Quantum vision is currently emerging as an interdisciplinary field synthesizing the physiology of human vision with modern quantum optics. We recently proposed a biometric scheme based on the human visual system's ability to perform photon counting. We here present a light stimulus source that can provide for the requirements of this biometric scheme, namely a laser light beam having a cross section consisting of discrete pixels, allowing for an arbitrary pattern of illuminated pixels, each having a photon number per unit time obeying a Poisson distribution around the mean. Both the illumination pattern and the photon number per pixel per unit time are computer controlled, offering simple and unsupervised scanning of these parameters. Moreover, infrared light exactly superimposed on the stimulus pattern can be used for acquiring exact information on the illumination geometry on the pupil. The same light stimulus source can be used to advance pupillometry to a higher level of control and precision, as current pupillometers lack spatial selectivity in illumination. We present pupillometry measurements demonstrating the potential of this source to offer a wealth of information on vision and brain function.
Quantum vision is currently emerging as an interdisciplinary field synthesizing the physiology of human vision with modern quantum optics. We recently proposed a biometric scheme based on the human visual system's ability to perform photon counting. We here present a light stimulus source that can provide for the requirements of this biometric scheme, namely a laser light beam having a cross section consisting of discrete pixels, allowing for an arbitrary pattern of illuminated pixels, each having a photon number per unit time obeying a Poisson distribution around the mean. Both the illumination pattern and the photon number per pixel per unit time are computer controlled, offering simple and unsupervised scanning of these parameters. Moreover, infrared light exactly superimposed on the stimulus pattern can be used for acquiring exact information on the illumination geometry on the pupil. The same light stimulus source can be used to advance pupillometry to a higher level of control and precision, as current pupillometers lack spatial selectivity in illumination. We present pupillometry measurements demonstrating the potential of this source to offer a wealth of information on vision and brain function.
It was recently proposed to use the human visual system’s ability to perform efficient photon counting in order to devise a new biometric authentication methodology. The relevant “fingerprint” is represented by the optical losses light suffers along different paths from the cornea to the retina. The “fingerprint” is accessed by interrogating a subject on perceiving or not weak light flashes, containing few tens of photons, thus probing the subject’s visual system at the threshold of perception, at which regime optical losses play a significant role. The name “quantum biometrics” derives from the fact that the photon statistics of the illuminating light, as well as the quantum efficiency at the light detection level of rod cells, are central to the method. Here we elaborate further on this methodology, addressing several aspects like aging effects of the method’s “fingerprint,” as well as its inter-subject variability. We then review recent progress towards the experimental realization of the method. Finally, we summarize a recent proposal to use quantum light sources, in particular a single photon source, in order to enhance the performance of the authentication process. This further corroborates the “quantum” character of the methodology and alludes to the emerging field of quantum vision.
It was recently proposed to use the human visual system’s ability to perform efficient photon counting in order to devise a new biometric methodology. The relevant biometric “fingerprint” is represented by the optical losses light suffers along several different paths from the cornea to the retina. The “fingerprint” is accessed by interrogating a subject on perceiving or not weak light flashes, containing few tens of photons, so that the subject’s visual system works at the threshold of perception, at which regime optical losses play a significant role. Here, we show that if, instead of weak laser light pulses, we use quantum light sources, in particular, single-photon sources, we obtain a quantum advantage, which translates into a reduction of the interrogation time required to achieve the desired performance. Besides the particular application on biometrics, our work further demonstrates that quantum light sources can provide deeper insights when studying human vision.
Nature has been working on single-photon technology for a lot longer than we have, so why not reap the benefits? Taking advantage of the well-studied capability of the human retina for single-photon detection, this project proposes ultrasecure biometric identification based on the perception of weak flashes of light. The authors turn the physics of photon statistics and the related detection by the eye into a quantum parameter-estimation problem, leading to a biometric quantifier. The security of this ``fingerprint'', based on subject-specific optical-loss parameters, can be understood and quantified---and guaranteed---by the physics of quantum measurement.
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.
