Abstract Progress in the experimental nano-sciences and laser cooling has led to the manipulation of material objects with sizes and temperatures such that quantum effects start to appear. This range of sizes coincides with that of the smallest bacteria as well as of the largest viruses, and is often considered to be the boundary between living and nonliving entities. Experiments are rapidly progressing towards putting micro-organisms into quantum superposition states in a controlled manner, resulting in nontrivial quantum effects that we normally do not attribute to living systems. In order to set limits for the occurrence of such effects, I model micro-organisms quantum mechanically and investigate how relevant physical properties are modified from their classical bulk values in the presence of classical self-gravity. The results show that a transition between quantum-like and classical behavior exists right at sizes corresponding to the broad boundary between the smallest bacteria and the largest giant viruses.
Abstract Progress in the experimental nano-sciences and laser cooling has led to the manipulation of material objects with sizes and temperatures such that quantum effects start to appear. This range of sizes coincides with that of the smallest bacteria as well as of the largest viruses, and is often considered to be the boundary between living and nonliving entities. Experiments are rapidly progressing towards putting micro-organisms into quantum superposition states in a controlled manner, resulting in nontrivial quantum effects that we normally do not attribute to living systems. In order to set limits for the occurrence of such effects, I model micro-organisms quantum mechanically and investigate how relevant physical properties are modified from their classical bulk values in the presence of classical self-gravity. The results show that a transition between quantum-like and classical behavior exists right at sizes corresponding to the broad boundary between the smallest bacteria and the largest giant viruses.
The most striking feature of quantum mechanics is the existence of superposition states, where an object appears to be in different situations at the same time. The existence of such states has been previously tested with small objects, such as atoms, ions, electrons and photons (Zoller et al 2005 Eur. Phys. J. D 36 203–28), and even with molecules (Arndt et al 1999 Nature 401 680–2). More recently, it has been shown that it is possible to create superpositions of collections of photons (Deléglise et al 2008 Nature 455 510–14), atoms (Hammerer et al 2008 arXiv:0807.3358) or Cooper pairs (Friedman et al 2000 Nature 406 43–6). Very recent progress in optomechanical systems may soon allow us to create superpositions of even larger objects, such as micro-sized mirrors or cantilevers (Marshall et al 2003 Phys. Rev. Lett. 91 130401; Kippenberg and Vahala 2008 Science 321 1172–6; Marquardt and Girvin 2009 Physics 2 40; Favero and Karrai 2009 Nature Photon. 3 201–5), and thus to test quantum mechanical phenomena at larger scales. Here we propose a method to cool down and create quantum superpositions of the motion of sub-wavelength, arbitrarily shaped dielectric objects trapped inside a high-finesse cavity at a very low pressure. Our method is ideally suited for the smallest living organisms, such as viruses, which survive under low-vacuum pressures (Rothschild and Mancinelli 2001 Nature 406 1092–101) and optically behave as dielectric objects (Ashkin and Dziedzic 1987 Science 235 1517–20). This opens up the possibility of testing the quantum nature of living organisms by creating quantum superposition states in very much the same spirit as the original Schrödinger's cat 'gedanken' paradigm (Schrödinger 1935 Naturwissenschaften 23 807–12, 823–8, 844–9). We anticipate that our paper will be a starting point for experimentally addressing fundamental questions, such as the role of life and consciousness in quantum mechanics.
The question whether quantum mechanics is complete and the nature of the transition between quantum mechanics and classical mechanics have intrigued physicists for decades. There have been many experimental breakthroughs in creating larger and larger quantum superposition and entangled states since Erwin Schrödinger proposed his famous thought experiment of putting a cat in a superposition of both alive and dead states in 1935. Remarkably, recent developments in quantum optomechanics and electromechanics may lead to the realisation of quantum superposition of living microbes soon. Recent evidence also suggests that quantum coherence may play an important role in several biological processes. In this review, we first give a brief introduction to basic concepts in quantum mechanics and the Schrödinger’s cat thought experiment. We then review developments in creating quantum superposition and entangled states and the realisation of quantum teleportation. Non-trivial quantum effects in photosynthetic light harvesting and avian magnetoreception are also discussed. At last, we review recent proposals to realise quantum superposition, entanglement and state teleportation of micro-organisms, such as viruses and bacteria.
