The Physicist Who Puts Penrose’s Quantum Ideas To The Test – Ivette Fuentes (Transcript)

And then after a while, I missed the rigor of mathematics. I felt like it was too much freedom to come up with ideas and not being able to ground them on that beautiful mathematics that I had learned.

And I decided to come back to physics. But then the first class I signed up for without knowing really what it was, was called modern physics. And it was quantum mechanics and general relativity. And that’s when the whole passion, it was just so exciting. And I became sort of in love with both.

The Tension Between Quantum Mechanics and General Relativity

HANS BUSSTRA: That’s so interesting to hear from you that you have not had this sort of more classical route. Because you must have excelled at math in high school, right?

And I don’t want to stretch the dancing metaphor too far in this conversation, but I did a video about relational quantum mechanics in which I remember I had this, I used it sort of just as a visual metaphor, sort of this Einsteinian theater of space-time where we had sort of a script, the math to give us, okay, where you sit in the theater might give you sort of a different take on what’s happening on stage, right?

But we can all sort of account for it if we take this outside look and see, oh, you were sitting there. So of course that actor was moving right. Oh, you were sitting there, he’s moving left. So that’s just general relativity.

But then of course, with quantum mechanics, all of a sudden a lot of crazy questions pop up. What is the stage where the actors? I mean, what’s an observer, right? What’s a measurement? Is there even still a script to account for all of that?

My question to you is to sort of also set the stage for this conversation. Can you sort of point to that incompatibility or that tension between quantum mechanics and general relativity? In simple terms, where do you see the big tension?

IVETTE FUENTES: Well, I guess underpinning the incompatibilities is that in quantum mechanics, as in classical physics, time is absolute. The transformations are Galilean transformations. So that’s what we learn in high school. When we want to describe, let’s say, physics from the point of view of an observer in a bus as compared to an observer in the street, then we have Galilean transformations.

And one key thing about it is that time is absolute, which means the time from the perspective of the observer in the bus is, well, the clock ticks at the same rate as an observer in the street, or actually any observer moving at constant velocity, even if the velocity is very high. And then we have velocities add up and so on. So if you remember from your high school, those transformations we used with Newton’s laws and so on.

But then if you go to general relativity and special relativity as well, we have different transformations. And that’s because Einstein postulates that the speed of light is constant. So when you try to then derive the new transformations, well, they’re different. And then time is no longer absolute, but it’s relative.

And you get this kind of funny thing that mathematically, the positions and the time transformations mix space and time, which is very counterintuitive and that gives rise to relativity. But those are Lorentz transformations. So they’re very different from Galilean transformations.

So quantum mechanics has the same transformations as classical physics, Galilean transformations, whereas general relativity and special relativity, they’re underpinned by Lorentz transformations. And that is a big incompatibility.

The Historical Quest for Unification

HANS BUSSTRA: Can you sketch sort of historically, just like a brief bird’s eye perspective, we don’t need to go in depth on the different theories, but how historically, ever since quantum theory, we’ve tried to unite them. So that would be like quantum field theory, I think came first and then we ended up with string theory. But if you can sketch that sort of landscape and where you came in.

IVETTE FUENTES: Yes, well, I guess from the onset there were, in the beginning of the 1900s there started to develop the two theories, on one hand quantum mechanics, and on the other hand general relativity. And I guess it became quite obvious that there would have to be some scales, and we can talk maybe about the scales later, at which the two theories would have to interplay.

And I guess it must have become early on the problem that it was not possible. And also first some of the attempts involved just taking Einstein’s equations and trying to turn the matrices into operators and things like that. So trying to combine the mathematical formalism of quantum mechanics where we use operators that don’t commute. And then, well, general relativity uses differential geometry and tensors and things like that.

So how do you combine these mathematical structures to create a new theory? And that maybe looked easy at the beginning and very soon after people started to see that was highly non-trivial. And after almost 100 years it’s not been possible to do that.

And then from there there’s been other approaches like string theory and loop quantum gravity. Lee has been a big figure in loop quantum gravity. And when I was a student those were sort of the options. And I was always interested in fundamental questions. Actually, even from childhood I was interested in, I wasn’t aware that I was asking some fundamental questions, but we can go back to that maybe later.

But as a student I was interested in what’s time? And I noticed that, look, I can calculate with it, but I’m not really understanding at a fundamental level what is it exactly, and that kind of questions. But I did get interested in theoretical physics, but all my friends and colleagues and so on were going to string theory.

