Single-photon state
= Single-photon state
{title2=$|1_\psi\rangle$}
A <single-photon state> lies in the one-excitation sector of the quantized <electromagnetic field>. It can be a <quantum superposition> over spatial ports or temporal modes while its total <photon number> remains one. Squared coefficients give exclusive event probabilities only when the corresponding wavepacket modes are orthonormal; overlapping temporal histories must be added coherently.