The existence of living organisms in the mesoscopic realm may be quite nontrivial and actuallymay emerge from the interplay between quantum mechanics and gravity. On one side, quantumbiology investigates how quantum mechanical phenomena, such as superposition, entanglement,and tunnelling, contribute to biological processes. These quantum effects, once thought to beirrelevant in the “warm, wet, and noisy” environment of living organisms due to decoherence, havebeen found to play significant roles in various biological systems, from photosynthesis to enzymecatalysis. On the other side, gravitational forces have been implicated in the organization ofmicrotubules, which are essential for maintaining cellular structure and function. Recent studieshave demonstrated that gravitational forces can induce three-dimensional chromosomal conformational changes, which are associated with rapid transcriptional responses in human T cells. Sometheories propose that gravity might play a role in decoherence, such as in the Penrose-Hameroffmodel, which proposes that quantum coherence in microtubules could be the basis for consciousawareness and quantum computing-like information processing, with gravity playing a role in thecollapse of the quantum wave function. The model predictions that microtubules can support longrange coherent phenomena have been confirmed by experimental observations of superradiancefrom mega-networks of tryptophan UV-excited transition dipoles, particularly in microtubulearchitectures. Another experimental research highlights that microtubule network exhibits ahierarchy of three-fold resonant frequency patterns across biological scales – from tubulin proteinsto microtubules and neurons. This suggests a quantum-to-classical transition governed by scalefree dynamics, potentially underlying information processing in the brain. A very intriguing fact isthat at the most fundamental level of the origin of life, the standard genetic code, we can observethe scale-free computing that arises from arithmetic regularities of the nucleon numbers related tothe code’s numerous symmetries. Given that some of these symmetries probably originate fromdifferent evolutionary epochs, such scale-free computing may be a latent background mechanismof the organization of the genetic code and therefore relevant to natural computing.
The continuous manifestations of emerging and reemerging infectious diseases across the world is championed by microorganisms particularly, viruses and bacteria. These manifestations consistently keep researchers at work in establishing approaches towards minimising the burden of infectious diseases both locally and internationally. Microorganisms, especially bacteria and viruses, possess very disparate features like the presence of sensors, in-built biological engines, immaculate communication means, processing architecture, among others. Researchers are introducing these biological entities into the quantum theory network where their dynamical physical properties and concepts can be used to develop response mechanisms during infection stages. This article aims to review and present an account of quantum approaches derived from quantum mechanics as an emerging fundamental enabler and a novel concept in the treatment of infectious diseases. It also looks at the possible application of these quantum approaches in revolutionising discovery, development, and production of vaccines at a quantum scale and speed. A descriptive review of the literature was conducted by searching these electronic databases: Web of Science, PubMed, and SciELO. Findings in this article show that through the advent of single-particle approaches and high-resolution techniques, viral dynamics can be scrutinised during and after their assembly towards studying their infection development pathway. Additionally, quantum information in biological entities has been found to provide hereditary information insights supporting genetic studies in relation to infectious diseases. The introduction of quantum-inspired genetic algorithms towards predicting the secondary structures of RNA depicts certain superiority over strategies currently in existence. Ongoing research is putting quantum-based studies in an ideal direction towards shaping the understanding and perhaps treatment of infectious diseases.
Abstract Phenomenological models aiming to join gravity and quantum mechanics often predict effects that are potentially measurable in refined low-energy experiments. For instance, modified commutation relations between position and momentum, that account for a minimal scale length, yield a dynamics that can be codified in additional Hamiltonian terms. When applied to the paradigmatic case of a mechanical oscillator, such terms, at the lowest order in the deformation parameter, introduce a weak intrinsic nonlinearity and, consequently, deviations from the classical trajectory. This point of view has stimulated several experimental proposals and realizations, leading to meaningful upper limits to the deformation parameter. All such experiments are based on classical mechanical oscillators, i.e., excited from a thermal state. We remark indeed that decoherence, that plays a major role in distinguishing the classical from the quantum behavior of (macroscopic) systems, is not usually included in phenomenological quantum gravity models. However, it would not be surprising if peculiar features that are predicted by considering the joined roles of gravity and quantum physics should manifest themselves just on purely quantum objects. On the basis of this consideration, we propose experiments aiming to observe possible quantum gravity effects on macroscopic mechanical oscillators that are preliminary prepared in a high purity state, and we report on the status of their realization. Graphical abstract