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Vlatko Vedral, "Portals to a New Reality: Five Pathways to the Future of Physics" (Basic Books, 2025)
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A
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B
Welcome to the New Books Network. I'm your host, Gregory McNiff, and I'm excited to be joined by Vladko Vidral, the author of Portals to a New Five Pathways to the Future of Physics. The book was published by Basic Books in the United States in November of 2025. Vladko Vidral is a professor of physics at the University of Oxford, known for both his theoretical work and experimental collaborations on quantum information and entanglement. He is also the author of Decoding Reality, as well as several textbooks on quantum physics and general relativity. He lives in Oxford, England. I selected Portals to a New Reality because it explores how quantum information might unify the deepest divides in modern physics, from relativity to gravity to the nature of time itself. Vladko's ideas push beyond interpretation toward a new way of thinking about reality as information, not matter or energy. I came away from reading the book with a renewed sense that physics is not just about equations, but about understanding reality itself as an evolving web of relationships and information. Hello, Vodko. Thank you for joining me today to discuss your book.
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C
Hi, Greg. Thank you for having me on your podcast.
- [02:18]
B
Vodko, why did you write Portals to a New Reality? And who is the target reader?
- [02:23]
C
Maybe to answer the second question first. I always imagine my teenage self, maybe 16 year old, which is maybe when I started to really get into physics and become interested in physics. And I always imagine that kind of reader, someone who is clearly already curious about science and about physics maybe in particular, but they don't need to know much about it at all. So I think my book doesn't require any in depth understanding, understanding of any of the concepts that I discuss. The reason why I felt it was the right time is because whenever I listen to a discussion, whether it's a podcast or a program about physics, I get the impression that many of these discussions claim that somehow physics is becoming more boring. There are less profound and fundamental things happening in physics. We haven't had a new revolution in 100 years or so, and somehow I could not identify with that at all. In fact, I spent 90% of my time probably doing research. And I think we're at a very exciting place now, very exciting junction. And I felt that there was a great story to be told about it. And so that's the key thesis, really, that we are in fact, on the verge of a huge breakthrough in physics, and in fact, probably within a decade or so of discovering a new theory in physics.
- [04:20]
B
Excellent. Before we discuss the thesis of your book, could you briefly describe a few terms? Superposition, the uncertainty principle, and entanglement.
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C
Excellent. These are the key principles really, in quantum physics. So the first maybe is the most fundamental one, which is called the superposition principle. And it's maybe the Richard Feynman called it, the only mystery in quantum physics, really. And it's the possibility of every quantum object, and I will say a little bit about it, to be in a state which involves different positions at the same time. So if you take an atom, for instance, and we've tested this with atoms, and every atom can exist in a multitude of different locations simultaneously. And it's not just atoms that's the exciting part. In fact, anything we've tested obeys this superposition principle. So basically, we've taken particles of light, photons, we've certainly tested the subatomic world, and we started moving towards more and more complicated molecules, which is the exciting bit. So there are molecules with hundreds of thousands of atoms, and in fact, even they behave in this way that they can exist in many different locations at the same time. So the quantum superposition is really the key property that distinguishes quantum behavior from any classical behavior. Anything in Newtonian physics really does not have this property. Or classical objects cannot do these things. The second thing that you mentioned was entanglement, and that follows directly from the Superposition principle, in fact. Which then is applied to more than one particle, if you like to think about it. So one atom can exist in many places at the same time. Another atom separately, can exist in many different places. But when you put them together. And that's the thing that Schrodinger, Even Schrodinger, an Austrian physicist. Actually one of the pioneers of quantum mechanics. He pointed out. He said if you take these two atoms together. Then together they can exist in many different states. But they can exist in a very funny way. That if one atom is in one place. The other atom is also in that place. And when the first atom is in a completely different place. The second atom mirrors perfectly this behavior. And it's also in this other place. And actually, this property is completely independent. Of how far these objects are from one another. Which is what many people, I think, initially, even Schrodinger. Thought that this was absurd, paradoxical. That there must be something wrong with quantum mechanics. And actually, we've tested that as well. And we are now confident that's a true property of all of the systems we've tested. And the last thing, again, intimately connected. And I think probably it's the first thing you would read about quantum mechanics. If you open almost any account. Would be the Heisenberg uncertainty principle. And this is intimately connected to both of these, the superposition and entanglement. And what it says, really, is that unlike in the classical world. Where you can simultaneously know and quantify all physical properties of your system. So if you have a classical particle. You can measure where it's located. You can measure how quickly it's going. You can measure how much energy it has. And all of these things, we think, hold simultaneously for this classical particle. In quantum mechanics, this is impossible. And that's why it's called the uncertainty principle. Because it suggests that the better I know the position. The more I confine a quantum particle to one place. The less I will know how quickly this particle is moving. In fact, the same is true for energy. So the better you know, one property. Suddenly all of the other properties become much fuzzier. And, in fact, Heisenberg said that you can never go beyond this limit. Which you can quantify mathematically. And that's basically the Heisenberg uncertainty relation. So it's very unusual that even though we think that these properties do belong to atoms, molecules, photons. All of these quantum objects. Somehow it's weird that we cannot ever think of them as being true simultaneously. And that's the uncertainty principle.
- [09:34]
B
Excellent. Thank you. You begin the Book by saying physicists are stuck today or sort of at a crossroads. Could you expand on that?
