Yksittäisfotonilähteen käyttö yksittäisfotonivasteiden mittaamiseen verkkokalvon sauvasoluissa
Jussi Tiihonen
Our eyes are able to encode information from broad daylight down to only a handful of photons, but could we perceive a single photon? For decades the intrinsic Poisson variation of classical light sources has prevented definitive answers to this question. However, recent advances in quantum optics and non-classical light sources have reignited new interest in the question. Studies relying on sub-Poisson light sources have postulated that it is possible to produce sub-Poisson biological response distributions along the visual pathway, and even claimed that humans can perceive single photons. However, unambiguous experimental evidence for the prerequisite of sub-Poisson response statistics in the visual sciences has not been provided, that is, to which extent biological response statistics can differ between Poisson and sub-Poisson stimulation when taking retinal single-photon signal losses into account. In this thesis, we use a state-of-the-art sub-Poisson light source combined with the suction pipette technique to stimulate retinal rods in an axial geometry and measure their single-photon signal losses. We resolve the constraints set by the loss of single-photon signals to biological signal statistics from rods to human psychophysics. We show that due to the loss of single-photon signals it is impossible to distinguish the response distributions originating from Poisson or sub-Poisson light sources in the retina and at the level of perception on a biologically relevant timescale. Our results require fundamental re-evaluation of the previous results relying on sub-Poisson light stimulation in vision.
•Dec 16, 2019•0 citations