We humans always want to believe that we can overpower nature. However, the reality is that nature outperforms humans in many aspects. Animals' abilities to navigate/orient and photosynthesis are two excellent examples in these aspects. However, the mechanisms underlying them are still unknown. For decades, scientists and researchers have made a lot of efforts to reveal these mysteries in nature. Recently, quantum coherence and entanglement are believed to play a crucial role in such biological systems–avian compass and photosynthesis. Thus, nature might know more tricks to utilize quantum mechanics than humans. Studies on the mechanisms underlying avian compass and photosynthesis are highly able to improve or inspire new technologies in detection of weak magnetic fields and solar cells. In this thesis, the effect of quantum coherence and entanglement in these systems is studied. Based on the studied systems, this thesis falls into two parts: avian compass–radical pair mechanism and photosynthesis–enhancing photocell efficiency via coherence. The radical pair mechanism used to explain the avian compass is studied in the first part. It is demonstrated that Cryptochrome is a suitable candidate of the primary magnetoreceptor, located in birds' eyes. Also, the product yields due to the radical pair reactions are able to act as the direction signal for birds. The long-lived quantum entanglement has presented between the radical pairs. In photosynthesis, quantum coherence has been demonstrated to play an essential role in high energy conversion efficiency. Studies have revealed that the quantum coherence can break the detailed balance, the key factor limiting the efficiency in artificial solar cells. By mimicking photosynthetic complexes, a designed solar cell taking advantage of coherent donors caused by dipole-dipole interactions is able to achieve a higher energy conversion efficiency than the famous Shockley-Queisser limit. Again, more and more evidence has shown that quantum mechanics is able to play a crucial role in biological systems. Quantum coherence and entanglement, as main signatures of quantum mechanics, can be used to explain many astonishing phenomena in nature, such as avian magnetoreception and photosynthesis. Learning from nature can accelerate developments of new technologies.
We humans always want to believe that we can overpower nature. However, the reality is that nature outperforms humans in many aspects. Animals' abilities to navigate/orient and photosynthesis are two excellent examples in these aspects. However, the mechanisms underlying them are still unknown. For decades, scientists and researchers have made a lot of efforts to reveal these mysteries in nature. Recently, quantum coherence and entanglement are believed to play a crucial role in such biological systems–avian compass and photosynthesis. Thus, nature might know more tricks to utilize quantum mechanics than humans. Studies on the mechanisms underlying avian compass and photosynthesis are highly able to improve or inspire new technologies in detection of weak magnetic fields and solar cells. In this thesis, the effect of quantum coherence and entanglement in these systems is studied. Based on the studied systems, this thesis falls into two parts: avian compass–radical pair mechanism and photosynthesis–enhancing photocell efficiency via coherence. The radical pair mechanism used to explain the avian compass is studied in the first part. It is demonstrated that Cryptochrome is a suitable candidate of the primary magnetoreceptor, located in birds' eyes. Also, the product yields due to the radical pair reactions are able to act as the direction signal for birds. The long-lived quantum entanglement has presented between the radical pairs. In photosynthesis, quantum coherence has been demonstrated to play an essential role in high energy conversion efficiency. Studies have revealed that the quantum coherence can break the detailed balance, the key factor limiting the efficiency in artificial solar cells. By mimicking photosynthetic complexes, a designed solar cell taking advantage of coherent donors caused by dipole-dipole interactions is able to achieve a higher energy conversion efficiency than the famous Shockley-Queisser limit. Again, more and more evidence has shown that quantum mechanics is able to play a crucial role in biological systems. Quantum coherence and entanglement, as main signatures of quantum mechanics, can be used to explain many astonishing phenomena in nature, such as avian magnetoreception and photosynthesis. Learning from nature can accelerate developments of new technologies.
