The term Quantum biology (Quanten-Biologie) was first used by Pascual Jordan in 1943 in his book “Die Physik und das Geheimnis des Lebens” posing a question “Sind die Gesetze der Atomphysik und Quantenphysik für die Lebensvorgänge von wesentlicher Bedeutung?” (‘Are the laws of atomic and quantum physics of essential importance for life?’) . At that time the question was essentially theoretical in nature as the existing technology didn’t allow it to be perused experimentally. Later Erwin Schrodinger an early pioneer in the field of quantum physics in his book “What is life” (1994) discussed the application of quantum mechanics to solve biological problems. He introduced the idea of an aperiodic that could store genetic information in its configuration of covalent bonds and suggested that mutations might occur due to quantum leaps. With the recent advancement in the field of quantum computing and simulation, quantum biology has developed as a new vision to observe natural phenomenon under the light of quantum mechanics.
It involves the study of biological interactions and phenomenon like enzyme catalysis, photosynthesis and avian navigation under the light of quantum mechanics. As we dig deeper inside the atoms making biological systems, we come across various interactions and mechanisms going within a living cell that make use of quantum phenomenon such as- quantum tunneling, quantum entanglement, coherence and superposition which so far were thought to be relevant to only isolated molecular, atomic or sub-atomic systems or at extremely low temperatures (near absolute zero) and were thus not thought to be applicable to living systems. At this point it is important to make it clear that the word “quantum” in the field of quantum biology does not simply imply quantization but rather refers to a more specific phenomenon. Even though well known in physics and chemistry, it wasn’t till now thought to be of any importance within complex environment of living cells.
One of the well-studied examples of non-trivial role of quantum mechanics in biological system is the process of photosynthesis. It is a highly efficient solar energy harvesting system built from sophisticated molecular machinery of various pigment protein complexes. The precise pathway of the transfer of the excitation energy between various photosynthetic complexes is well studied but the mechanism of how this energy transfer takes place still remains a grey area. In 2007, a group of two scientists led by Hohjai Lee and Gregory S. Engel respectively, suggested long-lived quantum coherence as a possible mechanism to transport excitation energy during photosynthesis. Another example comes from the study on enzyme catalysis. One such study was conducted by Amnon Kohen (1999) where he found that hydrogen tunneling contributed significantly to the enzymatic activity at room temperature. Tunneling refers to the phenomenon where a particle crosses the reaction barrier as a result of its wave nature. It is observed in reactions involving small molecules occurring at reduced temperature. In his study using thermophilic alcohol dehydrogenase, he found H-tunneling occurring at elevated temperature of 65oC in biological system.
In another study, Cristopher C. Page (1999) and group observed tunnelling of electron and protons in enzymes associated with redox reactions. Luca Turin (1996) at University College London proposed that olfactory receptors do not respond to the shape of the molecule but their vibration. He further proposed inelastic electron tunnelling to be a plausible mechanism for transduction of these molecular vibrations in a biological system. Beyond these examples, work of Jianming Cai (2010) and Erik M. Gauger (2011) showed quantum entanglement to play a part in birds navigation. Some migratory birds can sense even very tiny variations in the earth’s magnetic field. In their work they used radical pair model to explain this avian compass. According to the radical pair model, a bird’s eye contains large number of magnetoreceptors at its back. These molecules are coupled anisotropically at quantum level so as to give directionality, giving rise to patterns which are deciphered by the bird and indicate the orientation of the field. They also found that this super-positioned and entangled state is sustained in the living system for tens of microseconds which is far more than the best comparable man-made system.
Quantum biology isn’t just limited to theory but is now finding implications. In 2017, a group of scientists led by Michail Loulakis devised a quantum biometric based on retinal photon counting. Rhodopsin are the principal photodetectors in human eyes which along with the associated photo transducers form an efficient single-photon counter ultimately leading to perception of light. Michail used the quantum statistical property of these retinal photon detectors and proposed secure quantum biometric identification system.
Consciousness has always been a difficult term to be explained by conventional neuroscience. Scientist have constantly engaged with the questions regarding its existence and mechanism. One such scientist, Sturt Hameroff of University of Arizona (2002) proposed quantum coherence and self-collapse (a phenomenon of quantum wave function) are essential for consciousness. He proposed their occurrence in cytoskeletal microtubules and other structures within the neurons. He pointed that the crystal-like lattice structure, the hollow inner core organization of cell function and capability of information processing make these microtubules for quantum effects. He ideated that the conformational state of tubulin is coupled to internal quantum events and interact with other tubulins. He further proposed that the coherent superposition of these quantum-coupled tubulin confirmation state occurs significantly throughout the brain volume and provides global binding essential for consciousness. Though being a possibility, the idea didn’t win much support in neuroscience community.
Quantum biology has come a long way from the insights of the early quantum pioneers of twentieth century. Quantum phenomena such as tunneling and coherence are now widely accepted as being involved in vital processes in living cells such as enzyme action and energy transfer. However, other areas of quantum biology, such as, magnetoreception, occurrence of mutations or olfactory reception still remain speculative as the experimental systems aren’t tractable to precise physical measurement.
The undisputed fact remains that quantum dynamics taking place within the living system has developed over 3.5 million years of optimizing evolution. Life has learned to manipulate these quantum systems to its advantage in ways we still don’t understand. Nature will never stop surprising us, “Life is warm and wet, yet entangled”.