law of Thermodynamics02:49

Second Law of Thermodynamics

In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Processes that involve an increase in entropy of the system (ΔS > 0) are very often spontaneous; however, examples to the contrary are plentiful. By expanding consideration of entropy changes to include the surroundings, a significant conclusion regarding the relation between this property and spontaneity may be reached. In thermodynamic models, the...
Second Law of Thermodynamics00:53

Second Law of Thermodynamics

The Second Law of Thermodynamics states that entropy, or the amount of disorder in a system, increases each time energy is transferred or transformed. Each energy transfer results in a certain amount of energy that is lost—usually in the form of heat—that increases the disorder of the surroundings. This can also be demonstrated in a classic food web. Herbivores harvest chemical energy from plants and release heat and carbon dioxide into the environment. Carnivores harvest the chemical energy...
The Entropy as a State Function01:14

The Entropy as a State Function

Consider an arbitrary process that moves between two specific states (A and B) in a cyclic manner. This process is reversible and broken down into smaller parts that each follow a Carnot cycle. A Carnot cycle has two isothermal (constant temperature) processes. During these processes, the ratio of the amount of heat transferred to their respective temperature remains constant. The other two processes in the Carnot cycle are also reversible but adiabatic, which means they occur without any heat...
¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...

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Related Experiment Video

Updated: Jun 12, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
07:56

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

Published on: September 5, 2019

Characterizing the nonlocal correlations created via entanglement swapping.

C Branciard1, N Gisin, S Pironio

  • 1Group of Applied Physics, University of Geneva, 20 rue de l'Ecole-de-Médecine, CH-1211 Geneva 4, Switzerland.

Physical Review Letters
|May 21, 2010
PubMed
Summary

Entanglement swapping creates nonlocal correlations between quantum systems. New local models reveal that such systems violate Bell inequalities even at 50% visibility, strengthening nonlocality tests.

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Generation and Coherent Control of Pulsed Quantum Frequency Combs
06:42

Generation and Coherent Control of Pulsed Quantum Frequency Combs

Published on: June 8, 2018

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Last Updated: Jun 12, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
07:56

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

Published on: September 5, 2019

Generation and Coherent Control of Pulsed Quantum Frequency Combs
06:42

Generation and Coherent Control of Pulsed Quantum Frequency Combs

Published on: June 8, 2018

Area of Science:

  • Quantum Information Science
  • Foundations of Quantum Mechanics

Background:

  • Quantum entanglement allows distant systems to exhibit correlations.
  • Entanglement swapping enables entanglement between systems that never interacted.
  • Characterizing nonlocality in swapped entangled states is crucial for quantum information processing.

Purpose of the Study:

  • To introduce novel local models for characterizing nonlocality in entanglement swapping.
  • To develop stronger tests for quantum nonlocality using these models.
  • To determine the minimum visibility threshold for Bell inequality violation in swapped entangled states.

Main Methods:

  • Development of local models with uncorrelated local variables for initially uncorrelated quantum systems.
  • Application of these models to analyze states generated via entanglement swapping.
  • Derivation of Bell-type inequalities tailored to the assumptions of the local models.

Main Results:

  • The introduced local models provide a stricter framework for testing nonlocality.
  • Entangled pairs generated through entanglement swapping violate Bell-type inequalities.
  • Violation is demonstrated to occur for visibilities as low as 50% under the model's assumptions.

Conclusions:

  • The study presents a new theoretical framework for understanding nonlocality in entanglement swapping.
  • The findings indicate that nonlocality is robust in swapped entangled states, detectable even at moderate visibilities.
  • This work has implications for the fundamental understanding of quantum correlations and the development of quantum technologies.