Experimental Bounds on Entangled Two Photon Absorption in Rhodamine 6G

Abstract

Entangled photons have been reported to enhance two-photon absorption by many orders of magnitude. Recent theoretical work predicts smaller increases for common molecular dyes. We present experimental results supporting this claim in Rhodamine 6G.

Entangled two-photon absorption by atoms and molecules: A quantum optics tutorial

“…[ 23 , 24 , 25 ] Accessible textbook treatments are given in the quantum optics text by Loudon [ 26 ] and in the nonlinear optics text by Boyd. [ 27 ] When dealing with short light pulses or light having timefrequency correlations (entanglement), a more detailed treatment is needed, and several such treatments have appeared, a few being [1,10,11,19,20] Figures 1 and 2 define the molecular states of interest and the perturbative sequences for the molecular density-matrix elements leading to excitation by one-or two-photon transitions. Molecular density-matrix elements are given by the total density operator as: ,…”

How to optimize the absorption of two entangled photons

“…The former determines the width of the pump pulse, and hence should be compared to the deviation δ, which sets the width of the optimal two-photon wave function (31), see figure 1(b) and (32). The latter determines the frequency difference between the two down-converted photons, and thus should be compared to the deviation ∆ between the transition frequencies |g → |e and |e → |f , see figure 1(c) and (33).…”

“…In addition, quantum correlations may help to further manipulate optical signals [28,29,30]. Yet, a key problem in the practical application, currently, is the low absorption cross section of many samples [31,32,33,34]. One possible remedy to address this issue and further this field is the shaping of entangled photonic wave functions [35,36,37], to enhance the absorption probability.…”

“…Subsequently, in section 4, we turn to the question of how entangled photons can be optimized for two-photon absorption (TPA) in experimentally realistic scenarios, before we conclude in section 5. (32,33). The widths of the local maxima give a qualitative impression of the nonclassical frequency correlation between both incoming photons.…”

“…(c) Single-photon density (33) derived from (31) upon tracing over the frequency of the partner photon in |Φ(ω 1 , ω 2 )| 2 , for the same parameter values as in panel (b). The double-peaked distributions in (b,c) feature maxima in the vicinity of the first (|g → |e ) and second (|e → |f ) bare transition's (see panel (a)) rescaled frequencies 0 and ∆, respectively, with distinct widths determined by ∆ and δ, see(32,33). The widths of the local maxima give a qualitative impression of the nonclassical frequency correlation between both incoming photons.…”