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Related Concept Videos

Woodward–Hoffmann Selection Rules and Microscopic Reversibility01:34

Woodward–Hoffmann Selection Rules and Microscopic Reversibility

Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
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Multimachine stability analysis is crucial for understanding the dynamics and stability of power systems with multiple synchronous machines. The objective is to solve the swing equations for a network of M machines connected to an N-bus power system.
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Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

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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.
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Reversible and Irreversible Processes01:14

Reversible and Irreversible Processes

The thermodynamic processes can be classified into reversible and irreversible processes. The processes that can be restored to their initial state are called reversible processes. It is only possible if the process is in quasi-static equilibrium, i.e., it takes place in infinitesimally small steps, and the system remains at equilibrium However, these are ideal processes and do not occur naturally. An ideal system undergoing a reversible process is always in thermodynamic equilibrium within...
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Related Experiment Video

Updated: Jul 2, 2026

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
06:24

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51

Published on: February 13, 2019

Multistage entanglement swapping.

Alexander M Goebel1, Claudia Wagenknecht, Qiang Zhang

  • 1Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany.

Physical Review Letters
|September 4, 2008
PubMed
Summary
This summary is machine-generated.

Researchers experimentally demonstrated entanglement swapping over two stages, distributing entanglement between independent photons. This achievement is a crucial step toward building quantum repeaters for advanced quantum networks.

Related Experiment Videos

Last Updated: Jul 2, 2026

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
06:24

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51

Published on: February 13, 2019

Area of Science:

  • Quantum Information Science
  • Experimental Quantum Physics
  • Quantum Communication

Background:

  • Entanglement swapping enables the distribution of entanglement between particles that have never interacted.
  • Cascaded entanglement swapping is essential for developing quantum repeaters and long-distance quantum communication.

Purpose of the Study:

  • To experimentally demonstrate entanglement swapping over two sequential quantum stages.
  • To generate and distribute entanglement between photons from independent sources using cascaded processes.

Main Methods:

  • Utilized three pairs of polarization-entangled photons.
  • Performed two sequential Bell-state measurements.
  • Characterized the resulting entanglement using an entanglement witness.

Main Results:

  • Successfully demonstrated entanglement swapping over two cascaded stages.
  • Generated entanglement between two photons that did not share a common past.
  • Confirmed the entangled state of the final two photons.

Conclusions:

  • The experiment successfully showed the feasibility of multi-stage entanglement swapping.
  • This work is a significant advancement towards the realization of a functional quantum repeater.
  • Highlights the potential of cascaded entanglement swapping for quantum networking.