- [09:42]
C
There are two reasons for that as far as I'm concerned. One, one has. So what I meant by being stuck is that we had two revolutions in physics in the 20th century. The first one was general relativity, which Einstein came up with, maybe it took him about 10 years to get there between 1905 and 1915. And ultimately he came up with a theory that describes. Is the best description of gravity. And this applies to very large objects. We know that if we want to describe planetary motions, stars, even galaxies, ultimately even cosmology, the whole universe, we actually always resort to the general theory of relativity. And that's a completely different domain to the domain that the other theory. Somehow in physics, we need two theories to describe the full reality. And the other theory, of course, being quantum physics. And quantum physics applies in the opposite regime. A domain of tiny objects where basically gravity doesn't really matter that much. Gravitational force would be so small between two atoms that in fact, no one has been able to even measure that experimentally. So the reason why I said that we are stuck is that it seems that we have been unable to test the common ground of these two theories. And actually it's not even clear to anyone how we should approach this. Should we apply quantum principles that we discussed to gravity as well? Does gravity need to become quantum mechanical? That's one option. Should it be that quantum mechanics need to be modified, in fact, to account for. To take into account gravity? That's another possibility. And then the third possibility would be that there is even yet a bigger theory that somehow contains quantum mechanics and general relativity as special cases. And the main reason why we haven't been able to make any progress, I think is simply that we haven't had the right technology to do this. So that's the number one reason. And this changed rapidly with quantum technologies. So I think sometime in the late 90s, when we realized that quantum computers could really be made in large scale, quantum computers, we started to develop solid state technologies like superconducting quantum bits. There was a huge, almost an exponential increase in experimental activities. At some point in the industries became interested, and now they're investing billions and billions of dollars. I would say if you look at companies like Google, Microsoft, at the governmental level as well, Many countries are involved in this race. And these technologies, of course, are primarily focused at the applications that quantum technologies give us. But people like me, in fact, are extremely excited because I think it's exactly the technologies that are being developed now that we can then apply to test our basic theories. And I think now is the right time. It seems to me now we have the right degree of sophistication that we could probe. Some of these questions that I think would tell us, would answer at least the question that I mentioned, whether gravity needs to be quantum. The second reason why I thought we were stuck is because, and that's in fact how I start my book by, in this issue, is because I think we've had wrong, predominantly wrong interpretations of quantum mechanics, what quantum mechanics is really telling us. So the dominant view, I should just mention it very briefly, we could go more into that if you like. But the predominant view is the so called Copenhagen interpretation. That's because of Niels Bohr, the originator, one of the pioneers again of quantum mechanics, who was from Copenhagen. And this is how we teach quantum mechanics to our students. This is how most popular books approach quantum mechanics. And I simply think, I think it's not just a misleading view of quantum mechanics. I think it's ultimately even provably wrong, actually, that if you really follow it through, sticking to all the tenants of Copenhagen, you will actually end up concluding something wrong. And I wrote the book to say that we should actually challenge that view and that I felt that quantum mechanics is telling us something completely different. Actually.
- [14:56]
B
You propose quantum information theory as the means to reconcile these different interpretations or theories regarding the micro and the macro, relativity, quantum mechanics. Could you, and this is a major theme of your book, could you describe quantum information theory?
- [15:16]
C
That's the key. And it goes back to logic, interestingly enough. So the standard classical concept of information that we all have, as soon as someone says information, the first thing you think of are bits of information. And in fact, this goes back even to probably Aristotle, ultimately, who developed some of these basic ideas, Aristotelian logic. But it took a long time to formalize this mathematically. I think ultimately it was George Boole, the Boolean logic, as we call it, an English teacher in the 19th century, who really wrote down all the algebra necessary for bits. And actually what was interesting then is that anything you could in principle do in mathematics, anything you can calculate, anything that even a computer, classical computer could actually process, boils down to manipulations of these zeros and ones. So you could think that behind classical physics, even certainly behind classical computation, are these bits that are encoded into two distinguishable states. You can call one of them the state 0, the other one is state 1. Now, the key difference with quantum information is that and goes back exactly to what we discussed, the superposition principle is that in quantum mechanics, and I will give you an example, because I think it will make it clearer what I mean. In quantum mechanics, these logical bits could be also all the states in between the state 0 and the state 1. So it could be any superposition of the logical 0 and the logical 1 with any weight, if you like, attributed to the state 0 and any other weight attributed to the state 1. So one way to visualize this is to go back to the picture of atoms, I think, that we all learned in school already, which is the electrons which exist around this nucleus. And you can use this. Take a single electron, you can use it to encode information in the following way. That's just one way. There are actually many ways to do this, and in fact, all of them are being pursued now in various places. But one way to think about it is if the electron is closer to the nucleus, you can label that as a state zero. And if the electron is further away from the nucleus, you can call that the logical state one that encodes one. And now, the beauty is that in quantum mechanics, by shining the appropriate laser, you have to choose the right color of the right frequency of the laser, the time, the duration of the pulse, and all of that. But if you do that properly, you can actually make the electron exist closer to the nucleus and further away from the nucleus at the same time. So now, why is this amazing? It's amazing because if you extrapolate this and if you start to involve more and more atoms, more and more quantum bits, suddenly, rather than manipulating one sequence of bits at a time, which is what a classical computer would be doing, in quantum mechanics, you can do all of these computations simultaneously, because your quantum bits exist in all of these logical values, in a superposition of all of these logical values at the same time. And this was realized maybe in the 80s by various people, I think, Richard Feynman, David Deutsch here in Oxford. They pointed out that actually, if you use quantum computers, you can suddenly do things exponentially, more efficiently than with classical computers. And that's what really led to this amazing technological and experimental set of developments that enable us to be here. So somehow, quantum information is fundamentally different to the information that we perceive at our level. Obviously, our perception and our brain evolved in a predominantly classical world because we are large systems, we are macroscopic, and therefore, at our level of perception, we can afford to ignore these kind of superpositions. But once you get to the world of. Of atoms, then, in fact, superpositions and entanglements and the uncertainty principle are the norm. That's the norm. That's how everything at that level really behaves. And suddenly all of these exponentially many computations open up to us. And again, even though I've emphasized now the technological advantages, what that signaled to me and people like myself that actually this is a great tool to understand physics itself, that it's much better to talk about quantum measurements in terms of quantum information, which is really what's happening there, rather than thinking that quantum measurements are extracting classical information. So my book argues that we should never. We should actually avoid using classical concepts as much as we can, ideally completely, and really view the whole universe really as processing quantum information.
