We have seen that our whole knowledge of the external world of physics may be pictured as arising from the impact of photons of energy either on our sense organs or on our physical instruments. As these photons occur in such profusion and variety, it might have been hoped that they would give us an almost perfect knowledge of the outer world. Yet, as a means of acquiring knowledge, photons suffer from one very serious limitation. They are indivisible; no experiment has ever revealed a fraction of a photon or given any reason for supposing that energy can be either emitted or absorbed in fractions of photons. Thus the only means which are at our disposal for the study of physical nature suffer from a certain coarse-grainedness. This is of little consequence as regards direct study by our senses, since these are even more coarse-grained. Each sense has its perceptions limited by a certain “threshold of sensation”, and if the stimulus of a physical effect falls below this, the sense in question registers nothing at all. We cannot experience the sweetness of a single molecule of sugar, nor the smell of a single molecule of musk; neither can we hear a bell at more than a certain limit of distance, nor see a star which is below a certain limit of faintness. In general we cannot experience a single photon; thousands at least are necessary to attain the threshold of sensation.
We have seen that our whole knowledge of the external world of physics may be pictured as arising from the impact of photons of energy either on our sense organs or on our physical instruments. As these photons occur in such profusion and variety, it might have been hoped that they would give us an almost perfect knowledge of the outer world. Yet, as a means of acquiring knowledge, photons suffer from one very serious limitation. They are indivisible; no experiment has ever revealed a fraction of a photon or given any reason for supposing that energy can be either emitted or absorbed in fractions of photons. Thus the only means which are at our disposal for the study of physical nature suffer from a certain coarse-grainedness. This is of little consequence as regards direct study by our senses, since these are even more coarse-grained. Each sense has its perceptions limited by a certain “threshold of sensation”, and if the stimulus of a physical effect falls below this, the sense in question registers nothing at all. We cannot experience the sweetness of a single molecule of sugar, nor the smell of a single molecule of musk; neither can we hear a bell at more than a certain limit of distance, nor see a star which is below a certain limit of faintness. In general we cannot experience a single photon; thousands at least are necessary to attain the threshold of sensation.
When the revolutionary conceptual structure for the description of the physical world which we know as quantum mechanics was first formulated nearly 90 years ago, and its predictions tested in the laboratory, most of the experiments in question were on systems which were both very well characterized and reasonably well isolated from their environments, such as single electrons and atoms, small molecules and near-perfect crystalline solids. While from the very start most physicists have taken it for granted that the formalism of quantum mechanics, when combined with appropriate system-specific information, can “in principle” account for all phenomena occurring in the physical world, including those usually regarded as the subject-matter of biology, until quite recently the overwhelmingly majority opinion has been that in a biological context the role of quantum theory is confined to elucidating the equilibrium structures of the relevant molecules and their reaction processes, and that subtle phenomena such as superposition and entanglement, of which we can now routinely exhibit spectacular effects at the level of a few well-isolated photons or atoms, play at most a very indirect role in any phenomena of biological interest. A major reason conventionally given for this view has been that biological systems, at least working ones, are by their very nature “warm and wet” – a phrase which in the physicist's lexicon translates to “prone to massive decoherence”; it looks as though any interesting superposition, say of different energy eigenstates of one's system, would be rapidly decohered by the ever-present, and usually microscopically very complex, environment.
We have now concluded our summary of the findings of modern physics, and may turn to consider how these findings affect the practical problems of philosophy and of everyday life. But let us first recapitulate the conclusions we have reached in our scientific discussion. Recapitulation Because we are human beings and not mere animals, we try to discover as much as we can about the world in which our lives are cast. We have seen that there is only one method of gaining such knowledge—the method of science, which consists in a direct questioning of nature by observation and experiment. The first thing we learn from such questioning is that the world is rational; its happenings are not determined by caprice but by law. There exists what we have called a ‘pattern of events’, and the primary aim of physical science is the discovery of this pattern. This, as we have seen, will be capable of description only in mathematical terms. The new quantum theory explained in the preceding chapter has provided a mathematical description of the pattern of events which is believed to be complete and perfect. For it enables us—in principle at least—to predict every possible phenomenon of physics, and not one of its predictions has so far proved to be wrong. In a sense, then, we might say that theoretical physics has achieved the main purpose of its being, and that nothing remains but to work out the details.
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
Bohr is said to have remarked that anybody who is not shocked by quantum theory has not understood it. No physicist, however, challenges its practical usefulness in predicting experimental results and providing an explanatory framework for an enormous range of study. Nevertheless, more thoughtful physicists have been astonished and disturbed by what is implied when attempts are made to interpret its meaning. As a result a variety of ingenious, and sometimes bizarre, schemes have been devised since its inception in order to make these implications more acceptable to the scientific mind. Some of these schemes have resulted in proposals which appear stranger than the problems they have been designed to resolve. After some sixty years there is no consensus of opinion upon the solution of the epistemological problems posed. Indeed the debate keeps on resurfacing in the scientific literature and continues to generate library shelves of books. Some progress, however, has been made and the late John Bell himself and the experimental work of Alain Aspect have demonstrated that some epistemological positions cannot be sustained.
It has become ever more clear over the past 70 years that reality is best described by a theory that no one fully understands and which cannot be applied to most everyday phenomena. Quantum theory has been subjected to many stringent tests and all of its predictions, however strange, have always been borne out. Originally developed to account for why atoms do not collapse and why they radiate and absorb energy in discrete amounts (quanta), it has now gone far beyond these rather simple beginnings. It is essentially a mathematical theory, so trying to describe it in words is analogous to transforming a picture into a poem. Inaccuracies, distortions and over-simplifications inevitably creep in. Nevertheless, one can convey the essence of the picture, and that is what is attempted here. Some grasp of what the material world is really like, and of the unfamiliar ways in which it can behave, is probably necessary to reaching an understanding of awareness and is certainly needed to comprehend the experimental evidence set out in Chapter 5.
Abstract Both empirical and theoretical objective science can only access relations, revealing nothing about the intrinsic nature of the entities “in relation”. We typically refer to these entities as “matter”, assuming their nature is irrelevant and that relational structures alone explain all phenomena, including consciousness. This would imply that consciousness arises not from matter itself but solely from its structural configurations. Consequently, if two worlds possess isomorphic structures and obey identical dynamical laws, isomorphic systems within these worlds should be equally sentient or insentient. I demonstrate that if this premise held true, the memories within an observer’s brain would bear no correlation to the external world. Yet since we do acquire knowledge of the external world, structure alone must be insufficient: there exists something beyond relations, the intrinsic essence of the “stuff in relation”. This essence imbues the observer’s structure with sentience, metaphorically “breathing fire” into it. In turn, the observer confers physical meaning upon the world’s structures. Remarkably, this conclusion emerges directly from physics and mathematics. Without acknowledging this intrinsic element, we would be incapable not only of subjective experience but also of acquiring any objective knowledge about the physical world.