If you have even a passing interest in your health, you can’t spend long on social media before the algorithm brings you into contact with the infamous Q-word. Are you in touch with your quantum energy fields? Could you benefit from a consultation with a quantum dietician?

A dismissive snort is fully justified. But all the woo around “quantum therapies” can make it hard to talk about science that is much more serious. In recent years, clinical research has suggested that exposure to light, as well as electric and magnetic fields, could help to treat everything from acne and hair loss to wounds and cancer.

These therapies don’t necessarily involve quantum mechanics in any meaningful way. Still, there are hints from parallel experiments in test tubes that life might respond to electricity and magnetism via quantum effects – at least on some level. “We have something that works; we don’t really know why,” says Margaret Ahmad, a photobiologist at Sorbonne University in France who studies how electromagnetic fields affect living organisms.

All this ties into an old debate about whether life is too warm, wet and messy for subtle and fragile quantum effects to have much bearing on biology. “Researchers have never been able to unambiguously prove or refute that,” says Clarice Aiello at the Quantum Biology Institute in California. “This is the crux of what we’re trying to do.” Because if quantum states can persist long enough in living cells to matter, that could give us a whole new approach to medicine that complements – and in some cases might sidestep – the use of drugs.

To begin making sense of this tangled thicket of bona fide research, pseudoscience and wishful thinking, we first need to understand what quantum biology is. All matter and energy, whether in living cells or dead chemistry, is fundamentally quantum. At this level, what we tend to think of as particles behave more like smeared-out clouds of possible states described by a wave function, a mathematical formula that defines the odds of finding a particle in a particular state when it is observed and forced to “pick” just one way to be.

Quantum effects are phenomena that wouldn’t happen if classical particles and fields were the end of the physical story. That definition casts a wide net, encompassing everything from the mere existence of molecules to exotic phenomena like entanglement, in which two particles essentially behave as one linked entity. This also makes it hard to know what counts as “quantum biology” – even for quantum biologists, says Gregory Scholes at Princeton University. “Quantum biology isn’t just a bin where you put all stuff that you don’t understand.”

To bring order to this chaos, Aiello separates quantum biology into a hierarchy. At the most mundane level, quantum mechanics explains how atoms link up into molecules. “Yay! Biology is quantum!” jokes Aiello. “That’s not what I care about, but it’s one level.”

At the next level are quantum phenomena that boil down to the particles involved being very small. For instance, quantum tunnelling allows small objects, like protons and electrons, to appear on the other side of energetic barriers that classical particles can’t cross. The smaller the particle, the more likely tunnelling is to occur. Researchers have shown that quantum tunnelling helps plant enzymes, which speed up biochemical reactions, to find their binding sites. These are undoubtedly quantum effects, says Scholes, but “I think when you ask somebody in the street to imagine quantum biology, it would be much more ambitious”.

The upper levels of Aiello’s hierarchy involve more sophisticated kinds of quantumness that arise from long-lived quantum states, which don’t happen just because something is very small. At one level, there is superposition, which describes how quantum objects exist in a combination of their possible states – in some sense, they are both here and there at the same time until observed. These states in superposition interfere with each other, adding up and cancelling out like overlapping waves of water or sound.

The classic double-slit experiment illustrates superposition: if you fire a particle towards a barrier with two slits, it will act like a wave – in a superposition of possible states – and behave as though it had passed through both slits at once. But if you observe the particle as it passes through a slit, the superposition collapses and you see the particle in just one place.

Entanglement is even trickier than superposition, since it involves getting at least two quantum particles to interact in a way that forces their wave functions to depend on each other. After two particles have been entangled, observing one tells you what you would observe if you could see the other, and vice versa – even if they are separated across vast distances.

Quantum biologists have been disappointed by supposedly higher-level quantum effects before. The incredible efficiency of photosynthesis was once thought to rely on superposition, but the quantum physics involved turned out to be subtler, falling somewhere between the levels of superposition and tunnelling in Aiello’s hierarchy. It involves “quasiparticles” called phonons, which carry the energy of molecular vibrations. In photosynthesis, these quasiparticles help light-harvesting proteins shuttle around the energy they absorb from sunshine more efficiently.

