That said, there is reason to believe evolution could have harnessed quantum effects. A leaf, for example, is able to move energy from sunlight into its chemical factories so efficiently that nothing is lost to heat, an efficiency that has eluded all computer simulation and has been attributed to plants’ recruitment of quantum coherence. Similarly, birds can orient themselves by Earth’s magnetic field, travelling thousands of kilometres to return to precise coordinates. This ability may be traced to a protein called cryptochrome,² whose entangled electrons are altered by Earth’s magnetic field, allowing the birds to sense and therefore navigate by it. Furthermore, enzymes speed up reactions faster than is theoretically possible by strictly chemical means, possibly because they allow electrons and protons to tunnel through energy barriers that slow chemical reactions.

Recent evidence contravenes the long-held belief that biology is hostile to maintaining quantum states: nature has ways of engineering quantum advantage without relying on pristine laboratory conditions. Indeed, the biological chaos can be exploited, in much the same way that, in electronics, noise can be recruited to sharpen a signal instead of obscuring it.³

In order to certify the existence of quantum effects in biological systems, researchers will need resources that go beyond what has been necessary for scientific disciplines established so far. Quantum biology requires novel technological tools, conceptual frameworks, and language. These are under development: forums such as the Quantum Biology Gordon Research Conference and the QuEBS: Quantum Effects in Biological Systems workshop series are starting to bring different disciplinary communities together to build a shared conceptual library and a plan for enabling measurement and quantification of effects.

However, in many forms of quantum computing, processors have to be isolated from their environment and cooled to near absolute zero to maintain quantum coherence. “Noise” of any kind tends to cause decoherence, introducing errors or even ending the computation. This is the root of the objection to quantum coherence playing any significant role in warm, wet biological systems.

However, tools are being developed to demonstrate the existence of coherent quantum states in warm systems. For example, nitrogen-vacancy centres, which are single-crystal diamonds with an altered molecular structure, have significant potential as quantum magnetometers for nanoscale phenomena and sensitive field detection. The same is true of naturally occurring boron nitride nanotubes.⁵ These may provide a way to investigate the presence of coherent quantum states and have the potential to investigate the quantum properties of living biological material.

Single-molecule spectroscopy is another investigative technique that has demonstrated the feasibility of revealing signatures of intrinsic quantum coherence. This would be particularly useful in investigations of the quantum mechanisms behind photosynthetic light-harvesting. Another newly developed tool is a mathematical procedure for calculating the exact contribution of quantum coherence in energy transfer.⁶

All of these developments suggest that it may soon be possible to pin down the exact nature of the molecular processes behind some hitherto-unexplained biological phenomena and reveal whether quantum coherence is playing a fundamental role in their operation. However, observing the existence of a quantum state in a biological cell does not constitute proof that biology exploits it for a particular purpose. That would require proof linking the quantum state to a biological function. To achieve a theory of quantum advantage in complex biological systems, therefore, chains of causality must be demonstrated in vivo, preferably within an entire organism.

New experiments are needed to show how quantum processes propagate up to the level of the cell and connect to specific neural, behavioural, or metabolic activities at the much larger scale of the organism. It is critical to show the chain of amplification in a biological system that leads from a quantum process at the micro-scale to improved classical functions at the macro-scale. Ongoing work in this space targets microtubules,⁷ reactive oxygen species, and the mitochondrial electron-transport chain.

It will be crucial to observe a quantum-compatible signal, build a model, and then demonstrate that perturbation of the process leads to loss of biological function.

This opens up the possibility of a symbiosis between biology and quantum technology that could create new scientific and technological frontiers. Living matter may even harbour its own quantum hardware that can be harnessed for biological quantum information-processing or for nanoscale quantum sensing which sheds light on the processes behind complex molecular functions. It may even be more powerful than the quantum information-processing currently under development, naturally harnessing complexity to go beyond the traditional binary-digit form of computation.

Central to this vision is the biological “qubit”. In standard quantum computing, the qubit is the quantum version of the binary digit, or bit. Classical computing bits are either 0 or 1, allowing binary-based mathematical computations. Qubits are a probabilistic combination of 0 and 1, enabling computations that go beyond the mathematical routines available to classical computers.

Molecular systems in biology exhibit properties that, under the right conditions, function as organic qubits: coherent two-state quantum systems embedded in a biological context. Qubits have been created, for example, in mammalian cells,⁸ and may prove useful for magnetic-field sensing and imaging. Unlike the engineered qubits of silicon or superconducting devices, these organic qubits operate at physiological temperatures, are synthesised by cells, and interact directly with biochemical networks, preserving coherence despite the complex intracellular environment.

New developments in quantum computing, where researchers are harnessing qubits with more than two states – “qutrits” with three states and “qudits” with up to seven separate states in superposition – suggest that biology could do the same. When conventional computers try to model complex biological objects such as molecules, they struggle under the weight of computational resources necessary to keep track of the associated components and behaviours. It is possible that our current inability to computationally model complex biological processes may be due to biology’s use of qudits for “high-dimensional” quantum behaviour.

These developments suggest that it may be possible for organic qubits to be identified, isolated, and harnessed as components of biological quantum information-processors, and that quantum sensors may be able to operate inside living systems without disrupting their function.

Developments in this area may help fundamental physics as well as biology and technology. At present, physicists have little grasp of the quantum-to-classical transition that occurs due to decoherence. Investigations of the existence and behaviour of room-temperature qubits in biology may shed light on the quantum-classical boundary that has puzzled scientists for more than a century.