Two-photon absorption cross sections of pulsed entangled beams

Area of Science:

• Quantum optics
• Nonlinear spectroscopy
• Quantum information science

Background:

• Entangled two-photon absorption (ETPA) offers nonlinear quantum spectroscopy at low photon fluxes.
• Classical models suggest quantum advantage is lost at high photon fluxes due to accidental coincidences.

Purpose of the Study:

• To scrutinize the assumption that quantum advantage is lost at high photon fluxes.
• To demonstrate that quantum-enhanced absorption cross sections can persist even for very large photon numbers.

Main Methods:

• Utilized a minimal model for quantum light to interpolate between entangled pairs and high-photon-flux limits.
• Analytically derived ETPA cross sections and the intensity crossover regime.
• Investigated the impact of spectral and spatial degrees of freedom and linewidth broadening.

Main Results:

• Quantum-enhanced absorption cross sections persist at high photon numbers.
• Identified conditions under which quantum advantage is maintained across different light intensities.
• Showcased the influence of spectral and spatial properties on achievable enhancement.

Conclusions:

• The classical assumption of lost quantum advantage at high photon fluxes is challenged.
• Quantum-enhanced absorption is viable beyond low photon flux regimes.
• Understanding light properties is crucial for maximizing quantum spectroscopy enhancements.