By- Priyanka Khachariya Ph D Scholar and Dr. Sabyasachi Mukhopadhyay, Department of Physics, SRM University-AP (Amaravati)
Biologists and quantum physicists used to be worlds apart for a long time. While biological organisms are warm, untidy, and dynamic, quantum systems require extremely cold temperatures and isolation from any external influence to work properly. The idea of combining the two was simply out of the question.
Yet, in a surprising breakthrough, scientists at thePritzker School of Molecular Engineering, University of Chicago, have brought these two domains together. They turned a fluorescent protein, the same type that makes jellyfish glow, into a functioning quantum bit, as they describe in their Nature article, “A fluorescent-protein spin qubit.” What makes this even more exciting is that they weren’t alone in this pursuit. Around the same time, a team at the University of Oxfordpushed the idea in a different direction, engineering a family of magneto-sensitive fluorescent proteins capable of not just holding quantum information, but also sensing their surroundings inside living cells as they reported in an article titled “Quantum spin resonance in engineered proteins for multimodal sensing.” Together, these two studies suggest that the line between biology and quantum technology is starting to blur in ways that once seemed purely theoretical.
It sounds like a simple experiment in the laboratory, but this technique can help in a whole new way of looking at life. This can be better understood if you get to know about the nature of the “qubit.” Think of a spinning coin, still in the air, neither fully heads nor fully tails. That in-between, delicate state is roughly what a qubit is: a tiny object that can hold information in a way ordinary switches can’t. Your laptop’s bits are locked into either a 0 or a 1. A qubit can hold both at once, which is exactly what makes it so useful for building extraordinarily sensitive detectors, ones fine enough to sense the magnetic field of a single stray electron sitting a few nanometres away.
Until now, the best quantum bits were built from things like a diamond crystal with a tiny defect inside it. Beautiful physics, but not very practical for biology. We cannot simply glue a shard of diamond onto one specific protein floating around inside a living cell. Proteins, on the other hand, are exactly what biology is good at placing with precision. A cell can be instructed, through its own DNA, to build a particular protein and send it exactly where a scientist wants, onto one enzyme, one membrane, one structure, and nowhere else. With this protein being capable of acting as a magnetic sensor, it means that it will combine the precision of biology with the sensitivity of quantum physics in one single form. This will happen because of the spin of the qubit that will be influenced by the magnetic field to change the spin and the energy levels of the qubit. These changes are then measured by using the optical signal of the protein, making it possible for scientists to know whether there are any magnetic fields and their strengths. The protein will not only be emitting light, but it will be acting as a quantum sensor.
The team focused on an enhanced yellow fluorescent protein, a molecule just three nanometres across. These glowing proteins are already widely used by biologists as cellular tags because cells can make them naturally once given the right genetic instructions. What the researchers realized is that these proteins carry a “triplet state “a hidden energy configuration that had never been tapped for quantum sensing
By firing a near-infrared laser pulse, the scientists managed to read the protein’s triplet state and achieved up to 20 percent spin contrast. That means they could tell the difference between quantum spin states clearly enough to use the protein as a qubit.
Microwave pulses were then used to control the spin states, but because quantum behavior is fragile, this part of the experiment required cooling the proteins to liquid nitrogen temperatures. Under those conditions, the protein qubits held their coherence for about 16 microseconds with the help of a technique called CPMG decoupling.
To test real-world usefulness, the team placed the protein qubits inside mammalian cells. Surprisingly, the same quantum properties held up, even in the complex, messy environment of a living cell. They also tried bacteria at room temperature and detected magnetic resonance signals, recording up to 8 percent contrast. These results demonstrated that fluorescent proteins can act as optically addressable spin qubits even inside life itself.
While the Chicago team worked with EYFP, the Oxford researchers took a different starting point altogether — a protein called MagLOV, built from the LOV2 domain and bound to a flavin cofactor. They have used a number of cycles of directed evolution to make this protein more sensitive to magnetic fields and radio frequencies, effectively tuning its quantum behaviour as we would adjust some recipe. What they found out was amazing – MagLOV demonstrated optically detected magnetic resonance in living bacteria at room temperature with a detectable signal from a single cell without any need in any cooling with liquid nitrogen. All of this can be explained by the so-called radical-pair mechanism, which is a quantum interaction between the backbone of the protein and its flavin cofactor making the fluorescence of the protein sensitive to surrounding magnetic fields.