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B
Yeah, that's excellent. And I should say at one point in the book, you say, interpretations matter, and your view is, obviously, we need the right interpretation. And quantum information theory does that. I want to move into the five portals or experiments you propose, but I would like you to briefly describe Q numbers. I'm just going to read a quote you have. Everything in the universe is characterized by Q numbers. Each Q number is really a collection of states and measurements. And here we're probably talking about the measurement problem. And measurements are only correlating individual states of different Q numbers. For laymen, what are Q numbers?
- [21:42]
C
A quote is beautiful, I think. And you chose the key quote. I think that perfectly summarizes exactly what I think is the. What I think quantum mechanics is telling us about. About reality. So to explain what Q numbers are, incidentally, terminology goes back to Dirac, Paul Dirac, an English quantum mechanic who worked at the same time. So he's one of the five people that are usually credited for discovering quantum mechanics. Heisenberg maybe is the person who used Q numbers in his paper. He was the first person to use them, but he didn't call them like that. There were all sorts of names that people used at that time. And I will explain that briefly now. So what Heisenberg discovered, remember, he was trying to explain spectra of atoms. So that means if you shine some light on an atom, it will speak back to you. If you like, it will shine some light back. And what people found confusing 100 years ago or so is that the frequencies that you observe when atoms speak back are very specific, discrete set of frequencies. So there are many frequencies that never occur. And if you come to this problem from classical mechanics, it's extremely confusing because classical physics would say, well, you should be able to observe any vibrational frequency of these atoms. So it was a big mystery why Only some frequencies. And so Heisenberg had an ingenious idea. He said what we should do is the following. We shouldn't change necessarily the classical laws of motion. So if you think about Newton's laws, Heisenberg said, they're okay. We can probably keep them as they are. But what we must do is the usually so in classical physics, these laws are obeyed by numbers, by normal numbers, which is. Dirac would call them C numbers, classical numbers. So if you take, for instance, that distance equals to velocity times time, then in classical physics, distance would be one number. Let's say five meters. Velocity would be five meters per second. Time would be one second. All of these are numbers. What Heisenberg suggested, and that looked extremely weird. The paper is extremely confused. Must have been extremely confusing to people at the time. What he suggested is instead of using a single number for each of these properties, you must use a table of numbers. Schrodinger called these things catalogs of information. So actually, it's an array of. It's an infinite number by infinite array of numbers that you must associate with each of these, with the position, with the speed of a particle, with energy of the particle. Each of them becomes a quantum number. So these quantum numbers are these arrays of ordinary numbers, and you must specify them all at the same time. You can already see that this happens to be the root of the superposition principle, actually saying that every system has a multitude of possible positions, not just one. So that's what Heisenberg was discovering. And the next immediate big surprise that he realized it took him about two years to understand all of that, is that unlike in classical physics, where if you first multiply the position by the velocity, or if you first take the velocity and multiply by position, in classical mechanics, this makes absolutely no difference, because three times five is the same as five times three. Or if you first measure the position of a moving car and then you measure the speed, presumably you will get exactly the same answer if you just exchange the order of these. But to his big surprise, these tables of numbers, these Q numbers, had a different, completely different property that, in fact, the order in which you multiply them makes a big difference. So whether you first just specify or measure a position and then you measure the velocity, you will get a completely different answer to if you do it the other way around. And in fact, this is the core of the Heisenberg uncertainty principle. Doing it, one order produces one kind of uncertainty. Whereas if you flick. If you flip the order over, then you get a different kind of uncertainty. So These Q numbers, that's the gist of them.
- [26:44]
B
It. And is he using vectors there that non multiplicative properties is Heisenberg.
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C
Exactly. These Q numbers, you can think of them as matrices. Matrices, exactly. And what they act on are vectors which are then the states of your system. It's exactly that kind of mathematics that becomes relevant.
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B
Perfect. I interrupted you. Please continue.
- [27:06]
C
No, please, that's it. So these Q numbers, like I said the stunning thing. And you see, it's always the question you face when you really need to come up with a new theory. Of course Heisenberg understood that much of classical physics is still correct in its own domain. It's just that in some of these new problems that people came up with with, you simply couldn't get anywhere. You just couldn't measure these kind of spectra, atomic spectra with classical physics. And the first question then is what needs to be thrown away? And I think you require a lot of creativity, a lot of physical intuition, ingenuity. You need to be very brave as well, because you could make big mistakes when you do something like that. So basically the idea there was that he said that. And I'm not going to modify the laws of dynamics. I think they are completely fine, I don't need to tweak with them. But the entities that obey these laws need to be upgraded from the normal C numbers, from the real numbers, if you like, into these Q numbers. And that triggered the whole revolution subsequently.
