Meaning of quantum field | Babel Free

Definitions

A quantum operator-valued function of (any point in) space.

Equivalents

Examples

“In Chaps. 3, 4, and 5, we saw⟳ that for each spin⟳ type⟳, the Schrödinger picture wave⟳ equation for a state and the Heisenberg picture wave⟳ equation for the associated quantum field had the same form⟳. In the former case, the wave⟳ equation solution was a state, i.e., a particle wave⟳ function. In the latter, the wave⟳ equation solution was a quantum field, i.e., an operator that created and destroyed states. For free scalars, this equation was the Klein-Gordon equation; for spinors, it was the (no interactions) Dirac equation; and for massless vectors (photons), it was Maxwell’s equation (sourceless, in terms of A#92;mu).”

“The result⟳ is zero expectation value for φ, and this would be true for whatever state, including the vacuum, that we choose⟳. This effectively means that we would measure⟳ nothing if we tried to measure⟳ the quantum field φ. The field itself is unmeasurable.”

CEFR level