Non-zero variance of the EM field in the |0⟩ state, ⟨E²⟩ ≠ 0, even though ⟨E⟩ = 0. Drives spontaneous emission, the Casimir force, the Lamb shift, and is the seed for Hawking radiation in curved spacetime.
Non-zero variance of the EM field in the |0⟩ state, ⟨E²⟩ ≠ 0, even though ⟨E⟩ = 0. Drives spontaneous emission, the Casimir force, the Lamb shift, and is the seed for Hawking radiation in curved spacetime.