We discuss our progress towards testing whether humans can see single photons, using a single-photon source based on spontaneous parametric downconversion and techniques from quantum optics. We review the existing evidence on single-photon vision, and show why no previous experiments with classical light sources (or otherwise) have truly been able to test it. We describe the heralded single-photon source we have built, which can be used for a definitive single-photon vision test, and discuss the statistical requirements and challenges of such a test. In pilot studies, we demonstrate that a two-alternative forced-choice design and our observer viewing station can measure the perception of very weak visual stimuli (including the weakest flashes of light ever directly tested, with just ~3 photons absorbed). We present two proposed experiments to test quantum effects through the visual system, which could contribute to our understanding of wavefunction collapse and the quantum-classical transition. We also discuss our work on other questions related to visual perception near threshold, including the length and completeness of temporal summation, which we have investigated in detail with a new experimental paradigm. We found that temporal summation continues for at least 650 ms when photons are delivered at a rate of about 30 in 100 ms, and that the completeness of summation may remain efficient over this window. Finally, we present some preliminary results on how 8- to 13-Hz alpha oscillations in the brain (which have complex effects on neural excitability and visual perception) might impact the detection of few-photon stimuli.
A study published in Nature Communications demonstrated for the first time that humans can consciously detect a single light particle by directing a single photon, controlled by quantum optical technology (SPDC), onto the cornea of human subjects. Breaking the conventional wisdom regarding the necessity of multiple photons for perception, the study showed that subjects directly perceived a single photon with a probability significantly above statistical chance. The study discovered a priming process where the probability of detecting a second single photon is significantly enhanced for several seconds after detecting an initial single photon, proving that the human visual neural network is a marvelous system capable of filtering information at the absolute quantum limit. [Quantum Biology Society] How fine a physical stimulus can human senses detect? In particular, whether our vision, through which we see the world, can perceive the most fundamental physical limit—a single particle of light (single photon)—has been a major subject of debate in the scientific community for over 70 years. While it was known that a single photoreceptor (rod cell) in the retina responds to individual photons , it was conventionally believed that to consciously perceive light, at least a few photons must arrive simultaneously to overcome noise. However, a phenomenal study has been published proving that the human eye and brain can break through this absolute quantum mechanical limit. The paper titled "Direct detection of a single photon by humans," published as an open-access article in the international journal Nature Communications, provides an answer to this fundamental question. A research team led by Professor Alipasha Vaziri and Jonathan N. Tinsley from the University of Vienna, the Research Institute of Molecular Pathology (IMP) in Austria, and The Rockefeller University in the USA, successfully spearheaded this groundbreaking experiment. ■ A Single Shot of Light Created with Quantum Optical Technology To overcome the limitations of conventional light sources, the research team utilized a quantum optical technology called spontaneous parametric down-conversion (SPDC). Through this, they built a perfectly controlled heralded single-photon source and performed over 30,000 rigorous psychophysics-based experimental trials, shooting this single photon into the corneas of subjects inside a pitch-black dark chamber. ■ The Human Brain Performs Quantum Noise Canceling The results were astounding. The subjects accurately identified when a single photon was emitted with a probability significantly above statistical chance. Even though only a minuscule amount of quantum energy struck the retina, the human visual system and neural networks in the brain filtered this absolute minimum unit of information out of macroscopic noise and visually perceived it. ■ A Light Seen Once is Seen Better: The Priming Effect of the Visual System Even more interestingly, the researchers discovered that the probability of detecting a second single photon was temporarily and significantly enhanced within a time window of a few seconds immediately after a subject detected an initial single photon. The researchers analyzed this as a priming process where the presence of an earlier photon temporarily enhances the effective gain of the visual system. This study proves that a living organism's sensory organs are not merely chemical sensors but sophisticated biophysical systems that interact directly with the quantum world, the smallest unit in the natural world. This discovery provides a new understanding of the signal processing mechanisms of brain neural networks and is expected to open the door to entirely new research exploring human vision and the brain using quantum states of light. https://www.nature.com/articles/ncomms12172