Charging of a Quantum Battery by a Two-Photon Quantum Pulse

We investigate the charging of a harmonic-oscillator quantum battery by a propagating two-photon quantum pulse coupled through a two-level-system charger. Excitation-number conservation reduces the dynamics to a sequential response of the first and second excitation sectors, whose effective non-Hermitian generators exhibit two exceptional points separating overdamped, mixed, and underdamped regimes. We derive the exact full-charging amplitude and the response-matched two-photon temporal mode that achieves perfect charging in the ideal resonant single-channel model. For experimentally accessible Gaussian pulses, moderate temporal anticorrelation or a finite photon delay can enhance charging, whereas positive correlations generally suppress it. States with equal Schmidt number can nevertheless show different charging efficiencies, demonstrating that temporal-mode structure and response matching, rather than nonseparability alone, determine charging performance.