What Is This?
Quantum mechanics governs the behaviour of particles at the atomic and subatomic scale. Quantum effects — superposition, tunnelling, entanglement — are supposed to be fragile things that collapse almost instantly when disturbed by heat or interaction with larger systems. At biological temperatures (37°C), warm, wet, and chemically chaotic, they should decohere in femtoseconds. Living organisms shouldn't be able to exploit them.
Except they appear to do exactly that.
Quantum biology is the study of quantum mechanical effects in biological systems. It's a young field — taken seriously only since the 2007 discovery by Graham Fleming's lab at Berkeley that plants use quantum coherence to achieve near-perfect photosynthetic efficiency. Since then, the evidence has expanded: birds navigate using quantum entanglement in their retinas, enzymes catalyse reactions via quantum tunnelling at rates classical physics can't explain, and the smell system may work through a quantum mechanism nobody expected. The deeper researchers look at the machinery of life, the more quantum weirdness they find.^1
This is not fringe science. The journals are Nature, Science, PNAS. The researchers are at Cambridge, Berkeley, and MIT. And the implications — for solar energy, drug design, our understanding of consciousness, and the nature of life itself — are profound enough that the field has attracted serious attention from both physics and biology.
Why Does It Matter?
- It rewrites the physics of life. Classical biology assumes that biological processes can be adequately described by classical chemistry and physics — molecular shapes, chemical bonds, thermal reactions. Quantum biology is showing that this picture is incomplete at best. Some of the most fundamental processes of life — capturing sunlight, catalysing chemical reactions, sensing magnetic fields — appear to exploit quantum properties that have no classical analogue. Life evolved quantum computing before humans discovered quantum mechanics.
- Photosynthesis is ~95% efficient in a way that shouldn't be possible. The most efficient human solar panels hit around 30%. Plant light-harvesting complexes routinely achieve 95%+ efficiency in transferring captured solar energy to the reaction centre. Classical physics predicts this should be impossible — random thermal motion should lose most of the energy in transit. The resolution: quantum coherence. The energy excitation (exciton) exists in a superposition across multiple pathways simultaneously, exploring all routes at once to find the most efficient one. It's quantum computation happening inside a leaf.^2
- Birds may navigate using quantum entanglement. European robins can detect the Earth's magnetic field with extraordinary sensitivity. The proposed mechanism: cryptochrome proteins in their retinas contain electron pairs in an entangled quantum state, created by blue light. The Earth's magnetic field differentially affects the spin states of these entangled electrons, generating a chemical signal that the bird's visual system interprets as directional information. The bird doesn't just sense the field — it may literally see it, as a pattern overlaid on its visual field. If true, this is quantum entanglement being used as a compass by a biological organism.^3
- Your enzymes run faster than classical physics allows. Enzymes catalyse reactions at rates that exceed what's possible given classical energy barriers. The explanation: quantum tunnelling. Hydrogen atoms (protons and hydride ions) tunnel through energy barriers they couldn't classically cross, rather than over them. This has been directly measured in enzymes like alcohol dehydrogenase. The catalytic machinery that keeps you alive is partly quantum mechanical.
- The field may eventually crack how smell works. Luca Turin's vibrational theory of olfaction proposes that smell receptors detect molecules by their vibrational frequencies (a quantum property) rather than their shapes (a classical property). This would explain why molecules with identical shapes but different isotopes smell different — their vibrational frequencies differ. Still contested, but increasingly difficult to dismiss.
Key People & Players
Jim Al-Khalili & Johnjoe McFadden (University of Surrey) — Co-authors of Life on the Edge: The Coming of Age of Quantum Biology (2014), the best accessible book in the field. Al-Khalili is a theoretical physicist; McFadden is a molecular biologist. Their collaboration produced the clearest synthesis of what quantum biology knows and what it suspects.^4
Graham Fleming (UC Berkeley) — His lab's 2007 paper in Nature demonstrating quantum coherence in the Fenna-Matthews-Olson (FMO) complex of green sulphur bacteria launched the modern quantum biology era. The evidence that photosynthesis uses quantum effects to find optimal energy pathways was the field's founding experimental result.^5
Gregory Engel (University of Chicago) — Extended Fleming's FMO findings and has done key work on the timescales of quantum coherence in photosynthetic systems. His lab has pushed the technical limits of ultrafast spectroscopy to observe quantum dynamics in real time.
