Paul Rand: Imagine a world in which we could see inside a cell with extreme precision, with such detail that we could detect notoriously tricky diseases like Alzheimer's before they progress, and without invasive procedures.

Peter Maurer: And I think this is something, 10 years ago, people would have thought is future, future science fiction, but we are really now turning this into actual proof of concept devices.

Paul Rand: That's Peter Maurer, assistant professor at the Pritzker School of Molecular Engineering at the University of Chicago. Last year, he and his colleagues turned a protein found in living cells into the first biological quantum bit, also known as a qubit. It's a breakthrough that could change life sciences as we know them.

Peter Maurer: We believe that these quantum sensors that we are developing could be a key to develop a new type of technology that could tell us not only where bio-molecules are, but also what has happened to them.

Paul Rand: The discovery of this quantum sensor was named one of the top ten breakthroughs of 2025 by Physics World Magazine.

Peter Maurer: Now, this is where really our work could potentially be a game changer, or one of the aspect where our work could be a game changer. So what we showed is that we can encode a qubit into a protein.

Paul Rand: These new biological qubits could give scientists something they've never had before, a way to see directly inside living cells at the quantum level.

Peter Maurer: But now with these quantum sensors, we can for the first time have an NMR or MRI sensors that are the size of a molecule, and this is where I really get excited about quantum technology.

Paul Rand: So once we measure the world at this level of precision, what kind of scientific or medical problems could we actually address? That's one of the questions that Maurer and his lab is exploring.

Peter Maurer: But the application I'm most excited about, and these applications by the way, in my opinion, completely justify the amount of research we are doing and the dedication of my professional career to it, but I think there may be other application out there that we haven't thought about because we really just started to scratch the surface. There could be maybe even much bigger applications out there, and that's what maybe even excites me most, talking to my friends in the life sciences, what could be really new game changer of these quantum technologies.

Paul Rand: From the University of Chicago Podcast Network, welcome to Big Brains, where we explore the ground-breaking research and the discoveries that are changing our world. I'm your host Paul Rand. Join me as we meet the minds behind the breakthroughs. On today's episode, how U Chicago scientists developed the first biological qubit.

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Before we dive into your research, I'd love to start with some context and some big news because your work was just recognized as one of the top breakthroughs in physics for the year. Tell us about that.

Peter Maurer: My group is a quantum engineering lab, but we are interested in exploring quantum systems in a biological environment to develop new type of sensors. So the work that you're referring to is the development of a new type of qubit encoded in a protein.

Paul Rand: So for folks to really get their arms around what you're talking about, I think it becomes really foundational to understand in as clear or a plain of language as you can, what a qubit is, and why that is just such the essential building block here.

Peter Maurer: Yeah. So a qubit is, in its most abstract form, it's a system, a quantum mechanical system, that can live at the same time in two different states. So there are many different ways how to create such a qubit, and one way is to use actually an electron spin. So an electron, a building block of an atom, it turns out that it has these quantum mechanical properties. You can think of it as a magnetic moment going either clockwise or counterclockwise. The picture is wrong, but it's good enough to understand.

So this magnetic moment can now be in either one of two states. And because it's a quantum object, it can be actually in both states at the same time. So the question is how do you encode such a qubit, such a spin qubit in a system? And we have many different ways how to do that. We can do this in an iron, in an ultra-high vacuum. In an atom, again, in an ultra-high vacuum. They are now some of the most promising building blocks to build quantum computers, but we can also do this in a defect, in an diamond crystal. These are called nitrogen vacancy centers, which have been around for a long time and operate at room temperature.

So more recently, David Awschalom discovered that you can actually also encode this spin qubit in molecules, in a molecular crystal. So very similar to a diamond, but no longer relying on what nature gives you, but relying on what chemists give you. So our system goes even a step further and says let's get rid of the crystal of a diamond, let's get rid of the molecular crystal of this molecular qubit, but let's maybe use a different host. The host that we are using are individual proteins.

Paul Rand: Got it.

Peter Maurer: So the spin physics is very similar, but it's in a protein. And given that's in a protein, some of the spin physics has very different flavors to it which allows us, surprisingly, to get this very long quantum coherence, this very long maintaining quantum properties.

Paul Rand: So in some ways, it sounds like you bioengineered a cell to help measure itself.

Peter Maurer: That's very well put.

Paul Rand: Wow, that is super cool. What was biology, for lack of a better word, already doing on its own or for free that you're building upon?