- [28:24]
B
Great explanation. Professor, we're going to move into your experiments. But you do have a philosophical, I should say the book is philosophical, with some of your insights around quantum physics. And I do want to ask you about two in particular. Specifically you say quantum physics is, quote, I should say it seems strongly on the side of the becoming. What do you mean by that?
- [28:46]
C
Yes, I think this is another very big discussion. In fact, in most sciences I think this occurs, and you're right, that philosophers worry about, about these things. So the question somehow is really whether we should be thinking of the universe as static. And again, all of these views go back to the ancient Greece. Probably Parmenides was the philosopher who even came up with all sorts of logical paradoxes to suggest that motion, any kind of change, any kind of dynamics, is just pure illusion. He just thought that everything that can happen has already happened. And somehow maybe our consciousness takes us from one event to the next event. But in fact all of these things already exist in a completely static universe. The opposite philosophy to this, and maybe we credit Heraclitus with that, that everything always changes. You Cannot step into the same river twice. Heraclitus would say actually that reality is in fact all about dynamics. That change is the key property of the universe. It's not static at all. In fact, you can never capture all the properties of the universe properly if you think of it as a static entity. And in physics we discover this very. Actually we discuss this very frequently. What is the right philosophy, if you like, that corresponds to quantum mechanics. Now it seems to me that quantum mechanics is very dynamical as a theory. It seems to me that every time you make a measurement, and I think we will go briefly into my view of what it means to measure something quantum mechanically. It seems to me that genuinely new quantum information gets revealed to us. Something that didn't exist before. So this kind of static picture where things are already out there and we are just kind of uncovering what. What's already there and there is nothing new. It seems to me it's completely inappropriate to how quantum mechanics works.
- [31:02]
B
Fascinating. I want to ask you a follow up question that I really think gets to the heart of the book. On the one hand, you write, quantum physics isn't really random at the level size of the whole universe. In fact, it is fully deterministic. On the other hand, in discussing the development of quantum physics, you note that quote, uncertainty is a fundamental feature of the universe. Can you help us reconcile these two statements? Namely that on one hand the universe is deterministic, but on the other hand uncertainty is embedded within quantum physics. As you say, a fundamental feature.
- [31:39]
C
Excellent. It's the key question, actually. And in fact I think it's exactly here that it matters how we account for this. It seems to me that if you don't for this dichotomy almost sounds like a contradiction, which is why I wanted to put it that way. You could say, wait a second, how can you say that at some level is deterministic, but at some other level, within this deterministic level, actually there is a genuine novelty, real randomness, real surprise. And that's the beauty of it, that actually it really is like that Feynman always, you know, Feynman, who himself I think had many, many nice quotes about quantum mechanics. He always said it's like walking a tightrope. It really is. If you make a slight wrong assumption, it's probably going to lead you astray and you will never recover from that. So how is that possible? It's possible precisely because. So what I'm arguing against is, and again this would be the conventional view of quantum mechanics is that when you measure a system in a superposition. Frequently, the language we use is that we say we collapse the superposition. We get rid of quantumness. And we obtain one of the outcomes. So when I look at an atom in many different positions at the same time. What I get when I do my experiment is to ask where the atom is. I only get one of these positions. I never see an atom in many different places at the same time. Now, I think that's a wrong language. Because Q numbers never disappear. You can never get rid of a Q number reality. Q numbers are always there. And they simply always describe. All the properties that you can think of. Pertain to whatever the physical system is that you are looking at. So you can't say, I measure the position. And now I destroy the Q number. That pertains to the position of this particle. That simply doesn't make any sense. Despite the fact that we use it. And sometimes it works in practice. And it's okay to use that as a shortcut. So what I think happens, and that's the key now, that if you use this language. Then the outcome is completely random. And, in fact, quantum mechanics itself says that. It says whenever you engage with the atom. Or any other quantum superposition. You will never be able to predict which of the outcomes you will get. So this is this genuine randomness. And in fact, technologically speaking, these are the best random number generators. People use quantum superpositions measurements to get random numbers these days. So you can never. Let me put it even more strongly. If you could tell which of the outcomes you would get. You'd be violating Heisenberg's uncertainty principle. It simply clashes with the basic rules of quantum mechanics. It's impossible. So now I want to link it to determinism, because. Exactly. So now how do I get determinism? You get determinism precisely because the way you should think about the measurement. Is that the Q numbers of the measure. Whoever does the measurement. And by the way, in my book. I argue very strongly against the special place for observance. So I don't mean that you need a human being. Or you don't even need a living system. Frequently you don't even need a macroscopic system to do this. This. But you need a system that has Q numbers. And these Q numbers can get correlated. With the Q numbers of the system that you are measuring. So a measure is simply another system. That has enough quantum capacity. It has enough of these Q numbers. That it can properly get correlated. To extract the information that you need from the other system. And so these Q numbers never vanish. But that leads us to an amazing conclusion, namely that all outcomes happen. It's just that you simply in one of these branches, become aware of one of these outcomes. But the Q number reality is telling us that the other outcomes do exist in other branches. And there are states of the Q numbers of the measure which also correspond to all of these other realities. And actually, I'm saying more than that, that it's not only that this is the right view, but we can even test. Test whether reality behaves this way.