Many living organisms can exploit quantum mechanical effects to gain distinct biological advantages. In plants, photosynthesis uses quantum coherence to achieve near 100% efficiency in energy transfer. With advances in experimental techniques, two-dimensional electronic spectroscopy can reveal dynamic processes such as coherence and coupling within a system, and it plays an important role in studying energy transfer in photosynthesis. On the theory side, methods such as the generalized Bloch-Redfield theory and the hierarchical equations of motion are used to model photosynthetic systems. Quantum simulation, as a high-efficiency and low-complexity approach, has also made progress across various platforms in the study of photosynthesis. In recent years, a series of studies has introduced quantum coherence into artificial systems to enhance energy transfer efficiency, laying the groundwork for the design of coherent devices with efficient energy transport. Birds can use the weak geomagnetic field and spin-dependent chemical reactions to detect direction. Theoretical frameworks for animal navigation include magnetite-based mechanisms, magnetoreceptor genes, and the radical-pair mechanism. Quantum simulations of navigation have also advanced on multiple platforms. Inspired by animal navigation, diverse quantum effects have been applied to improve sensing and to support navigation tasks. This paper presents a comprehensive review of progress on quantum coherence in photosynthesis and avian navigation, along with related theoretical methods, quantum simulation approaches, and research on quantum coherent devices.
The radical pair mechanism is one of the two main hypotheses to explain the navigability of animals in weak magnetic fields, enabling e.g. birds to see the Earth's magnetic field. It also plays an essential role in the field of spin chemistry. Here, we show how quantum control can be used to either enhance or reduce the performance of such a chemical compass, providing a new route to further study the radical pair mechanism and its applications. We study the role of quantum entanglement in this mechanism, and demonstrate intriguing connections between radical-pair entanglement and the magnetic field sensitivity of the compass. Beyond their immediate application to the radical pair mechanism, these results also demonstrate how state-of-the-art quantum technologies could potentially be used to probe and control biological functions.
Abstract The lines separating Biology and Physics have started to blur in recent decades, leading to the emergence of the interdisciplinary field known as quantum Biology. This field looks into the possibility that basic quantum mechanical phenomena such as coherence, entanglement, tunneling, and superposition play crucial roles in biological processes that are beyond the scope of classical Physics. Biology has traditionally worked within the parameters of classical mechanics, presuming that delicate quantum effects cannot endure in the warm, humid, and cacophonous environments of living systems. But new findings in fields like photosynthesis, olfaction, avian magnetoreception, and enzyme catalysis indicate otherwise, suggesting that living things intentionally and possibly advantageously use quantum principles. From the earliest speculative theories to the most recent experimental confirmations, this book chapter methodically examines the evolution of quantum Biology. We investigate how the exceptionally high energy transfer efficiency in photosynthetic complexes particularly in the light-harvesting proteins of green sulfur bacteria and plants is supported by quantum coherence. The remarkable speed of proton transfers and enzymatic reactions during DNA replication is also investigated in relation to quantum tunneling. The chapter explores magnetoreception in migratory birds and suggests models in which sensitivity to Earth's geomagnetic field is made possible by radical pair mechanisms influenced by quantum entanglement. We also discuss the intriguing but controversial idea that quantum vibrations improve the human olfactory system's capacity for discrimination. In addition to examining particular occurrences, this research challenges more general theoretical models that seek to balance quantum mechanics with the decoherence commonly observed in biological settings. Recent developments in quantum information theory, biomimetic quantum technologies, and ultrafast spectroscopy are highlighted as essential instruments advancing empirical research. We also critically evaluate the field's methodological difficulties, the skepticism of overly optimistic interpretations, and the significant philosophical ramifications of acknowledging life as a quantum phenomenon. In conclusion, quantum Biology suggests that quantum effects are not uncommon aberrations but rather are an essential part of life, offering not only a fresh perspective for reinterpreting well-known biological processes but also the potential for a fundamental paradigm shift. Quantum biology has the potential to completely transform biotechnology, medicine, and our comprehension of consciousness and the origin of life as experimental methods advance. This chapter highlights the significance of interdisciplinary cooperation in order to completely comprehend the latest discoveries and possible future paths of quantum Biology, highlighting its revolutionary influence on our comprehension of life at the most basic levels. Key words: Quantum Biology, tunneling, avian magnetoreception, enzyme catalysis
The radical-pair mechanism is one of two distinct mechanisms used to explain the navigation of birds in geomagnetic fields, however little research has been done to explore the role of quantum entanglement in this mechanism. In this paper we study the lifetime of radical-pair entanglement corresponding to the magnitude and direction of magnetic fields to show that the entanglement lasts long enough in birds to be used for navigation. We also find that the birds appear to not be able to orient themselves directly based on radical-pair entanglement due to a lack of orientation sensitivity of the entanglement in the geomagnetic field. To explore the entanglement mechanism further, we propose a model in which the hyperfine interactions are replaced by local magnetic fields of similar strength. The entanglement of the radical pair in this model lasts longer and displays an angular sensitivity in weak magnetic fields, both of which are not present in previous models.