Peter Maurer: This is the surprising thing here. The protein that we are using is called a yellow fluorescent protein. It's fluorescent because when you shine laser light on it in a microscope, it shines light back to you. It shines back to you light in the yellow part of the spectrum if you shine it through light, so that's what we use for imagining.

So nature had no intent to utilize any quantum-ness in the system. But it turns out by sheer coincidence that once in a while, the system switch into a state where it has a spin, this triplet state that I mentioned before that people usually did not like for microscopy. But it turns out that this triplet state actually has quantum properties very similar to atoms, or these nitrogen vacancy centers in diamonds, or these molecular qubits that David has been developing.

So in some sense, it's kind of a coincidence in my opinion. I don't think that nature uses this for anything useful. But now that we have seen that there are these quantum states, we can actually use some really powerful technologies from nature to improve the quantum-ness of our system, the qubit properties. And this is actually something I wanted to discuss here because it's a really cool idea that could be transformational to quantum technology as well.

Paul Rand: When you started going at this and thinking about how to integrate the work in quantum and biological questions, was there specific questions that you thought it was impossible to answer using standard tools that really captivated you?

Peter Maurer: Yeah. I would say my guide star for my research has been fluorescent microscopy tools are really powerful in life science.

Paul Rand: Now, tell me what those are?

Peter Maurer: So biologists became really good in labeling biomolecules that they want to study with a fluorescent tag. So when you shine laser light on it in a microscope, they light up.

Paul Rand: Got it.

Peter Maurer: And they can actually tell you the position of individual biomolecules with nanometer precision. They can even, when you look at two different molecules and see if they are nearby, you can even learn something about interaction of bio-molecules. But knowing the position is still a far cry from what we would like to know about these biological molecules. Ideally, we would actually like to know what happened to these bio-molecules. Have they been modified in some sense during the progression of a disease, or have they been interacting with a pharmaceutical drug? And fluorophore is fluorescent microscopy technology that is really the workhorse of molecular biology and cellular physiology, it just has a very hard time in answering that. And we believe that these quantum sensors that we are developing could be a key to develop a new type of technology that could tell us not only where bio-molecules are, but also what has happened to them.

Paul Rand: Okay. Most people, including on this show and with your colleague David Awschalom and others, we've talked about all sorts of aspects of quantum computing. But your specifically, as you're mentioning, talking about quantum sensing. Can you just tell us in plain language what quantum sensing is?

Peter Maurer: Yeah. So let's start with these qubits. These qubits, they are really sensitive to perturbation from the environment. And if we can measure these perturbations, how they impact the qubit precisely, then we can learn something about the environment. And so here, in this measurement process, we really rely on technology that was pioneered by our colleagues in atomic clock, in the engineering of atomic clock.

Paul Rand: Okay.

Peter Maurer: Atomic clocks, listeners may have heard, is this really amazing technology that can measure time with a precision that is really unmatched in nature. So they can tell us a precision of 1 in 10 to the -21. So that's about, if you switched on an atomic clock at the birth of the universe, it would be now off by less than .1 second.

Paul Rand: Wow.

Peter Maurer: So we can use these spectroscopic techniques, these quantum controlled techniques that people have developed for atomic clocks and translate those on measurements of our qubit, and now not to measure time, but to measure other perturbations like magnetic fields, like electric field, temperature, forces, pressure. And these are really things that are really difficult otherwise to extract in biological measurement, but they could really hold the key to understanding what happens in signaling pathways, what happens to postulation or modification of proteins.

Paul Rand: Okay. So how is sensing, as you're talking about it, different from imaging or microscopy?

Peter Maurer: Yeah. So again, imaging or microscopy kind of tells you where individual biomolecules are, but it's not very good in telling you what happened to these biomolecules. So now what we are doing is by sensing-

Paul Rand: So let's pause on that for a second. It can tell you where they are, but not what happened to them?

Peter Maurer: That's right, yeah.

Paul Rand: Okay, got it.

Peter Maurer: And we also would like to know if a biomolecule, for example a protein, has undergone a modification and became from something that is useful for a cell to something that is diseased and causes a problem to cellular function. But it's often really difficult to do that with existing fluorescent microscopy technology.

Now quantum sensors, they can measure magnetic fields. Once you can measure magnetic fields, you could look actually at very different type of signatures. You probably know about magnetic resonance imaging.

Paul Rand: Of course.

Peter Maurer: In fact, you had recently a guest talking about-

Paul Rand: That's right.