And when I learned about string theory, I loved the idea. I thought, oh, this is so beautiful that from one string you can get from their different vibrations the different particles and so on. But when I went more into it and that it gets all these dimensions and it gets so complicated, I felt…

HANS BUSSTRA: Those are a lot, right. For people who are not familiar with string theory. So you don’t say it’s a field, but there’s strings from which particles, I mean, excitations of strings, I think.

IVETTE FUENTES: Yeah. But I know very little about it because…

HANS BUSSTRA: You end up with, like, in some versions of string theory, at least 10 or 11 dimensions, which is just completely crazy to just fathom for people who are not into mathematics. But that’s it. You end up with crazy amounts of many dimensions.

IVETTE FUENTES: Yes. And so that felt to me, like I said, it reminded me a bit of the epicycles that were needed to describe the trajectory of planets. You know, people in the past wanted to describe the trajectory of planets. And the idea was that, well, the circle is a perfect figure, but because of that, nature had to follow circles always.

And you cannot describe the trajectory of a planet using a circle. So then they were like, well, why not a circle within a circle? That works a little bit better. But still very far away. Well, why don’t we add another circle and another circle? So you needed, I think, around 600 circles within circles in order to explain the trajectory of a planet. And then came Kepler and said, well, it’s an ellipse.

HANS BUSSTRA: And then you’re back to one shape.

# Quantum Optics and the Path to Perimeter Institute

IVETTE FUENTES: Yeah. I mean, I want to be respectful, of course, because I think it’s been great to have that effort of following string theory. And who knows, maybe one day they find that they’ve done the right thing. But for me, at the time, as a student, it felt like the wrong thing to do.

So instead of doing that, I went to quantum optics and so on, because at the moment, I heard about some really exciting experiments that were just taking place. And I heard, oh, somebody demonstrated teleportation. That was like an entanglement. That was Anton Zeilinger that now got the Nobel Prize quite recently for his experiments with entanglement. And the Wineland had, like, trapped ions in a trap. So, like single particle quantum mechanics.

And Serge Haroche was doing cavities with atoms inside, also testing the foundations of quantum. Before that, you had experiments that had many particles. So it was very hard to say we’re really testing principles of quantum mechanics. But these experiments were kind of very clearly new. And I thought, they’re going to open up a deeper understanding of quantum mechanics.

My teacher at the time was always saying, like, well, you know, we can’t do experiments with a few particles. So quantum mechanics just talks about ensembles or quantum mechanics just talks about statistics and so on. And I thought well, maybe these experiments tell us something more fundamental. So I got very excited about that. And that’s how I decided to study quantum optics. Because I think I like ultimately what I wanted to understand, but I didn’t have it very conscious. What’s reality made of?

HANS BUSSTRA: Yeah, like truly metaphysics.

IVETTE FUENTES: But yeah, but I think I digressed like really long because you were asking me about what happened at Perimeter.

HANS BUSSTRA: Yeah.

IVETTE FUENTES: So I arrived there with the idea of continuing my work in quantum optics and entanglement and Berry phase. I was also working on geometric phases and I found all the other people like the other postdocs working on gravity and I became very jealous.

HANS BUSSTRA: Gravity pulled you? Yeah, you felt the pull of gravity.

The Attraction to Gravity

IVETTE FUENTES: That is such a beautiful scene. Theory and… Well, I had done a thesis in astrophysics as an undergraduate. My first paper is on super galaxies. Then I moved and I started to work on quantum optics and entanglement. I had started to do some work on holonomic quantum computation. So I had already kind of moved quite a bit.

And then I thought okay, if I now jump into like general relativity or something like this, which is what I was attracted to, maybe that’s a little bit too much. And I went to a talk about quantum field theory in curved space time. And they wrote on the slides they had like what we call in quantum optics a two mode squeeze state. So a special type of state of light. And I recognized it and I asked like oh, that’s a two mode squeeze state, isn’t it? And they said it was not a familiar language for them.

And that’s where I realized that I had learned during my Ph.D. all these tools like calculating entanglement and so on that I could just apply now to quantum field theory and curved space time.

HANS BUSSTRA: That’s interesting. So then it became first became clear to you that sort of this whole path of jumping or dancing between these different fields now became very valuable.

IVETTE FUENTES: Yes.

Understanding Quantum Field Theory in Curved Space Time

HANS BUSSTRA: In this new field. But to understand quantum field theory in curved space time. Let me, I’ll probably explain it completely wrong, but correct me please. I’d say that is something like quantum usually treats like very small systems particle level. And we don’t have, we assume that gravitational effects don’t play any role because it’s just too small. Is it that quantum field theory in curved space time is that sort of the study or doing experiments in quantum where gravity does play a role. Is that it?

