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Related Concept Videos

Effects of feedback01:24

Effects of feedback

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Feedback in control systems plays a critical role in shaping various operational parameters, extending beyond simple error reduction to influence stability, bandwidth, gain, impedance, and sensitivity. Understanding these effects requires examining a basic feedback system characterized by defined input, output, error, and feedback signals.
Feedback significantly modifies the gain of a control system. The gain of a system without feedback is altered by a factor of one plus GH, where G represents...
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Feedback control systems01:26

Feedback control systems

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Feedback control systems are categorized in various ways based on their design, analysis, and signal types.
Linear feedback systems are theoretical models that simplify analysis and design. These systems operate under the principle that their output is directly proportional to their input within certain ranges. For instance, an amplifier in a control system behaves linearly as long as the input signal remains within a specific range. However, most physical systems exhibit inherent nonlinearity...
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Root Loci for Positive-Feedback Systems01:23

Root Loci for Positive-Feedback Systems

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The Hartley oscillator is a positive feedback system that sustains oscillations by feeding the output back to the input in phase, thereby reinforcing the signal. Positive feedback systems can be viewed as negative feedback systems with inverted feedback signals. In these systems, the root locus encompasses all points on the s-plane where the angle of the system transfer function equals 360 degrees.
The construction rules for the root locus in positive feedback systems are similar to those in...
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Feedback Loops01:01

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In most cases, excessive hormone production is prevented by negative feedback—a loop that starts with a stimulus inducing the release of a particular substance, like a hormone, to maintain a certain level before triggering a signal that results in a decrease in further release of the hormone.
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Allosteric Regulation

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Allosteric regulation of enzymes occurs when the binding of an effector molecule to a site that is different from the active site causes a change in the enzymatic activity. This alternate site is called an allosteric site, and an enzyme can contain more than one of these sites. Allosteric regulation can either be positive or negative, resulting in an increase or decrease in enzyme activity. Most enzymes that display allosteric regulation are metabolic enzymes involved in the degradation or...
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Feedback Inhibition00:46

Feedback Inhibition

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Biochemical reactions are occurring constantly in cells, converting starting substances to different products, usually with the help of enzymes that speed the reactions. Without enzymes, it would take far too long for most reactions to occur to be useful to the cell!
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Generation and Coherent Control of Pulsed Quantum Frequency Combs
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Quantum ergotropy and quantum feedback control.

Kenta Koshihara1, Kazuya Yuasa1

  • 1Department of Physics, Waseda University, Tokyo 169-8555, Japan.

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This summary is machine-generated.

Quantum operations can extract energy from quantum systems, but their efficiency is limited. Breaking these limits requires feedback control, offering new insights into quantum thermodynamics and energy bounds.

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Area of Science:

  • Quantum thermodynamics
  • Quantum information theory
  • Statistical mechanics

Background:

  • Understanding energy exchange in quantum systems is crucial for quantum technologies.
  • Quantum operations, including unitary and unital, govern these energy transformations.
  • Ergotropy quantifies the maximum work extractable from a quantum state.

Purpose of the Study:

  • To investigate energy extraction and charging in finite-dimensional quantum systems using general quantum operations.
  • To establish bounds on energy changes induced by unital quantum operations.
  • To explore the role of feedback control in overcoming established energy bounds.

Main Methods:

  • Analysis of energy changes under general quantum operations.
  • Derivation of bounds for energy extraction and charging.
  • Comparison of unital operations with unitary operations and thermodynamic laws.

Main Results:

  • Unital quantum operations' energy changes are constrained by ergotropy and charging bounds applicable to unitary operations.
  • Exceeding the ergotropy bound for unitary operations necessitates quantum operations incorporating feedback control.
  • The ergotropy bound for unital operations on initial thermal states is stricter than the standard second law of thermodynamics without feedback.

Conclusions:

  • Feedback control is essential for breaking established ergotropy bounds in quantum energy extraction.
  • Unital operations offer a tighter thermodynamic bound than previously considered, especially from thermal states.
  • This research advances the understanding of thermodynamic laws in the context of quantum operations and feedback.