Entangled photon spectroscopy

Abstract

This tutorial outlines the theory of nonlinear spectroscopy with quantum light, and in particular with entangled photons. To this end, we briefly review molecular quantum electrodynamics, and discuss the approximations involved. Then we outline the perturbation theory underlying nonlinear spectroscopy. In contrast to the conventional semiclassical theory, our derivation starts from Glauber's photon counting formalism, and naturally includes the semiclassical theory as a special case. Finally, we review previous work, which we sort into work depending on the unusual features of quantum noise, and work relying upon quantum correlations in entangled photons.This work naturally draws from both quantum optics and chemical physics. Even though it is impossible to provide a comprehensive overview of both fields in one tutorial, this text aims to be self-contained. We refer to specialised reviews, where we cannot provide details. We do not attempt to provide a comprehensive review of all the literature, but rather focus on specific examples intended to elucidate the underlying physics, and merely cite the remaining publications.

Towards Heralded Two-Photon Absorption and Two-Photon Excited Fluorescence for Quantum Microscopy and Spectroscopy

“…Then, the entanglement would not provide a benefit [50]. By harnessing the absorption of only two photons in a heralded setup and by controlling the delay between the two entangled photons it appears also feasible to perform virtual state spectroscopy [51,52].…”

Perspectives for Applications of Quantum Imaging

“…Hence, the penetration depth into tissue is reduced by a factor of . Nevertheless, since the initial proposal several experiments in this direction had been carried out successfully . Yet, all of them suffer from the rather low pair generation rate in the BBO crystals used for photon‐pair generation.…”

“…Nevertheless, since the initial proposal several experiments in this direction had been carried out successfully. [124][125][126][127][128] Yet, all of them suffer from the rather low pair generation rate in the BBO crystals used for photon-pair generation. However, photon pair sources based on SPDC in periodically poled crystals (e.g., ppKTP) not only allow a broader variety in wavelength selection but also tremendously enhance the photon pair rate to 1 × 10 6 counts per mW pump power, [59,129] which can be further increased by at least an order of magnitude by employing waveguide structures within the periodically poled non-linear crystals.…”

Virtual-state spectroscopy with frequency-tailored intense entangled beams

“…1] has allowed us to obtain information about a sample that would not be accessible otherwise. Interestingly, the use of entangled light in two-photon spectroscopy has received a great deal of attention very recently [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] because of the unique phenomena that arise in the interaction of entangled photon pairs with matter. Examples of these effects are the linear scaling of the TPA rates on the photon flux [21], two-photon-induced transparency [22], the ability to select different states in complex biological aggregates [23], and the control of entanglement in matter [24,25].…”