Many biological phenomena including avian navigation and photosynthesis manifest quantum coherent effects. In avian navigation, the weak geomagnetic field and spin-dependent chemical reactions are utilized for navigation. As one of the most important energy sources on earth, photosynthesis has always been a point of discussion for scientists. The study of energy transmission in photosynthetic systems can support the design or performance optimization of artificial light-harvesting devices. Currently, the quantum coherent effect has been observed in photosynthetic complexes, and the quantum efficiency of energy transmission in photosynthetic complexes is close to 100%. These important findings prompted many experts in different disciplines to use quantum physical methods to explore the physical mechanism behind the energy transmission in photosynthetic systems and the role of the quantum coherent effect in the exciton energy transmission in photosynthetic complexes. It has been proven that energy transfer in pigment-protein complexes is mainly in the form of coherent energy transfer. Moreover, the importance of the quantum coherent effect in energy transmission has been proven. Furthermore, several researchers have used the quantum coherent effect to improve energy transmission in photosynthetic systems and achieved some progress. For open quantum systems, such as photosynthetic systems, many theoretical methods have been proposed to analyze their quantum dynamics. These theoretical methods can be divided into two categories according to whether they can describe the diagonal term of the system density matrix, namely, coherent and incoherent theories. Moreover, the application conditions of these theoretical methods differ according to their established processes. Recently, with the progress in research, several groups have proposed several quantum simulation methods based on different quantum computing systems, including quantum simulation methods based on nuclear magnetic resonance systems, superconducting quantum circuit systems, and ion trap systems, to analyze the phenomena in photosynthetic systems. Compared with the traditional theoretical calculation methods, these quantum simulation methods have higher computational efficiency and lower computational complexity. This paper mainly reviews the progress in research on quantum coherent effects in photosynthesis and the related theoretical calculation and quantum simulation methods.
Quantum biology is now taken rather seriously. Photosynthesis and avian navigation are two key applications of quantum biology. The basic problem in both cases is posed by the fact that the magnetic interaction energy in Earth's magnetic field is roughly million times smaller than thermal energy. The so called radical-pair mechanism (RPM) was proposed already in the 60's as a possible solution to the problem posed by anomalously large effect in EPR and NMR experiments. According to RPM, a radical pair is accompanied by electron pair, which is in a superposition of spin triplet and singlet states and behaves as quantum coherent system for a time sufficiently long to induce chemical effects. The hyperfine interaction of the members of the electron pair with the nuclei of radicals would amplify the effect. The neutralization of radical pair puts an end to the coherence interaction period. The proposal is that RPM gives rise to chemical compass making possible avian navigation. There is however a problem. RPM has been observed in laboratory only for magnetic fields in the range 1 mT-10 T. Earth's magnetic field is only 2 per cent of the lower bound so that it is quite possible that RPM is not at work. This opens up the door for new quantum physics proposed by TGD based model of quantum biology. In this approach magnetic body acts as as intentional agent using biological body as a sensory receptor and motor instrument. Macroscopic quantum coherence is made possible by dark matter realized as a hierarchy of heff = n x h phases. In this article RMP is summarized and compared with the TGD based vision. Also the possible connection between avian navigation and circadian clock suggested by the fact that both involve photoreceptor known as cryptocrome and a possible connection with gravitaxis are considered in TGD framework.