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.
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 Recent experiments have demonstrated strong coupling between living bacteria and light. Here we propose a scheme capable of revealing non-classical features of the bacteria (quantum discord of light–bacteria correlations) without exact modelling of the organisms and their interactions with external world. The scheme puts the bacteria in a role of mediators of quantum entanglement between otherwise non-interacting probing light modes. We then propose a plausible model of this experiment, using recently achieved parameters, demonstrating the feasibility of the scheme. Within this model we find that the steady-state entanglement between the probes, which does not depend on the initial conditions, is accompanied by entanglement between the probes and bacteria, and provides independent evidence of the strong coupling between them.