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Related Concept Videos

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...
Open and closed-loop control systems01:17

Open and closed-loop control systems

Control systems are foundational elements in automation and engineering. They are broadly categorized into open-loop and closed-loop systems. These classifications hinge on the presence or absence of feedback mechanisms, significantly influencing the system's performance, complexity, and application.
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Conservation of Energy in Control Volume01:14

Conservation of Energy in Control Volume

Consider a turbine operating under steady-flow conditions. The control volume is drawn around the turbine, with fluid entering at one point and exiting at another. The turbine extracts energy from the fluid, which performs mechanical work (shaft work).
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Entropy and the Second Law of Thermodynamics01:20

Entropy and the Second Law of Thermodynamics

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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Entropy and the Second Law of Thermodynamics01:26

Entropy and the Second Law of Thermodynamics

Consider an isolated system in which a hot object is placed in contact with a cold one. This is an irreversible process that eventually leads both objects to reach the same equilibrium temperature. It is crucial to note that the constituents of any substance exhibit increased disorder at higher temperatures. As a cold substance absorbs heat, its constituents become more disordered. The energy transfer from a hotter object to a cooler one increases the system's disorder or randomness. This...

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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

Quantum conditions on dynamics and control in open systems.

Lian-Ao Wu1, Arjun Bharioke, Paul Brumer

  • 1Center for Quantum Information and Quantum Control, and Chemical Physics Theory Group, Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.

The Journal of Chemical Physics
|August 7, 2008
PubMed
Summary

Quantum mechanics allows controlling system dynamics. If a system

Area of Science:

  • Quantum mechanics
  • Quantum dynamics
  • Quantum information theory

Background:

  • Controlling quantum system dynamics is crucial for quantum technologies.
  • Understanding system-environment interactions is key to predicting evolution.
  • Previous studies focused on specific system-environment models.

Purpose of the Study:

  • To derive general quantum conditions for controlling system dynamics.
  • To establish criteria for avoiding unwanted state evolution.
  • To explore implications for quantum information processing and spectroscopy.

Main Methods:

  • Derivation of quantum conditions based on system and environment coupling.
  • Analysis of state evolution using Kraus operators.
  • Mathematical formulation of conditions for state subspace avoidance.

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An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
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An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

Published on: December 4, 2017

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Last Updated: Jul 3, 2026

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

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
11:03

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

Published on: December 4, 2017

Main Results:

  • A general condition M(0) > dM(2) is derived for avoiding a target subspace H(2).
  • The number of Kraus operators (d) can be significantly smaller than the bath dimension.
  • If the condition is not met, avoiding H(2) requires stringent physical constraints.

Conclusions:

  • General quantum conditions for controlling system dynamics are established.
  • The findings provide a framework for designing quantum systems with desired evolutions.
  • The results have potential applications in areas like molecular energy transfer.