Testing the limits of human vision with quantum states of light: past, present, and future experiments

TL;DR

This paper reviews the history and current research on human vision at the quantum level, demonstrating that humans can perceive single photons and proposing experiments to explore quantum effects in vision.

Contribution

It introduces new experimental approaches using single-photon sources to test quantum effects in human vision, advancing understanding of sensory perception at the quantum scale.

Findings

Humans can perceive single photons.

Single-photon sources enable testing quantum effects in vision.

Proposed experiments include perception of superposition states and Bell tests.

Abstract

The human eye contains millions of rod photoreceptor cells, and each one is a single-photon detector. Whether people can actually see a single photon, which requires the rod signal to propagate through the rest of the noisy visual system and be perceived in the brain, has been the subject of research for nearly 100 years. Early experiments hinted that people could see just a few photons, but classical light sources are poor tools for answering these questions. Single-photon sources have opened up a new area of vision research, providing the best evidence yet that humans can indeed see single photons, and could even be used to test quantum effects through the visual system. We discuss our program to study the lower limits of human vision with a heralded single-photon source based on spontaneous parametric downconversion, and present two proposed experiments to explore quantum effects through the visual system: testing the perception of superposition states, and using a human observer as a detector in a Bell test.