Mandel Q Parameter — Photon Number Statistics

Mean ⟨n⟩: 5 State: Coherent (Q=0) Thermal (Q=⟨n⟩) Sub-Poissonian (Q<0) Fock |n⟩ (Q=−1+1/n) Compare All Run Photon Counter

Mandel Q = (⟨n²⟩−⟨n⟩²)/⟨n⟩ − 1. Q=0: Poissonian (coherent laser). Q>0: super-Poissonian/bunched (thermal light). Q<0: sub-Poissonian/antibunched (single photon emitter, squeezed light). |Q|=1 minimum for Fock states.