IVETTE FUENTES: I think that the main idea of quantum field theory in curved space time was to take steps towards the unification of quantum mechanics and general relativity.

HANS BUSSTRA: Yeah.

IVETTE FUENTES: And it’s like intermediate step or like a semi classical theory because what it does, it considers… It’s like these words of classical. And I maybe clarify that because we use it in a different way. So if we’re talking about quantum mechanics…

HANS BUSSTRA: Yeah.

IVETTE FUENTES: We would say classical physics thinking Newtonian physics. And then quantum physics is not classical in that sense. But then we also have general relativity being different from classical physics being Newtonian. Okay. So there’s like this distinction.

So in quantum field theory, the space time is classical in the sense that it’s not quantized, but it’s like given by Einstein equation. So you think you have a mass distribution. So it could be, let’s say the sun and the sun curves the space time. And then you think about how would fields like… It could be the electromagnetic field, so light would behave in the space time, let’s say of the sun or some curved space.

HANS BUSSTRA: Yeah.

IVETTE FUENTES: So it’s not quantum gravity because it’s not studying how the fields themselves curve space time, which we call like back reaction. So it’s more like the quantumness. No, it’s like this attempt of bringing quantumness with relativity.

HANS BUSSTRA: Yeah.

IVETTE FUENTES: So the relativity part is the underlying space time that is given by a source and that obeys Einstein equations for general relativity. And on top of that you put quantum fields that obviously behave quantum mechanics.

HANS BUSSTRA: To help people understand. Because this might be… I think I understand, but it might still be quite abstract for people just… Yeah, sorry. I think the dance metaphor does help here. If you were standing on these two legs with quantum. And the community is sort of… You have… Everyone is sort of leaning a bit more on one or the other. Is it that with quantum fields theory in curved space you’re leaning a little bit more on relativity? You’re saying. Okay, a little bit more. We take that sort of as fundamental sort of spacetime and then we bring in quantum field theory. And because this also relates to Roger Penrose’s position, who says that we need to sort of gravitize quantum.

IVETTE FUENTES: Oh yeah, we go, we go into…

HANS BUSSTRA: You see what I’m hinting at.

IVETTE FUENTES: But I would say quantum field theory in curved space time is to have like one foot in each side solid.

HANS BUSSTRA: Okay.

The Question of Massive Systems in Superposition

IVETTE FUENTES: But it is not the full theory because it does not consider how the quantum fields curve the space time itself. So, for example, now, going into, like, Roger and so on. From my perspective, one of the most interesting questions that we need to consider at the moment in this interplay of quantum mechanics and general relativity is if you have a massive system, like, could be people already do this in the lab.

Trap little silica beads that maybe have, like, 10 to the 18 atoms, something like this. If you can take a system like this and put it in a superposition in space, like, in two different locations. Is that, like, a stable situation or not?

Now, that would be in a way, like an aspect of quantum gravity. Because you have a mass. And you believe general relativity. The mass curves the space time. So now, if you have a mass in different places, that’s having, like, a superposition of space time configurations. And we don’t know if that is a stable thing. I mean, we know we can do that. Because you can do it with atoms.

HANS BUSSTRA: Yeah.

IVETTE FUENTES: And, well, the only thing that happens is that atoms have, like, a negligible sort of curvature. Let’s say it’s very, very small. But they do have one. And we know we can put atoms in a superposition in the lab. People have done that many times. Actually, Marcus Arndt at the University of Vienna has the record for superpositions with mass. He can put a molecule. And the molecule has around 2,000 atoms in a superposition. So that’s the record.

But that is already the full thing. Because you’re looking at how the system itself, in this case, let’s say the molecule is in a superposition. At the same time it has its gravitational field.

HANS BUSSTRA: Yeah.

IVETTE FUENTES: So the gravitational field is in a superposition as well. So there are, like, questions about can gravity be in quantum states in that sense. Because gravity is different than other forces in the sense that it has an equivalence principle. So we can talk about that in more detail as well.

Because it’s important that question of can we have a massive system in a superposition? Is that a stable situation or not? This is the key to understanding the interface between quantum mechanics and general relativity. In my opinion. The experiments are going there. So that’s another interesting thing to talk about.

But quantum field theory in curved space time cannot address that simple question. Because it’s assuming that the system that in that case is not particles, it’s a field, is not curving the space time itself. So in that sense, it’s an incomplete theory. But when I discovered it, that was at the Perimeter Institute. I loved it because I felt that it enabled you to take already some really interesting things. Steps.

So I also had like the experience from quantum optics that when I was studying quantum optics from my textbook and I saw also the history of quantum optics, there was like a stage where there was also a semi classical theory. So let me elaborate on it a little bit on that.