Still, there is encouraging evidence that higher-level quantum effects could play roles in life. Migratory birds are thought to take advantage of superposition to navigate using Earth’s magnetic field. This involves a quantum property called spin, which interacts with magnetic fields. Birds have specialised proteins called cryptochromes in their eyes, and when light strikes them, it excites pairs of electrons into quantum states in a superposition between two possibilities: matching spins or mismatched spins.

While in superposition, the electrons interact with Earth’s magnetic field in ways that change the likelihood of ending up with mismatched or matched spins. Cryptochromes behave differently in chemical reactions depending on their state, which effectively turns a magnetic signal into a chemical one – a kind of quantum internal compass that only works thanks to superposition.

So, there’s quantum, and there’s quantum. On what level should we think about light therapies? These originated in the late 19th century when physician Niels Ryberg Finsen, who had a rare metabolic condition, noticed that his symptoms eased in the sun. Finsen took light into the clinic, where he used beams of ultraviolet light to cure skin diseases. The breakthrough won him a Nobel prize in 1903 – just one year before his untimely death.

The Nobel committee remarked that light therapy had “opened a new avenue for medical science”, but until recently that avenue remained largely untread. Now, there is a growing number of claims that light can be used to grow hair, reduce blood glucose levels, lift depression, stall Alzheimer’s disease, heal wounds, speed up recovery from stroke and even treat erectile dysfunction.

The evidence for some kinds of light therapy, also called photobiomodulation, is stronger than others. Weak laser light is becoming a standard treatment for oral mucositis, an inflammation of the mouth that is caused by some cancer treatments. On the other hand, it has been relatively easy to get medical devices based on LED lights approved by the US Food and Drug Administration, since they were thought to be harmless, which can lend credibility to unproven – and sometimes downright dubious – treatments.

“There are so many crackpots out there,” says Ahmad. Some researchers suggest that these therapies work because certain wavelengths of light stimulate a particular light-sensitive protein in mitochondria, which handle lots of important jobs in cells. But there are a lot of unknown steps between “stimulating the mitochondria” and, say, regrowing hair. Ahmad thinks it is unlikely that any real effect of light therapy will come down to a single protein, especially given how many wavelengths of light have purported effects.

Electromagnetic therapies

Scholes suspects that photobiomodulation acts on lower levels of quantumness – or at most, at the middling quantumness of photosynthesis, which is a known light-driven process – or simply at the level of normal chemistry, rather than the level of superposition and entanglement. In fact, he has been working to show that classical systems made of many interacting parts, such as organisms, can sometimes mimic quantum effects without involving any truly quantum physics at all.

Compared with photobiomodulation, which focuses on visible and near-visible wavelengths of light and has been around for about a century, therapies based on electric and magnetic fields are relative newcomers. Researchers in Singapore are developing a magnetic therapy intended to be used alongside chemotherapy for treating breast cancer. And a device called Optune is approved for medical use in the US, Canada, the European Union and Japan to treat specific brain and lung cancers with swiftly alternating electric fields. Optune’s effectiveness is supported by several clinical trials – although many in the medical community are sceptical of the evidence and patient groups have raised concerns about side effects and impacts on quality of life.

The case for higher levels of quantumness in magnetic therapies is, perhaps, stronger thanks to the large body of work on birds seemingly navigating using Earth’s magnetic field and artificial quantum sensors that work on a similar principle. Aiello says it is plausible that treatments based on magnetism take advantage of a similar quantum mechanism involving pairs of quantum spins in superposition.

Yet it is possible that quantum mechanics isn’t involved at all – merely involving light or electromagnetism doesn’t make something meaningfully “quantum”. Optune’s hypothesised mechanism, for instance, seems perfectly classical, says molecular biologist Callum Jones at the University of Sheffield, UK. (Jones has worked on research funded by Optune’s manufacturer.) Alternating electric fields are thought to scramble the electric fields that organise protein filaments involved in cell division, and as cancer cells divide faster than healthy ones, they could be more vulnerable.

