Theory of the monochromatic advanced-wave picture and applications in biphoton optics

TL;DR

This paper develops a formal monochromatic advanced-wave theory to better understand biphoton states in quantum optics, enabling improved analysis and design of quantum imaging and holography techniques.

Contribution

It introduces a comprehensive formalism for the advanced-wave picture with monochromatic light, extending the understanding of biphoton states beyond simple models.

Findings

The formal theory explains biphoton states from arbitrary crystals and pump beams.

It models biphoton wave functions as impulse response functions for optical setups.

Applications include analyzing quantum imaging and holography with polarization entanglement.

Abstract

Klyshko's advanced-wave picture (AWP) is mainly interpreted by replacing the nonlinear crystal producing biphotons via spontaneous parametric down-conversion (SPDC) by a mirror in quantum imaging protocols with thin crystals, where the biphotons are perfectly correlated in position at the crystal. To better explain the biphoton spatial states produced by arbitrary crystals and pump beams, we develop a formal theory of AWP with monochromatic lights that the conditional wave function of one photon is calculated by propagation, multiplication, and another propagation. The case of more general photon postselection or no detection and the inclusion of polarization are studied. Then, we explain the form of the biphoton state from SPDC with a bulk crystal and its free-space propagation. By treating the biphoton wave function as an impulse response function of a classical optical setup, we analyze quantum imaging with undetected photons and quantum holography with polarization entanglement, where properties like the spatial resolution can be concisely deduced. This method can be employed to design nonlinear materials or novel quantum imaging techniques. Finally, we discuss Klyshko's original proposal beyond monochromatic lights with the Hong-Ou-Mandel effect as an example.