HANS BUSSTRA: But… Oh no, I think maybe, maybe. Yeah, I’d love to hear. But maybe just, just a couple steps back for just and myself also and people watching to understand the dissatisfaction for instance someone like Roger Penrose has with quantum theory that is incomplete. And from there on he sort of pursues of this objective collapse which in my opinion is a way to sort of try and make it, to bring it sort of a bit more back to an Einsteinian worldview. Is that a way to put it if I would ask the question like that?

Penrose’s Perspective on Quantum Mechanics

IVETTE FUENTES: Well, Roger thinks that the principles of general relativity are more fundamental and that quantum mechanics has to change in order to, for us to unify the two theories. And the reason why is that there’s a measurement problem in quantum mechanics is already problematic. So if you think okay, we have a theory here that seems to be… It’s also not… It’s problematic as well. Right.

HANS BUSSTRA: We’ve been treating it now as if it’s not a problem, but it is in itself already. Exactly.

IVETTE FUENTES: It’s a huge problem. That’s why I think Roger would agree that both have to be modified. But if you gave him a choice which one do you think should one or the other. He would definitely 100% say we keep general relativity and we modify quantum mechanics.

HANS BUSSTRA: Because a lot of people… That’s his dissatisfaction with the theory. And it has to do with also with Einstein’s concern that you sort of… You just… It’s not, it’s indeterminate. We don’t know what a measurement exactly is. And that’s interesting. I think that brings us back to you where you were now going with.

And hopefully we can also touch on your work with Bose Einstein condensates here is that it still feels safe as long as we can just say quantum effects just rule out on a macroscopic level and there it’s no problem. And then we only have like philosophical problem. And that those are the Wigner friend scenarios. Like crazy scenarios. Like an observer in a superposition with a system isolated for next yet another observer to whom that observer with his system is in a superposition. The crazy stuff.

We’ve been covering that on our channel. I find it super fascinating philosophically. But usually physicists say that is not a problem in the lab, it’s not a real problem. But if your work, if that keeps going on. So we’re now at 10 to the 18 atoms, you said, but not like so. But that just clear. I’m just curious there too, because we are now bringing larger systems into a superposition. How far can we go on doing that?

Testing Gravity’s Role in Quantum Collapse

IVETTE FUENTES: Well, that’s what we want to know, right? So if, let’s say if gravity is not playing a role in collapsing the superposition, then it’s just like an engineering problem and we should in principle, keep going. So let me give you like a beautiful example of that and bring it back to Anton Zeilinger, that people started using photons and putting photons in a superposition or entangling photons as well.

The experiment started and that’s when I was a PhD student on tabletop experiments. So something that would fit in here. And then Anton went from there into saying, well, could we do this in Vienna between two labs? And that worked. Then he said, okay, two islands in the Canary Islands. So 2011 he did that beautiful experiment. Then from then he went to space with satellites and they can now distribute entanglement across thousands of kilometers.

And as far as I know, he’s thinking, he has some papers on quasars. Right. So the question is, well, you also mentioned quantum mechanics applies for small systems at small scales. But his experiments along with, he’s not the only person like a whole community. Paolo Villoresi, Rupert Ursin, I mean, there’s many people working on that. They can show that there are these, you can, like the quantum states are not that fragile as we thought they would, and that you can keep entanglement at those super long scales and keep going.

Now, with mass, the question is, can we do the same? So if what, you know, I should also mention that Lajos Diósi came up with this idea that gravity collapses the wave function independently from Roger, actually a couple of years before. But they both had this idea kind of from different, like different starting points and they came to the same idea. But we always remember Roger. So I like to mention.

HANS BUSSTRA: Diósi-Penrose conjecture. Yeah.

IVETTE FUENTES: Yes, yes. So if they’re right and gravity plays like a role and collapses the wave function, then that explains why we don’t see quantum superpositions in classical scales where you and I live. Right. So that’s why I like it because I think it explains kind of it would give a very nice explanation on how do we have quantum physics with particles with not much mass, but when we become massive, because photons don’t have mass.

So we know that photons can be entangled across thousands of kilometers. But in principle, if gravity does not have an effect on the superpositions, we should be able to put more and more and more mass and keep going. It’s just like a matter of engineering, of improving our technologies to be able to do these quantum experiments. Which is exactly what you see with Anton Zeilinger’s experiments.

HANS BUSSTRA: Cooling it down, isolating. But in principle, we could bring you or me in a superposition.