This way the team moved to the practical application of the concept. They showed that the fluorescence signals could be localized spatially using gradient magnetic fields (effectively creating miniaturized genetically encoded MRI). Furthermore, they showed that the protein is capable of detecting the changes in molecular environment, being useful for the lock-in signal amplification for overcoming biological noise and multiplexed imaging, where several signals are read simultaneously. The most telling point, however, is that when subjected to the usual MRI contrast agents, the protein exhibited a dose-dependent change in magnetic properties, which speaks for the possibility of using it as a molecular environmental sensor. While the Chicago team managed to show that fluorescent protein can work as a qubit, the Oxford team demonstrated how it can really be applied and what capabilities it provides in imaging and sensing inside living cells
The thing I find truly charming about how the Oxford team developed their protein is the fact that they did not try to design it molecule by molecule sitting behind their computers. They generated it. They generated thousands of small genetic mutations, measured the sensitivity of each to the switching magnetic field, kept the best ones and repeated the procedure over and over again. After eleven rounds of this, they ended up with proteins so responsive that a single living bacterial cell’s magnetic signal could be picked up under a normal microscope, no special equipment needed
With these engineered proteins, the team then did a few things that are genuinely fun to picture. They mixed two slightly different versions of the protein together in one dish and could tell them apart afterward, purely from how each one flickered in response to a magnet, a bit like recognising two people by their handwriting even though they wrote the exact same word. They built a miniature version of a hospital MRI scanner, using a magnetic field that changed gradually across space, and used it to figure out where clusters of glowing bacteria were sitting inside a three-dimensional sample, essentially an MRI machine that reads out light instead of the usual signal. And they showed that adding a magnetic metal to a solution of the protein made its flicker fade away in a very predictable manner, which is essentially proof that the protein can sense chemically “noisy” molecules nearby, such as free radicals, the same troublesome molecules linked to ageing, inflammation, and cell damage.
It is worth noticing how these two pieces of work fit together, even though the teams worked independently and used slightly different tricks inside the protein. While one paper is essentially a physics paper that demonstrates that the dark state of a fluorescent protein is indeed a legitimate quantum bit, the second paper is essentially an engineering paper that demonstrates that once you have discovered this magnetically sensitive state of a protein, you can actually breed it up and start using it for something practical. Collectively, they lead to the same conclusion: the machinery of fluorescence in fluorescent proteins, which has evolved naturally in nature through millions of years, turns out to be quantum mechanically interesting enough to make sensors out of.
Right now, the two types of protein qubit sensors lag far behind diamond sensors when it comes to raw sensitivity, and that difference is unlikely to be reduced anytime soon. However, the reason why they are interesting is not the high sensitivity but rather the flexibility that they have. As they are made from standard proteins, they can be produced inside living cells, where there is no need for any special equipment at all. This means that one could see processes that would be impossible to observe with the help of diamond sensors – the protein folding process, the behaviour of enzymes, or the beginning of some disease at a molecular level, for example. The researchers from both teams are confident that this is only the tip of the iceberg and that in the future, the physical background would become more precise, the signals would be stronger and more durable, and such sensors could coexist with other types of sensors.
In case the scientists can make advances in this kind of technology, then the effect is going to be felt way outside the laboratory. Picture sensors of a microscopic nature that will be located within the cell, sending information regarding what is taking place at the atomic level; like a mini-MRI. Doctors and researchers could use this to catch disease at its earliest stage,
long before symptoms appear or watch in real time how a new drug affects cells from the inside. It could also change how new materials are designed, taking inspiration from the way proteins naturally organize and assemble themselves. There’s still a long way to go before any of this becomes routine, but the direction is clear, biology and quantum physic
are no longer separate fields. They’re starting to speak the same language, and that’s where the next big discoveries are likely to come from.
To be fair, this is still early, unfinished science. Both of these protein sensors are, for now, far less sensitive than the diamond-based devices physicists already rely on. The signals are faint, they only last a short while, and there is a lot of work left before any of this becomes a routine lab tool, let alone something used in medicine. But five years ago, the idea of using an ordinary, off-the-shelf fluorescent protein as a room-temperature quantum sensor would have sounded like science fiction. Today it is a demonstrated, if early, reality, and it arrived from two different labs at almost the same time, which is usually a sign that a new area of research is just getting started.
Interestingly, this kind of research isn’t happening far away either. SRM University-AP, right here in Andhra Pradesh, launched India’s first Quantum Reference Facility in 2026 and started a Quantum Research Centre that officially includes quantum biology as a research focus. We are also building a diamond qubit lab. So while the world races ahead with protein-based sensors, a university close to home is quietly laying the groundwork for exactly this kind of quantum research.
So the next time you happen to see a glowing green or yellow protein lighting up cells under a microscope, it might be worth remembering that it is not just glowing. Somewhere inside that light, for a brief flicker of a moment, an electron is quietly keeping a private magnetic diary, and scientists have only just learned how to read the first few lines of it.