Peter Maurer: ... magnetic resonance imaging. And so, this magnetic resonance imaging was very well explained in that podcast session, rely on magnetic field measurements. Now those sensors usually fill up an entire room. That podcast was talking about a sensor that fills up a chair.

But now with these quantum sensors, we can for the first time have NMR or MRI sensors that are the size of a molecule, and this is where I really get excited about quantum technology. So generally, you can build sensors that can be in principle really powerful, but very sensitive, but they are bulky and they are difficult to integrate into your target system.

Now we are not the first group by a long shot that is developing quantum sensors to study biological systems. In fact, kind of the technology that people have been using as qubits are based on small pieces of diamond called nanodiamonds.

Paul Rand: Okay.

Peter Maurer: Nanocrystals that are small enough that they can be up-taken by a cell. But the problem is once you have these nanodiamonds in a cell, you quickly realize that they are not that useful for sensing or that they have severe limitation for sensing because their size is 10 to 20 times bigger than your average biomolecule that you want to study. And furthermore, it's really difficult to bring this nanodiamond into the right location within a cell.

Now, this is where really our work could potentially be a game changer or one of the aspect where our work could be a game changer. So what we showed is that we can encode a qubit into a protein. So a protein is a particularly type of biomolecule. Each of our cell has about 20,000 different type of proteins. And so these proteins are the size of a few nanometer in size, so about 10 times smaller than nanodiamond. But what's most important is that molecular biology has become really good in inserting the gene that encodes a desired protein into living cells. And so what the cells do then is they express that protein that we use as a quantum sensor and they not just express it, but they also make sure that these proteins are deterministically placed in the right location within a cell. And this is far from what the quantum diamond sensor ever could achieve in my opinion.

So we are 10 times smaller allowing us to get much closer, and we have this ability for the first time to genetically encode our quantum sensors.

Paul Rand: Wow, okay. So tell us, if you can, of what kind of signals can quantum sensors detect, especially as you get down to the size you're talking about, that traditional tools have not been able to focus on?

Peter Maurer: Yeah. It sounds a little bit cheesy, but I would really say the sky is here the limit. So these qubits, as mentioned before, they are really sensitive to perturbation in the environment. And when we build a quantum computer, we go really through a large extent to exclude magnetic field, electric field, temperature, pressure, forces to not perturb these quantum states, these qubits.

So now we can turn it around and say, okay, maybe we engineer our quantum system in such a sense that it's mainly sensitive to a magnetic field that we are interested in. That encodes this information that you usually get from an MRI system, but at the nano scale, at the scale of an individual molecule inside of a cell at the deterministic location. Or maybe somebody else is interested in measuring the irons around a protein, a target protein, called the hydration sphere. And those electric fields is something that our quantum sensors could very likely detect.

Another direction is force sensing. We currently really don't have good force sensors, but we do know, and U Chicago is here actually one of the pioneers. We do know that forces are really important in how tissue organizes, how cells organize in tissue. How cancer propagates, actually. And if we have now a sensor that can be placed with molecular precision into a cell, into a tissue, and we can measure which molecules are sensitive to a strain and facet, maybe we can learn something where things go wrong and cancer propagates.

Paul Rand: Can you help me understand why it's so hard to measure things inside a living cell?

Peter Maurer: Yeah. So cells are highly complex systems. They consist, as mentioned before, out of 20,000 different type of proteins. And if you look at all the post-translational modifications or all the modifications that can happen to these proteins, you're going to valid 100,000, maybe even in the millions. It depends a little bit who you ask, and this is also a test to how difficult it is to study these post-translational modifications. But we really know that these modifications, these post-translational modifications are ruling biology.

Paul Rand: Okay. You have described some of the quantum sensors as being quiet. What does that mean for them to be quiet and why does that matter?

Peter Maurer: Yeah. So qubits are very sensitive, as mentioned, to perturbations from the environment. That's why they are good sensors. But it's really kind of a trade-off, so usually when people build a quantum computer, they have to cool down, as mentioned before-

Paul Rand: Yes.

Peter Maurer: ... their system to near absolute zero or put into an ultra-high vacuum. So what we showed for the first time is that we can take proteins, these building blocks of cells which usually, nobody would consider them to be as a quiet or low noise systems, can actually turn those into qubits with coherence properties very similar to what people are currently using to build quantum computers. For example, the technology that IBM and Google is using to build a quantum computer is called a superconducting qubit. It was actually awarded the Nobel Prize this year.

Paul Rand: Yeah.