The Mass Limit Question

IVETTE FUENTES: Yes. So I think rather not. I think gravity affects. But that’s the main thing. So then you have Markus Arndt, for example, also in Vienna as well, Markus Aspelmeyer, even at my university, Hendrik Ulbricht. Then there’s people all over the world working with massive systems and trying to put them in superpositions. And technically it’s very difficult.

But if it’s not a fundamental thing that the state collapse, they will find a way to make the, we see how we advance with technology. Somebody comes up with a good idea, and if it’s not fundamental, then you can keep going. So then in principle, experiments would start also having more and more and more mass.

However, if gravity collapses, the wave function, then, well, more or less. If the current, let’s say, if you take Roger’s and Diósi’s formula as what gives you the time scale and the mass scales, that would be like masses of around four times ten to the nine atoms. Yeah, let’s say.

HANS BUSSTRA: And for people to understand roughly, because what are we talking about? At what level are we then?

IVETTE FUENTES: Well, it’s like, I think it’s like around a little, a small dust speck or something like that. But, well, in the, in the lab there, these small.

HANS BUSSTRA: But still, I mean, it’s still in a sense big, because that would be like microscopic, like, would be within sort of visual.

IVETTE FUENTES: So, so there are these little beads that Markus Aspelmeyer and Rupert, like, and, sorry, and Hendrik Ulbricht, for example, have in the lab. So there are these tiny silica beads and they’re, yes, they’re big for quantum mechanics and they’re like small for our scales.

HANS BUSSTRA: But according to Penrose and Diósi, that is the limit.

IVETTE FUENTES: Yes, according to their formula, that’s the limit.

HANS BUSSTRA: You are testing that?

Developing a New Approach

IVETTE FUENTES: Well, I’m like, I’m a theoretician. I’ve been sometimes I, experimental is, no, no, no, no. I’m a theoretician. I’m a theoretician. But you and your group, who loves to propose experiments. And I work with experimentalists, with Chris Westbrook who’s in Paris, and Philippe Bouyer who’s in Amsterdam. So they are like excellent experimentalists. And we have a project together.

And yeah, the idea is to test that. Only that I have somehow taken, let’s say the idea from Diósi and Penrose about the collapse. But I’ve kind of now taken my own take at it and route and it’s been a little bit like, let’s say, how do I say, like changing. I see Roger as my teacher, my inspiration, you know, like it’s like, what is like a word for that? I don’t know when you have someone who’s been your mentor or something like this. Right.

But you want that the student at some point becomes independent and does its own thing. And yeah, I will come up with my own take at the Diósi-Penrose conjecture soon. And I just steer it and change it.

HANS BUSSTRA: And can you give us a sort of, can you lift the tip of the iceberg? Can you sort of just give us.

IVETTE FUENTES: What am I doing?

HANS BUSSTRA: Yeah, what your difference, your different take is your, because it seems like you’re proposing your own collapse theory then.

IVETTE FUENTES: Yes. So Roger just gave like the formula and how you understand the formula is saying you have your particles, you have a mass, and then you take like a copy of it and then you calculate the energy that you need to sort of separate it to a distance B. So that’s called the gravitational self energy of the difference.

So Roger sort of gave us a formula for that. And then via an uncertainty principle with energy and time, he gets like a timescale from that. But this is roughly speaking, because that sort of the energy uncertainty principle holds when you have unitary evolution.

HANS BUSSTRA: Yeah, just one little pause that also to help me understand. So it would be a system in superposition that has now a gravitational, self gravitational influence upon itself.

IVETTE FUENTES: Yes, self gravity.

HANS BUSSTRA: It’s different than entanglement. We’re not talking about sort of classical entanglement where people think about faster than light communication, which is not the case. But I mean that’s what people know. Ah, it’s entanglement. No, this is not entanglement. This is superposition. And whereas the system now has a sort of self gravitational effect.

IVETTE FUENTES: Yes. It’s one particle in two distinct locations in space, left and right. And then you’re thinking there’s a gravitational.

HANS BUSSTRA: Aspect to that and super naive. Does it want to go back to itself? Is that a stupid question or.

The Collapse Mechanism

IVETTE FUENTES: Well, I mean, what Roger says is that it’s not that it goes back to itself, it just goes either left or right because of gravity. So that’s the main thing. Then Diósi took a step forward from there because Roger just, just gave us this sort of energy and then a timescale associated to it. But Diósi did more than that. And he wrote an equation sort of that gives you the details of how the system behaves and how eventually you get a collapse.

And it’s like a stochastic equation. So the system is in a superposition and due to gravity, it suddenly goes either left or right. But because it’s stochastic, it predicts some radiation. It’s not energy conserving and it predicts a radiation. And that was a point of that Roger and Diósi did not agree because Roger was saying, well, if it doesn’t conserve energy, there’s a problem with that model.