- [36:35]
B
Excellent and great segue into moving into these portals or new experiments. And the first one is the measurement problem. I'm just going to read you a brief quote. Measurements are simply quantum entanglements between two physical systems, one of which can be thought of the system under observation and the other as the measurement apparatus. There is no division between observe and observer. They are arbitrary labels.
- [37:01]
C
Yes, and I think that's the key that I would put it this way, that every time you hear that there is a paradox in quantum mechanics, you can almost bet everything that this comes from assuming that there is a genuine classical observer somewhere in your account of the measurement. That's actually what I'm arguing, that it's a mistake, in fact, to assume that beyond some domain, let's say beyond a certain size of the system or the complexity of the system, it really goes back to a full classical behavior. So my view is that nothing, everything is actually quantum mechanical. It's just that for all practical purposes, for objects that are really, really large, it's unnecessary for us to take into account the full quantum mechanics. But that doesn't mean. Mean that the Q numbers are gone, that they're destroyed, that they've collapsed. It simply means that they are more hidden within other kind of behavior which is kind of stronger. So what I'm arguing in that first portal is that we really need to test whether measurement means what I'm advocating it means. And this is a very complex experiment. It's actually a variant of Schrodinger's cat, and I think many people would be familiar with that. So Schrodinger was also battling against this view that quantum world is weird, but it only applies to very small objects. And we are okay because we operate in the classical world and there is no connection between the two. So Schrodinger came up with this beautiful idea and said, listen, if I have an atomic event that's in two places at the same time, and in one of these places is it breaks a bottle with poison and There is a cat inside the laboratory at the same time in the other position. It just doesn't do anything. Nothing dramatic happens. Then Schrodinger said, if I take quantum mechanics seriously and apply it to everything, it simply would mean that this cat exists in both of these states. There's one branch in which it's alive, and there is another branch in which the cat is dead. And of course, this kind of experiment, even with a much simpler living system, would be extremely difficult to test. So what I'm advocating and what I think will happen in the first instance, is to do this with artificial intelligence, it seems. So what you really need is you need a system that's capable of answering a very basic question regarding whether they have made a measurement or not. That's all, I imagine, in that. So that's why I'm excluding animals, because it's very difficult to obviously communicate with animals and get a definitive statement from them. So I'm imagining some kind of artificial intelligence. Of course, if technologies really do progress, if neuroscience progresses, it might be possible one day to do this with a human observer. And that will be the ultimate, obviously, I think, for a physicist to test this at this level. So what I'm advocating is performing a measurement. So imagine instead of a cat, in this experiment, you have a quantum bit that's simultaneously in the state 0 and 1. This artificial intelligence system looks at this, which in my picture just means that it gets entangled to it. The Q numbers of this AI become entangled with the Q numbers of the quantum base. And what I'm now imagining is that there is a person who controls this experiment and who simply wants to verify whether the measure in this case has recorded a definitive outcome. And so, basically, in each of these branches, if you like, the measurer would see either a zero, a definitive state, zero, or one, a definitive one. Which means that the. They would simply confirm, if they're asked, what is it that you see now? Do you see a definitive state? They would say, yes, I now see a definitive outcome. So that would confirm that the measurement has been made. But what you need to do now, and that's the tricky bit, actually, that's the key. Maybe that's the surprise of this kind of experiment. You now need to confirm that both of these realities exist at the same time. They're really in a superposition. The state is actually entangled, as Schrodinger said, And that's the difficult part of the experiment. So I wanted to prove that it's not only that you see a definitive outcome. We know that you see definitive outcomes when you make measurements, but actually that that doesn't mean that anything has collapsed. It still means that the whole Q number based reality is still intact. And so the second part of the experiment somehow suggests that we should be able to interfere these two, to superpose these possibilities and get a different outcome to if really some collapse happens, some classical information really took place there and it's irreversible and so on. So I envisage that this would really teach us that you can almost have it both ways. As you indicated earlier that there is a fundamental randomness because the measurer cannot anticipate in advance whether they will see a 0 or a 1. But actually subsequently you can do do the second half of the experiment which proves that both of these took place at the same time. There is a measure in one branch of the quantum state who sees one outcome, another branch seeing another outcome. And actually you can prove that because you can do the second half of the experiment. And to me this would be a mind blowing experiment. And I think it would be a definitive proof that we can no longer hold on to these kind of interpretations, like Copenhagen interpretation, any related interpretation.
- [43:31]
B
That sounds fascinating. Before I move to this second experiment, I briefly want to ask you about this 1980 paper. You reference evolution without evolution, which suggests a block universe. That quote contains all possible things which can happen. How accurate is this paper towel? Things very much in line in sync with your thought process.
- [43:52]
C
Yeah, this is a beautiful paper. Actually these two former students of John Wheeler, of course, John Wheeler was in fact Feynman's supervisor as well. And I think he was an extremely creative physicist. And I think he was the first, first person together with maybe another German physicist, Weiziker, to really think that maybe quantum physics is suggesting to us that some kind of quantum information is at the foundation of reality. So what this page waters evolution without evolution picture. The way that I was attracted to that is precisely to do with the problem of how to merge gravity together with quantum mechanics. So if one theory is dynamic and it tells us that it's all about dynamics and novelty and new information and randomness. And the other theory, general relativity, is more like what I was saying Parmenides said, the static universe. Then I thought, could you somehow have both of these pictures accounted for in one formalism? And the formalism you just mentioned is I think the closest to that.
- [45:11]
B
Excellent. I want to move to the second second portal quantum experiments with time. And you note that the observation that different times are just like different realities in Space. And the key principle behind this is, quote, the coherent control of quantum information. What is that?