Peter Maurer: So these superconducting qubits have coherence times, maintain their quantum properties, at timescales that are very similar to our protein qubits.

Paul Rand: If you're interested in learning more about the world around you or just yourself, check out another U Chicago podcast by the title of Knowing. Every week, Professor Eric Oliver interviews writers, academics, artists and other interesting people about the ideas they're generating to help us better understand the world. Stop guessing and start knowing what it's all about with Knowing, part of the University of Chicago Podcast Network.

One of the things that I kept coming across is a lot of people seem to think that quantum sensing is really the most mature part of the quantum field.

Peter Maurer: I would subscribe to that statement definitely. A good example is atomic clocks, that I mentioned. So atomic clocks have brought us GPS two decades ago. So quantum measurements has already shaped our ability to perform measurements in technology and in science. And I think we are now really starting to see, we're at the threshold of seeing changes in the life sciences as well where quantum technology really could become a game changer.

Paul Rand: Explain in more detail, if you could.

Peter Maurer: So far, we've always been talking in our conversation now, and also actually in the field, how quantum technology could be used to perform measurements in biological systems and advance biotechnology, for example.

Paul Rand: Yes.

Peter Maurer: But I think we could actually now turn, ask the reverse question. Can we use biotechnology to advance quantum technology? And let me explain a little bit what I mean by this.

So when we engineer quantum systems, this qubit system, we actually use a top-down approach. We say, "Okay, we know what makes up this qubit and we know what leads to loss of its quantum property, and so let's maybe use a clever way to engineer better materials, or better vacuum chambers, or go to lower temperature to improve on that properties." But it really relies on us first knowing what leads to the loss of quantum information and then engineer our system in a way to make this better.

Now, biology is actually really good in optimizing systems without knowing the fundamental principle of it, doing basically a black box optimization.

Paul Rand: Okay.

Peter Maurer: So evolution is the key word here. So biology does not know how our body works. Nevertheless, through the process of evolution, through the process of picking out systems that have a higher survivability, nature was able to go from an unstructured soup in an ocean to single cells, to fish, to human beings.

Paul Rand: Right.

Peter Maurer: This was done not with starting from higher principles, was not guided by a deeper insight. It was really guided by a black box optimization. And now I think we can use for the first time this type of selection, this type of natural selection, this type of black box optimization to improve properties of our qubits. That's kind of an amazing idea in my opinion.

Paul Rand: Yeah.

Peter Maurer: We can now use a very complex system that we maybe never going to be able to understand from first principle, but we can just mutate the gene that underlies the information encoding the protein and pick out among hundreds of thousands of different variants, the genetic modification that leads to a better qubit. And then use that as a starting point for a new route of mutation. And if we do that a couple of times, we can maybe get a qubit that is orders of magnitude better than what we have now. And this is something that we are actually starting in our lab here at the University of Chicago to pursue.

Another direction, in my opinion this is really going to be something that really could inform and transform quantum technology, this black box optimization of these really complex systems. Another idea where actually biotechnology could really overcome a longstanding roadblock in quantum technology is self-assembly.

Paul Rand: Self-assembly?

Peter Maurer: Self-assembly. So I mentioned at the very beginning of our interview that I kind of got disillusioned with quantum computing-

Paul Rand: Right.

Peter Maurer: ... during my PhD. And now, biology can actually not make trillions of identical copies with tens of nanometer precision, but biology can make trillions times trillions of identical copies with atomic precision. So we could now think of using maybe self-assembly, so using the molecular biological machinery of a cell, to assemble arrays of spins, arrays of qubits that we really could never do with diamond-based technology.

Paul Rand: Okay, okay.

Peter Maurer: I don't think we're going to build a quantum computer with this, just to be upfront.

Paul Rand: Okay.

Peter Maurer: But I think we can use it to build a quantum simulator. And this may be actually anyway the more interesting application of a quantum computer, simulated [inaudible 00:27:45] quantum system.

Paul Rand: Tell me what you mean by quantum simulator?

Peter Maurer: So a quantum computer is kind of a universal term to solve certain tasks exponentially faster.

Paul Rand: Right.

Peter Maurer: Now finding what kind of tasks that a quantum computer can solve faster is actually a big theoretical challenge that people are very actively pursuing. There is a small number of application knowns, but it looks like the biggest application are actually not to perform a computing task, not to divide numbers by each other, but maybe to simulate a system that could allow us to learn something about the more complex system in nature or complex physical system. So this class of applications are called quantum simulators. That's where actually many of the quantum computing applications, academically at least, are aiming at, building these quantum simulators.