But then there’s been an experiment underground where they take a big mass and they look for the radiation. So there is not like a proper superposition. I think it’s just the prediction is that a mass like the one they have should emit radiation due to Diósi’s model and at least to the masses and the experimental parameters involved and so on, they didn’t see the radiation. We would say the model is ruled out up to those scales.

However, they could do more experiments at different scales and maybe find the effect at other scales. That’s the other thing I wanted to say is that the uncertainty principle tells you energy, uncertainty in the energy, you have an error in the energy times an uncertainty in time. And if it’s minimum, you have that, that’s equal to H bar over two. So that you can from there, from that simple equation, guess what is the time scale. So that’s what Roger did.

But that uncertainty principle holds when you do not have superposition. So if the system is going to decay, strictly speaking, that uncertainty principle does not hold. Also, that was an observation. And say, okay, it’s a good idea, it gives you a good starting point. But one could refine it and one could do this with a bit more detail, let’s say, to get the right timescale. That’s when I’m telling you these timescales that you need four times ten to the nine atoms in a mass in order to test if this is true, is using that timescale. We’re going to come up with a refinement of that soon.

HANS BUSSTRA: Yeah.

IVETTE FUENTES: So that might sort of change. So that also gives room to say, well, not because of our model, but in any model, you always have some parameters that you can modify so you can rule out an experiment up to some place, let’s say some mass. But that doesn’t mean it’s completely ruled out because you could always find another scale at which still the effect could occur.

But at least to the masses that Roger had predicted that you would see some collapse, they didn’t see evidence of the model that Diósi constructed. And I think that’s when I got interested in it because Roger was kind of a little bit like, oh, there is a saying that I’ve been disproved, but it was not even my model. And then things like that. Yeah, yeah, yeah, yeah.

And, and then I thought, okay, maybe with everything I’ve learned so far, because I was always working with at the interface of quantum stuff and relativistic and so on. Well, this is all Newtonian. But gravity, no, maybe I can do something. And, and that’s.

HANS BUSSTRA: Yeah, okay. So I think this is super nice stuff for like our physics audience who will enjoy this. We can also put, we will put links, links below to papers and stuff for you to dive in. But like one step back or just more bird’s eye view, because these are refinements within sort of the, what I see is sort of the same pursuit, namely to see if gravity collapses.

Where are we now experimentally? Where are you? What can you say about that sort of in your experimental work? And nice to touch upon those Bose-Einstein condensate. So these are pretty large systems that are relatively easy to bring into superposition. Is that.

A New Experimental Approach

IVETTE FUENTES: Well, let me tell you maybe a little bit, because also that’s like a big departure of what people are doing. So maybe I can like tell you a little bit about that. So most of the experiments taking place to test gravitational, let’s say induced collapse involve solids. So there would be like the molecules of Markus Arndt, the beads that, you know, I mentioned. There’s also like people working with little rods or membrane mirrors, cantilevers.

But in these cases the atoms are always bounded. And then you have to prepare the state left, like the bead on the left or the system and the right. And I was asking Roger what’s been like the problem on testing, you know, the gravitational induced collapse. And he was saying like, well, the temperature that, what the experimentalists are saying is that the temperatures are too high to see the effect. So I checked, and Markus Arndt’s, for example, temperatures are in the millikelvin scales. And then I was thinking, well, Bose-Einstein condensates are very cold.

HANS BUSSTRA: Just briefly, what are they.

IVETTE FUENTES: Yeah, I’m going to explain what they are. Yes, yes.

HANS BUSSTRA: Okay, we’re getting.

IVETTE FUENTES: They’re like, like explaining what they are. I love them.

HANS BUSSTRA: They’re just like such a beautiful, very deep. And we have to explain basics. So it’s, it’s back and forth between.

IVETTE FUENTES: Going deep and the basics.

HANS BUSSTRA: But I love that.

IVETTE FUENTES: No, but it’s such a beautiful system that it’s just like a pleasure to talk about it, Bose-Einstein condensate.

HANS BUSSTRA: There we go.

Quantum Behavior and Superposition

IVETTE FUENTES: Okay, so in the undergraduate, when you learn quantum mechanics, I think it’s the first or second example that you see of quantum behavior is that you consider a particle, an atom or something like this in a well potential. So the well potential could be made by electromagnetic fields or something like this. But the point is that the atom is trapped in the potential.

So if you cool down the atom, so you take its kinetic energy and so on, it starts going down to the lower energy levels of that potential. And when it reaches the ground state of the potential, the atom becomes completely delocalized within the potential. So we’ve been talking about a superposition of an atom left or right? No, but in the potential. The atom is not left or right inside the potential, but it’s everywhere, delocalized.