- [45:30]
C
This is another topic that I think is presented frequently in a very misleading way. Namely you would talk about relativity. And of course, as the name suggests, it says that many things that we think carry an absolute meaning, like space and time, measuring distances, measuring time durations, they are actually not absolute the way that Newton thought about it, but they are relative to the observer. So depending on how quickly you are moving, you will actually be recording different time durations and different spatial distances. Then people go on to say, that's why it's difficult to, to put together quantum mechanics and relativity, because quantum mechanics doesn't have that property. And in fact, exactly from what you said, I think it's the exact opposite of what many people say. The states in quantum mechanics are also relative to who writes these states. And so in this chapter I wanted to suggest experiments to test exactly this. So I think, I actually think that relativity benefits a great deal from the fact that quantum mechanics also says that the states that we write down are relative to where we are in this dynamical picture. And in fact, as the previous experiment that we were discussing shows, the measure who measured the qubit will either write one state of the qubit down or another. But the person outside of that box actually has to agree that these two possibilities are still superposed quantum mechanically. So that person will write yet another state to describe the whole thing. Each of these has a completely different perspective and they're all sitting together consistently. That's the beauty of quantum mechanics. There's no paradox there. So I thought, wouldn't it be fantastic to try to apply some of these things we've learned in quantum information? I'm going to describe it briefly now. So what I had in mind is to merge together the Einstein twin experiment, which is an experiment where two twins decide that one of them stays on Earth, the other one goes on a journey and comes back. And what we know from relativity is that the traveling twin is always younger. And if they travel further away and faster, they will be even younger. And of course, we've all seen this in various sci fi movies like Interstellar and many other ones that I can think of. So what I thought is, wouldn't it be interesting to test this with a single quantum object? So remember, in quantum mechanics you have this superposition. You don't need two physical objects. You can actually make a superposition of a single atom. And we have extremely accurate atomic clocks, in fact. So this would involve an already existing technology which we haven't put in a superposition yet. That's the challenging bit. But what I have in mind is take a single atom, for instance, put it in a superposition of two different places, and this is a standard trick in quantum information. And now in one of these places, take it on a journey to travel away way and bring it back. And now here is the stunning conclusion. And again, like I said, we've never tested this, but I think it ought to come out this way. If quantum mechanics is correct at this level, you now bring it back, you bring these two possibilities back to the same location, and suddenly you have the same physical system which is younger and older at the same time. You can already notice that our classical language, our grammar, is not even sufficient to describe. I can't even express myself properly here. What do you mean at the same time? If it's a superposition of two different times and it brings exactly back this idea of relativity, there is one time for the person who does the experiment, and it's completely outside of these two, then there is a superposition of this single system which literally shows one clock time and let's say less clock or more clock time, depending on which way you go. So it really shows you that even the question what time is it? According to this atomic clock? Doesn't make sense. Quantum mechanically, it's in a superposition, and if you were to measure it now, remember the first experiment, you would actually end up revealing both of these realities in different branches of their existence. So I thought this is really profoundly interesting. It's telling us something really profoundly interesting about time.
- [50:33]
B
Absolutely. And you do a nice job of quoting Wheeler at the end of the chapter quote, time is defined so that motion looks simple. I love that quote. It nails it. We need to move on. For the reader, I should say there is a fascinating discussion in this chapter on the relationship relationship between quantum physics and the second law of thermodynamics as it relates to entropy. I will let the reader buy the book and read that chapter. It's fantastic. I do want to move on to the third portal or experiment. Can we quantize gravity? And if so, how does the Bose Marletto withdraw you obviously experiment, help us do that.
- [51:07]
C
I think this, the portal that we just finished, in fact was like a gentleman introduction into this question, simply because gravity. Einstein thought of gravity as bending of space and time. So in this portal number two, I was playing these quantum experiments with time. But now really what I want to ask is what happens if we include the whole space Time into this picture. And this probably is the biggest open problem in physics at present. If you ask almost a random physicist, what is the biggest outstanding issue, I think it's really quantizing gravity. And again, as I said, many people would argue that we shouldn't even be doing that. We should maybe be classicalizing quantum mechanics and making it look more like gravity. So there are many roads to quantum gravity. So what I'm suggesting then, and this is an experiment that I think we are very close to being able to do, and that's again extremely exciting to me to communicate this fact. So I'm looking at two massive objects now, each of which is in a superposition. And so each behaves like a quantum bit. I have a quantum bit which is a mass in two different places physically, and another mass in two other different places. And the question now is that you want to really ask gravity the following question. Does the gravitational force act between each of these four locations simultaneously? So is gravity capable of acting through superpositions the same way as anything else that we are used to? Or would something more dramatic have to happen? Would some collapse of these superpositions occur and gravity would simply act in the old classical way, the way that Einstein and even Newton earlier imagined it? So this is what this experiment is trying to test at a very basic level. The surprise for many people, by the way, was that that you could test this with lab based experiments at low energy. Prior to us really writing these papers, Sugato Bosenchia Maletto and myself, prior to us writing this paper, most people would say the energies that you require to detect any quantum missing gravity are stupendous. We are orders of magnitude away. You need huge accelerators like CERN or like Fermilab, anything of that order of magnitude. However, what we thought is that you could in fact reveal this by again utilizing quantum information and applying it to a system with reasonably small objects that are potentially feasible to, to keep in a quantum mechanical state for long enough. So again, I'm betting personally the gravity will be quantum at that level. And that's hugely interesting because I think first, it would be a first piece of evidence to falsify Einstein's theory. So far, Einstein's general relativity has passed all tests, just like quantum mechanics in its own domain. It's as good as quantum mechanics is in the micro domain. And this would excitingly be the first piece of evidence telling us, no, it's not sufficient, it's not adequate in this regime. It would eliminate a host of possibilities. There are all sorts of Theories out there which are trying to combine classical gravity with quantum matter. And I think this would simply say it doesn't work. You cannot do that. It wouldn't be sufficient to tell us which quantum gravity road we should take. It would say, yes, gravity has certainly some quantum components, it can do these things. But ultimately really to come up with the full theory, we would have to then do follow up experiments. But that's exactly what this portal is about.