So one of the class where quantum simulators could be really interesting in is studying many spins coupled to each other where you have very interesting quantum states that we can never solve on a classical computer and where we don't have the theoretical tools to study them yet. So people use, again, these molecules in ultra-high vacuum and they do really amazing work with that. People do use defect in diamond, also amazing work with it, but they all run into a limitation when it comes to scale, how many spins it can involve and with positioning with nanometer precision. And this is something where maybe these protein qubits and self-assembly, this molecular machinery, could really become a game changer.

And I think this is something that really starts to excite me beyond sensing, that maybe we can really utilize these decades of advances in biotechnology, this multi-trillion-dollar industry in biotechnology, and use it to advance quantum technology. And I think it's really a two-way street here. We have quantum technology adding sensing in the life sciences, but the biotechnology could also aid quantum technology so there could be some really interesting feedback loop as well.

Paul Rand: Conceptually, how could this sensing and better measurement help us detect disease better and come faster to a breakthrough?

Peter Maurer: I'm not promising that quantum sensing is the silver bullet and replacing all the really powerful technologies molecular biologists have. I think that we can detect structural changes or the addition of phosphate groups to proteins in a living cell and with that understanding, signaling pathways, and with that understanding how diseases progress or how pharmaceuticals change progression of a disease, that this would be really powerful. Because at the moment if you want to study these kind of modifications, you really have to almost obliterate the cell and put it into a mass spectroscopy device which is highly destructive.

And again, it's interesting from very fundamental biological question to really discovery of new pharmaceuticals. And at the moment, we just don't have the technology to do this non-invasively.

Paul Rand: Can you help us understand the types of early signals that cells give off before symptoms start to show up? It's almost like listening to your car and you start hearing, well, there's a noise that happens when you know the brake linings are getting too thin.

Peter Maurer: Yeah, yeah, yeah.

Paul Rand: So you know. So are there other symptoms or signals that you're beginning to sense are happening inside cells that are indicators that there's something not working the way it should be?

Peter Maurer: Another completely different technology is something that my group is pursuing with a lab in oncology. We are developing diamond quantum sensors that can be put onto the tip of a surgical device, a laparoscopic device, an endoscopic device, something like this. Or a fiber, something like this. And maybe can perform, provide us with pathological information-

Paul Rand: Wow.

Peter Maurer: ... that we don't get with current fluorescent imaging technology.

Paul Rand: Okay.

Peter Maurer: Again, because quantum sensors measure in an orthogonal space to what your typical fluorescent label or your imaging technology would do.

So these are things that we really start now to we have very concrete ideas and we start to explore with our friends in medicine. And I think this is something 10 years ago, people would have thought is kind of future.

Paul Rand: Yeah, yeah.

Peter Maurer: Future science fiction, but we are really now turning this into actual proof of concept device.

Paul Rand: When we start thinking of the opportunities that exist once we can measure the world at this level of precision, what kind of scientific or medical problems become more open to us to try to solve that may not have existed previously?

Peter Maurer: Yeah, that's really the great question here. Some of the examples I just gave are examples where I really think we are going to be utilizing this in the future heavily. One is this post-translational modification of a protein. The other one are these medical devices, like measuring changes of small molecule concentration after an injury or during an inflammation, or differentiating cancerous from non-cancerous tissue and giving more informed pathological information. So these are things where I really see, in my opinion, it's clear the path forward-

Paul Rand: Okay.

Peter Maurer: ... to that application. But the application I'm most excited about, and these applications by the way, in my opinion, completely justify the amount of research we are doing and the dedication of my professional career to it. But I think there may be other application out there that we haven't thought about because we really just started to scratch the surface. There could be maybe even much bigger applications out there. And that's what maybe even excites me most, talking with my friends-

Paul Rand: What you don't know yet.

Peter Maurer: ... in the life sciences. Exactly, the life science, what could be really new game changer of these quantum technologies.

Lea Ceasrine: Big Brains is a production of the University of Chicago Podcast Network. We're sponsored by the Graham School. Are you a lifelong learner with an insatiable curiosity? Access more than 50 open enrollment courses every quarter. Learn more at graham.uchicago.edu/bigbrains. And if you like what you heard in our podcast, please leave us a rating and a review. The show is hosted by Paul M. Rand and produced by me, Lea Ceasrine, with help by Eric Fey. Thanks for listening.