Abstract
We investigate how entanglement can enhance two-photon absorption in a three-level system. First, we employ the Schmidt decomposition to determine the entanglement properties of the optimal two-photon state to drive such a transition, and the maximum enhancement which can be achieved in comparison to the optimal classical pulse. We then adapt the optimization problem to realistic experimental constraints, where photon pairs from a down-conversion source are manipulated by local operations such as spatial light modulators. We derive optimal pulse shaping functions to enhance the absorption efficiency, and compare the maximal enhancement achievable by entanglement to the yield of optimally shaped, separable pulses.
Highlights
Coherent control generally refers to the manipulation of quantum dynamical processes by suitably shaped control fields or interactions [1,2,3]
The fluorescence signal induced by two-photon absorption of entangled photons is directly proportional to the population of | f 〉 after the pulses have passed through the sample
This condition is satisfied in the limit t − t0 → ∞ of Sec. 2.4, and, maximizing the population is directly equivalent to maximizing the fluorescence rate induced by a flux of entangled photon pairs, and we may write the fluorescence signal as [18]
Summary
Coherent control generally refers to the manipulation of quantum dynamical processes by suitably shaped control fields or interactions [1,2,3] It has found widespread application in the control of chemical reactions [4,5,6,7,8,9], in spectroscopy [10, 11], in laser cooling [12,13,14] or even in quantum information and computing [15, 16]. A key problem in the practical application, currently, is the low absorption cross section of many samples [31,32,33,34], unless the two-photon transition can proceed through near-resonant intermediate states [35] In this case [36], the shaping of entangled photonic wave functions [37,38,39] can enhance the absorption probability.
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