Whether based on light, magnetism or electric fields, treatments have clearly sped ahead of theory, resulting in a jungle of different therapies developed by trial and error. This lack of standardisation could help explain the inconsistent results in photobiomodulation studies.

Ahmad says even tiny tweaks to the doses used in a treatment – shining a light for 5 minutes instead of 10, say – can turn a strong response into no response. For instance, she found that in human cell cultures, light can reduce acute inflammation, like the kind triggered by severe covid-19 infections and during sepsis, but only with the right dose. Without knowing how light therapies work, studies often produce more questions than answers. “The challenge now is to get that active [mechanism] so that you can intelligently and reliably apply it,” says Ahmad.

Alzheimer’s disease

Coming at the problem from another direction, quantum biologists looking for high-level quantum effects hope their work could one day lead to novel health treatments. In 2024, Philip Kurian at Howard University in Washington DC published evidence of surprising phenomena that seem to depend on quantum entanglement. In lab experiments with biomolecules – rather than living cells – Kurian and his team found that networks of tryptophan amino acids, when scaffolded on structures called microtubules, behaved as a kind of collective quantum fibre-optic network.

These “mega-networks” seem to be entangled so that they behave like one huge, spread-out quantum entity. Individual tryptophan molecules naturally absorb ultraviolet photons and re-emit them at lower-energy wavelengths as fluorescent flashes, but do this much faster when acting as a quantum collective, says Kurian. Instead of twinkling on and off individually, the synchronised amino acids shine like bulbs on a string of lights that all turn on together in a bright flash.

Ultraviolet photons are emitted naturally by certain metabolic processes, especially when cells are stressed, which can wreak biochemical havoc. So, Kurian thinks this “superradiance” effect could protect cells by efficiently absorbing ultraviolet light. More speculatively, he suggests that cells, including neurons, could use superradiance to transmit information much faster than chemical signalling between neurons. “There’s this huge world, this vast quantum realm that classical neuroscience doesn’t consider,” he says.

Kurian hopes that understanding these processes could lead to new treatments for Alzheimer’s disease. Like microtubules, the amyloid fibrils that are associated with Alzheimer’s are covered in tryptophan, and recent theoretical calculations by Kurian and his colleagues suggest that amyloid tryptophan networks should be even better at absorbing ultraviolet light than those on microtubules. Kurian posits that accumulation of amyloid protein fibrils in the brain could be a defensive response to cope with damaging ultraviolet photons released by metabolically stressed cells – rather than being purely a cause of the condition, as was previously assumed. This could explain the limited efficacy of drugs developed to treat Alzheimer’s by breaking up amyloid fibrils.

However, Scholes isn’t entirely convinced by Kurian’s case for a quantum effect. “It is an interesting idea,” he says, “but it’s difficult to know if one can actually measure the superradiance.”

Even if effects like the one Kurian is studying don’t ultimately turn out to involve high-level quantum phenomena, suggestive results, whether from test tubes or clinical studies, are enough to conjure visions of a future in which we might treat illness or tune our health with beams of light or magnetic fields – although in a fashion that is far more targeted and well-tested than any magnetic bracelet or LED lamp that you might find online.

All these approaches to healthcare are markedly different to treatments rooted in the biochemistry of pharmaceutical drugs. We are only just beginning to extend our understanding of health to include the physical forces at work in life. And on a practical level, clinical trials are costly and drug-makers have little incentive to develop a treatment based on cheap materials and simple technologies they can’t patent easily, says Ahmad.

More fundamentally, quantum biologists still have a big task ahead of them: to prove that higher-level quantum effects play meaningful roles in biological processes. So far, the only level of quantum biology that has resolutely been shown to matter in living cells is the trivial level of chemistry, says Aiello. She hopes to change that in her lab by designing instruments sensitive enough to pick up on minute magnetic fields in living cells.

Whatever researchers find, it will doubtless be less dramatic than the many sensational “benefits of quantum energy” touted by charlatans. But the search will inevitably challenge us to reimagine cells not just as life, but as living physics.