Abstract
The interaction between single or a fixed number of photons with a single absorber is of fundamental interest in quantum technology. The harnessing of light matter interactions at the single particle limit has several potential applications ranging from quantum communication and quantum metrology to quantum imaging. In this perspective, a setup for heralded two-photon excited fluorescence at the single absorber level is proposed. The setup is based on a heralded two-photon source utilizing spontaneous parametric down-conversion, entanglement swapping and sum frequency generation for joint detection. This perspective aimed at triggering a discussion about the study of TPA and TPEF with only very few photons. The feasibility of the scheme is assessed by estimating the performance based on state-of-the-art technologies and losses, with the conclusion that the realization appears to be very challenging, but not completely impossible.
Highlights
Maria Göppert-Mayer derived two-photon absorption (TPA) theoretically in her thesis [1] and the first experimental observation of TPA was achieved 30 years later, enabled by the invention of the laser [2]
Two-photon microscopy (TPM) enabled in vivo deep brain imaging, which is of great interest in neuroscience as it made the efficient detection of beta-Amyloid plaque, a protein linked to Alzheimer’s disease, possible [11]
In the setup proposed here, the signal fields from spontaneous parametric down-conversion (SPDC) crystal 1 and SPDC crystal 2 are coupled into fiber optics with an optional integrated optical switch (OS) that is opened when a photon pair is heralded at the SFG crystal
Summary
Maria Göppert-Mayer derived two-photon absorption (TPA) theoretically in her thesis [1] and the first experimental observation of TPA was achieved 30 years later, enabled by the invention of the laser [2]. Teich and Saleh proposed to exploit entangled photons for TPM in 1997 [29] with an ideal two-photon or biphoton source They later extended this idea towards virtual state spectroscopy [30] giving birth to the field of entangled photon or quantum spectroscopy, which has gained a lot of interest since a few years [31,32,33,34,35]. Heralded single photon sources based on SPDC [38] have been demonstrated and Guerreiro et al have done seminal work on detecting weak nonlinear interactions between single photons using a heralded scheme comprising multiple nonlinear crystals [39,40] In this perspective, a scheme for heralded TPEF is proposed utilizing parts of the approach by Guerreiro et al [40] and exploiting other enhancement strategies for TPEF, which has potential applications in quantum microscopy and quantum spectroscopy.
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