HANS BUSSTRA: This is a good way to understand like super basic quantum mechanics. Just cool down. Cool down. Ground state it is then in a superposition.

IVETTE FUENTES: Yes, but of everywhere. It’s like completely delocalized. No, I find that very beautiful and utterly, utterly strange.

HANS BUSSTRA: Yeah, exactly.

IVETTE FUENTES: But that’s, I think, why I’ve loved quantum mechanics. When you were asking me about what brought in this passion in physics was like, when I find something that is counterintuitive, I love it because it makes you think deeper.

Bose-Einstein Condensates

Now put the 10 to the 5 atoms and cool them down to the ground state. That’s a typical experiment has like 100,000 or a million, commonly rubidium atoms. But people also use sodium and other atoms to cool them down to a Bose-Einstein condensate. So atoms are what we call bosons. So bosons can occupy the same sort of energy states to differentiate them from fermions that don’t like to be together. And then they push each other away and then they have to occupy different levels like bosons.

That’s why I like working with them. They’re more cozy, they’re friendly, they all like to be together. So they can all occupy, let’s say, the ground state. If you had them all occupying the ground state, the temperature would be zero temperature. But that’s like, you can’t have zero temperature. Impossible.

Atoms interact so they either collide or there are other forces between them. And what that does is that they cannot occupy all of them like the ground state. And they create this system in which I like to think about all the atoms in the ground state. We call it the bulk of the BEC, like if it was an ocean. And then the little interactions give rise to little waves that live on the condensate that are quantum waves and those we call like the phonons.

So it’s a really beautiful system. And I’ve been working with this system for a long time on how can we use it to test a bunch of gravitational effects like dark energy. Searches for dark energy, for dark matter, for modifications of gravity, all kinds of things. Because these phonons are very sensitive to sort of space time changes.

HANS BUSSTRA: Now we’re back at that where we were earlier, that spacetime curvature then, right?

IVETTE FUENTES: Yes.

HANS BUSSTRA: What are the gravitational effects you are seeing on these phonons? Can we measure that?

Detecting Gravitational Waves with Quantum Systems

IVETTE FUENTES: Well, it’s all theoretical right now. We haven’t done experiments in that direction yet. But what kind of things we would see is that if you have like a high frequency gravitational wave produced by for example, it has to be persistent and monochromatic. So for example, pulsars sometimes can have like bumps or things like that. Well, that’s like the astrophysics.

Coming back to astrophysics is nice because in my career I’ve danced around, but I come sometimes back to where I started. So I love it when that happens. So you have some objects in astrophysics that have some sort of bumps or something like this. So when they rotate, they create space time perturbations that are very long lived, let’s say.

Such a thing would change the states of the phonons in the Bose-Einstein condensate. You have to prepare a very sensitive state of the phonons which are called squeeze states. But still it’s like an antenna in a way, but a quantum one. And then the change in the space time would change the state of these quantum excitations. And if you can detect those changes, then you could detect like a high frequency gravitational wave or something like that.

So yeah, I started proposing these things a few years ago now, like 10 years ago. And well, that was also kind of, it was, I mean, you know, the way to detect gravitational waves is using huge apparatus, right. LIGO and the interferometers, the light interferometers, lasers, interferometers are humongous. The arms are 3 kilometers and stuff like this.

And then like 10 years ago I was like, oh, I think you can detect gravitational waves of other frequencies. It’s not in competition with those frequencies from LIGO and so on. But I had high frequencies this with the Bose-Einstein condensate that it’s coming back to a tabletop experiment because a Bose-Einstein condensate you can produce in a small lab that would fit in this room. Well, by far. You could have actually many experiments like that in this room. So that’s quite a bold idea to say you can detect gravitational with such a small thing.

HANS BUSSTRA: But experimentally that would also be a breakthrough in the sense that you can now work with it with much smaller setups, etc. So if I understand you correctly, yes, no.

IVETTE FUENTES: And when I came up with the idea, of course part of the community came up and said, you’re nuts, right, you’ve lost it. But many people, or I wouldn’t say many, but some people now are coming up with similar proposals. And you know, at the moment I’m working with Chris Foot at the University of Oxford who’s trying to produce the squeezing that I propose that is needed in order to move forward in that direction.

