Is the Electromagnetic Field a Classical or Quantum Field?

dilna
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how we can differentiate classical and quantum fields?i searched everywher..but i did not get a satisfactory answer
 
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In QFT the fields are operators that obey a commutation relation.
 
electromagnetic field is a classical field or quantum field?in quantum we speak in erms of photons...if we go for second quantisation to electromagnetic field what we will get??
 
dilna said:
electromagnetic field is a classical field or quantum field?in quantum we speak in erms of photons...if we go for second quantisation to electromagnetic field what we will get??

Um... there is a Lagrangian that gives the electromagnetic field, working with this field classically one obtains a classical field theory (Maxwell's equations, etc.), if one instead applies canonical quantization to this Lagrangian one gets a quantum field theory (Quantum Electrodynamics). Second quantization IS quantum field theory, the excitations in this case are photons.
 
Not an expert in QM. AFAIK, Schrödinger's equation is quite different from the classical wave equation. The former is an equation for the dynamics of the state of a (quantum?) system, the latter is an equation for the dynamics of a (classical) degree of freedom. As a matter of fact, Schrödinger's equation is first order in time derivatives, while the classical wave equation is second order. But, AFAIK, Schrödinger's equation is a wave equation; only its interpretation makes it non-classical...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA
Is it possible, and fruitful, to use certain conceptual and technical tools from effective field theory (coarse-graining/integrating-out, power-counting, matching, RG) to think about the relationship between the fundamental (quantum) and the emergent (classical), both to account for the quasi-autonomy of the classical level and to quantify residual quantum corrections? By “emergent,” I mean the following: after integrating out fast/irrelevant quantum degrees of freedom (high-energy modes...
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