Henrik Mouritsen (University of Oldenburg) — The leading experimental researcher on avian magnetoreception. His work on European robins has produced the most direct evidence that the radical pair mechanism (and thus quantum entanglement) underlies bird navigation.^6
Klaus Schulten (1947–2016) — Theoretical physicist who developed the radical pair mechanism hypothesis for magnetoreception in the 1970s — decades before there was any way to test it. His computational biology work at Illinois influenced the entire field.
Luca Turin — Biophysicist whose vibrational theory of olfaction remains provocative and unresolved. His story is told in Chandler Burr's book The Emperor of Scent. Whether he's right or spectacularly wrong, the debate has been productive.
The Current State
The field has moved from "probably impossible" to "experimentally verified in several cases, mechanistically understood in some, frontier in others."
Established:
- Quantum coherence in photosynthesis (FMO complex) — verified in multiple labs
- Quantum tunnelling in enzyme catalysis — well-evidenced across multiple enzymes
- Radical pair mechanism as the physical basis of magnetoreception — strong evidence in birds
Actively contested:
- Whether quantum coherence in photosynthesis is functionally significant (i.e., biology evolved to exploit it) or merely incidental (a quantum effect that happens but isn't selected for). A 2020 study suggested the coherence may not be as important as initially thought. The debate continues.
- The vibrational theory of olfaction — some evidence for, some against. Not settled.
- Quantum effects in the brain and consciousness — the most speculative area. Roger Penrose and Stuart Hameroff proposed that quantum processes in microtubules inside neurons are the physical substrate of consciousness (Orchestrated Objective Reduction, Orch-OR). Most neuroscientists are skeptical, but the hypothesis hasn't been definitively refuted.
Why the "decoherence problem" hasn't killed the field:
The standard objection — biological temperatures are too warm and noisy for quantum coherence — turns out to be wrong in interesting ways. Life appears to exploit noise rather than being defeated by it. In photosynthesis, thermal fluctuations may actually assist quantum coherence by preventing the system from getting stuck in local minima. The vibrations of the protein scaffold may be tuned to couple constructively with electronic quantum states. Biology may have evolved to work with quantum noise, not against it.
Applied frontiers:
- Quantum-inspired solar cells — if we understood exactly how photosynthesis achieves 95% efficiency, we could engineer artificial systems that approach it. Current research on "coherent energy transfer" in synthetic materials draws directly on photosynthesis quantum biology.
- Drug design through enzyme tunnelling — understanding how quantum tunnelling affects enzyme catalytic rates could allow design of drugs that modulate enzyme activity through quantum effects, rather than just blocking active sites.
- Quantum sensing technology — the cryptochrome-based magnetic sensing system is far more sensitive than anything humans have built. Engineering synthetic analogs could produce ultra-sensitive magnetometers for medical imaging or navigation.
Best Resources to Learn More
- Life on the Edge by Jim Al-Khalili & Johnjoe McFadden — The essential book. Accessible to non-physicists, thorough, and honest about what's settled vs. speculative.^7
- Royal Society Interface: "The Future of Quantum Biology" (2018) — A key review paper from leading researchers. The best single academic overview.^8
- Frontiers in Quantum Science: "Quantum Phenomena in Biological Systems" (2024) — The most current review.^9
- Jim Al-Khalili's TED Talk: "How Quantum Biology Might Explain Life's Biggest Questions" — 16 minutes, the best accessible introduction.^10
- The Order of Time by Carlo Rovelli — Not quantum biology specifically, but the best living physicist writing about what quantum mechanics actually means for our understanding of reality. Sets the philosophical context.^11