- [55:19]
B
Perfect. I do want to ask you a follow up question specifically around black holes and whether or not they would violate or contradict this idea of quantizing gravity.
- [55:29]
C
That's the key question at the other extreme, because this lab based test, the low energy extreme, is the one where you really get, get the weakest form of gravity, if you like. You are now asking about the strongest form of gravity. What happens if I had these massive objects which are ultimately condensed into black holes and as we know, nothing can, you know, even light cannot explain escape a black hole. So this is a big open question. And in fact at present it's not even clear how one would test. There is a school of thought suggesting that something irreversible will happen there and gravity will really collapse quantum superpositions. There is another school of thought which actually says that you can make a perfectly consistent quantum account of a black hole. So I would probably be leaning more towards that direction that even at the strong regime of gravity, I think we should be be able to reconcile the two theories. But what this does imply is that no information is ever fundamentally lost in the universe, even inside a black hole. So if you wait for long enough, this information could come out of a quantum black hole.
- [56:56]
B
Perfect. I want to move to the fourth portal, which I found the most fascinating, namely the relationship between life and being. Quantity. Want them? On the one hand, you conclude there are certain processes like photosynthesis which support quantum biology. But you do note life needs classical information. Can you reconcile those viewpoints?
- [57:15]
C
Again, it's a great question. This is another direction where I felt that when people discuss the meaning and possible limitations of quantum mechanics, then of course gravity is, is potentially the most likely culprit to change something. But there are many people who feel that quantum superpositions collapse when quantum systems encounter living systems. So some people even argue that life would find it difficult to operate only based on quantum information. Because you really should have as little uncertainty, if you like, like attached to your, let's say biological processes, observation, anything of that kind. And that's behind the quote that you mentioned that it seems that all life really ultimately processes classical information. And I think what I found, amazing, and these are again developments in the last decade or two decades, is that chemists and biologists have started to, to do experiments where they uncovered that many processes in biology are actually quantum mechanical. They are not large scale quantum computations of the kind that we would like to make, but they nevertheless are specialized quantum processes. So people who study photosynthesis, how plants absorb light and how they transfer it into chemical energy, energy, they have found that many of these energy transfers are genuinely taking place in a superposition. That this energy inside plants takes many routes at the same time, rather than kind of classically stochastically, randomly hopping between different possible locations in these complex molecules. And we have evidence in magnetoreception in many other areas of biology that actually quantum information and quantum physics seem to play a crucial role. So that's what I was exploring there. I was trying to almost turn this question on its head and say, rather than life requiring classical information, wouldn't it be amazing if the opposite was the case, in fact. And so not only is life more efficient if it evolves a certain quantum information processing abilities, but in fact, it could even be, you could even speculate that maybe the origin of life, that life even owes it to quantum mechanics, so that inanimate matter cannot really become alive in classical physics, that you really require something like quantum mechanics. So I think those are the kind of questions that I explore in that period portal.
- [60:18]
B
That is fascinating. I want to move to the fifth and final portal, namely detecting quantum ghosts. What are quantum ghosts? And how does local tomography solve the problem of entanglement in ghost modes?
- [60:30]
C
Great, that's a great question. Local tomography is a fantastic. It actually goes back to some of the papers written by Bill Wooters, whom we already mentioned in Evolution Without Evolution. Possibly one of the most creative, creative physicist that I've ever met myself, and I think so I wanted in that final chapter to go back to other bits of physics that I thought would make much more sense. So these are bits of physics where people by and large agree that they work well. We have a good theory to account. These are the bits of physics that don't involve gravity, but involve quantum mechanics. And people call this the standard mechanics model. And in fact it takes into account all other forces other than gravity. But what I wanted to say is that maybe we are now in a position to test even what we think is the best description of reality that we have at present. And one of the features I felt there are many Other, in fact, and you could probe many other things. But I think the one that stands out from me is this idea that there are certain degrees of freedom of the electromagnetic field. But I think the same ultimately applies for gravity, interestingly enough. But I wanted to focus on electrodynamics because that's already been quantized and I think we understand it much better. So there are certain degrees of freedom of the electromagnetic field which people say ought not to be treated quantum mechanically. And this is weird to me. So basically, why do they exist? You can say why do they even exist in the first place? They exist because of the compliance with relativity. So in relativity, everything we talk about, every property has to have four components, a little bit like three spatial dimensions and one temporal dimension. They're treated together like one vector. Vector. And every other property, if you think about the electric field, the magnetic field, anything else we discuss must be a four vector. Must be a vector with four components in order for relativity to be consistent, to be consistent with relativity in this case. Now, as it happens with light, with photons, the story as I mentioned, says two of these degrees of freedom, freedom give us photons and we can detect them. And they're beyond any doubt. But the other two degrees of freedom seem to need to exist logically because of relativity. But the story goes that we can never detect them. And that's why they're called ghosts. And so I wanted to challenge this. I just picked up this topic because I thought this sounds very weird. Theory is telling us that they must be there. The underlying underlying elements must be there for consistency. But then theory also seems to suggest to us that they can never be detected. And that's really weird. Why postulate these elements of reality if you really argue ultimately that they can never be detected? So I thought if we are consistent and we attribute Q numbers to ghosts as well, that's the idea again, to really take this Q number based reality seriously and describe everything they that we think matters quantum mechanically. Then actually with Chiara Maletto, I have a sequence of experiments through which we could detect the ghosts. And what you mentioned with local tomography is the following way. So what you are detecting, it's again a Schrodinger kind of experiment, but with this twist of local tomography. So we would take a charge like an electron, put it in a superposition position of two different locations, and if you treat ghosts quantum mechanically, they should actually be entangled to this electron, which means they are correlated. They are in a different state in one location and in yet another state in A different location. And the question is, can we test it? Do they really become entangled? Spookily. Interestingly, if you were not testing them in that state, but if you brought them back to the same location, this effect would be gone, which is why I think people traditionally call them ghosts. So we said, why don't we just keep the superposition, make measurements on one of these locations on another location. And then people like Bill Waters have taught us that we can actually reconstruct the whole quantum mechanical state. And the name tomography is simply the state reconstruction of this electron. Electron. And this state reconstruction would tell us whether the electron is entangled to the underlying ghosts or not. And if it is entangled, then obviously these ghosts make a difference, and that's the easiest way to detect them. And I think this experiment is also within our reach. And I felt that it would actually transform the way we understand quantum field theory and the Standard Model.
- [65:52]
B
Excellent. Last question. Question. You suggest the Christian concept of via negativa can help us define the new physics. What is this concept and how does it relate to constructor theory, which state that all laws of physics should ultimately be phrased in terms of principles that tell us what tasks can and cannot be performed in our universe?
- [66:12]
C
Yes, I think this is an excellent question. In my book, I felt that one thing is, of course, to discuss the portals which I feel could lead us to a new reality.
- [66:25]
B
Reality.
- [66:26]
C
But I felt that it wouldn't be honest, really, and it probably wouldn't be interesting if I didn't also try to anticipate what kind of road should we be taking. What is this telling us? What kind of new theory of physics could emerge and how should we approach that? With what methodology? So, and this goes back to David Deutsch, my colleague David Deutsch, the person who invented quantum computers as well. And I think Yara Maletto developed most of this theory in her thesis and applied it to various aspects. I think this is an approach that reflects Einstein's thinking. Einstein was a person who loved using principles to actually derive profound conclusions from that. So even if you look at relativity, he simply realized, and this was a stunning discovery, that if you simply acknowledge that motion at a constant speed can never be detected, so you can never tell whether you are stationary. All the laws of physics are the same for someone who is standing still and someone who is moving at a constant velocity. Velocity. And the second postulate being the speed of light, that nothing travels faster than the speed of light. He saw automatically that relativity comes out of that. So here are Two very easy principles to state. Anyone can understand what these two principles mean, but in fact, they lead us to some profound physics. You can even argue what dynamics should look like based on these kind of principles. And I think David, David Deutsch was motivated and inspired by this kind of thinking, and he felt that maybe we could go even deeper as far as the whole of physics, not just relativity, but maybe we could cast a whole of physics in terms of just the fundamental principles. So I should say that's in contrast how we currently understand it, the way we currently understand it. It is you give me the state of your system, specify the initial state of your system, let's say the location of your system, and then tell me the energy of the system. We call that the Hamiltonian in quantum mechanics. And once you give me these two, I can compute what's going to happen to the system at any future instance in time. So basically, you specify the full dynamics, give me the initial state, the initial condition, tell me how it evolves through this Hamiltonian. And that's all of physics basically is done this way. And so David felt that maybe it would be more productive to have a bunch of principles constraining us as to what can and what cannot happen. So inspired by relativity of Einstein, Einstein himself, by the way, was inspired by thermodynamics. The laws of thermodynamics are also principles. The first law being the energy conservation. It says whatever you do, whatever dynamics you have, energy always stays the same. And the second one is this famous second law of thermodynamics that you mentioned, which says that the disorder is always going to be increasing with time in a closed system, again, no matter what kind of stuff you do to that system. So David thought, why not expand this to the whole of physics? Wouldn't it be interesting thing if all I need to specify to you is the transformations that are possible or even the complement, the impossible. If I just simply rule out what cannot happen in this universe, what kind of transformations cannot take place in this universe, then what I'm left with is basically the totality of physics. Whatever is possible, whatever remains is what's possible. And it seems to me this is a beautiful, a beautiful guide. It's completely unexplored. And in my book, I speculate a little bit how I think we could take this further. So this kind of transformation might be what's required ultimately, even to unify quantum physics and general relativity. So even if the experiments go the way that I think they would go, we're still going to be asking the question of so how do we put these things together? What is the right way to do that? And I felt that that constructive theory is certainly one possible approach.
- [71:09]
B
Excellent. That concludes our interview. The book is Portals to a New five Pathways to the Future of Physics by Vladko Bedraul. I should note Professor Bedraw is a wonderful substack called Musings on Quantum Mechanics which covers these themes in more detail, as does the book, obviously. Vladko, thank you so much for your time in writing such a fascinating and thought provoking book. It really was mind expanding.
- [71:33]
C
The Flesh is online. Thank you, Greg.