And you need a big BEC. So he said, okay, I’m interested in taking like a large BEC and trying to see if we can produce the squeeze states that are required. So it’s moving forward. But it did take quite a lot of trust in what I was doing on the rigor of what I was proposing with like the mathematics, because I’m a theoretician and also I’m always in contact with experimentalists and asking them, what are your numbers? Like what is realistic? And so on. And well, then there are challenges. But that’s why I say, come on, as a theoretician, you want to give experimentalists a little challenge.

The Intersection of Physics and Metaphysics

HANS BUSSTRA: Exactly. Yvette, I find it’s just, it’s beautiful to hear sort of how in this pursuit of just finding out sort of what reality is or how it behaves, I should say we are not in metaphysics yet. I want to move to metaphysics with you. This is all still about how does nature behave. And we have theories and we test them and you’re obviously at the forefront there. It’s beautiful to talk about that in further length.

But I’m just so curious what you think this is pointing to more on a metaphysical level. And of course, Roger Penrose has sort of also opened that discussion by, so as one of the first physicists again, I think after the quantum fathers, there was this period in physics where consciousness wasn’t really discussed or it could be left out of the picture. The so called sort of shut up and calculate phase.

And Roger Penrose was, I think Wheeler also played an important role. But Roger Penrose of course made sort of that with the Emperor’s New Mind idea that we said we need to see where physics and consciousness overlap. We don’t need to directly go there, but metaphysically thinking about what you’re working on. You also have a philosopher in your team. What are sort of the main philosophical discussions that sort of you have with him?

IVETTE FUENTES: Yes.

HANS BUSSTRA: That come out of this work you just described?

IVETTE FUENTES: Yes. So in my group I have several PhD students and like you said, yes, one is doing philosophy of physics. And then I have a mathematician, I have another two physicists that are more like similar to my background and then another woman who’s working on more like numerical stuff. So bridging from philosophy to the experiment because Melanie worked in an experiment before, but she then found that she likes doing simulations of the experiments.

And then I’m bridging really like these aspects. But if you come to a group meeting, we end up always talking about philosophy for hours. And I have to tell them like, okay, back to physics please.

HANS BUSSTRA: I’m sorry.

IVETTE FUENTES: Because they all love. There’s not a single student of mine that doesn’t absolutely love philosophy. And like I said, we start and then we always end up talking about philosophy.

HANS BUSSTRA: Okay, tell me about those discussions.

Philosophical Questions in Physics

IVETTE FUENTES: But I guess it comes from maybe me before coming into physics, like even as a child I was interested in philosophical questions. I was just not aware, you know, my father studied physics and then he would give me like a telescope and let’s watch and oh yeah, okay. He thought my daughter has no interest in science because I just like, yeah, I would kind of entertain that for a little bit, but not in any serious way.

But I always wanted to understand things like who am I? What am I? And things like that. But there was something that didn’t resonate very well with people around me. My mother found my questions very strange. But then I guess how that turned out as an undergraduate was working and saying, what is this time thing? I thought I understood what time is, but I actually don’t understand what it is then saying, okay, but I have an exam tomorrow, so I better just learn to work out the equation. And then I elastic these questions later.

And actually I did make a commitment with myself and I said when I grow up I’m going to try to understand what physics, what time is. And then when I was around 40 or something like that, I said like, okay, look, I’m never going to grow up, so maybe let’s start studying a little bit of time now. And I started to work with clocks. And that’s another line of research.

But already as an undergraduate, I noticed that there were some things that we used as physicists that sounded very, made sense, but that if you scratched a little bit, actually, it didn’t then. Now, bringing back closer to your question. If you can have a mass in a superposition of left and right, what’s mass? I started to notice that people just talk about it. Oh, yes. And then we have two copies of the mass. What do you mean, two copies of the mass? And then you look at the energy that, the gravitational energy and so on.

Well, even maybe the definition of mass in classical physics, if you scratch on it, if you go try to go deeper, you’re trying to see. Well, usually you end up with physics. And, well, philosophers know that, that if you start trying to go from the first principles and ask questions about what are the elements that we use, like mass, time and so on, those all become sort of fuzzy in a way when you want to describe them properly.

But let’s buy like the, you know, classical descriptions of mass or even our common sense of our experience that, okay, I hold this. It’s massive. Like, you know, you don’t need to go to university and learn equations and learn physics in order to have like an understanding of what mass is in our world. But now if you go to quantum mechanics and you tell me that the atom is everywhere, delocalized in the potential, what’s mass?

So, and I actually said that to a colleague and said, oh, that’s a stupid question or something like that, he told me. Or like, that question doesn’t make sense. And then I went back and I thought, maybe I’m not understanding something that everybody is. No, but in fact, that, well, I mean, I think you need all kinds of different personalities and physicists, some of them should not be thinking about these questions because if they did, they probably would not make progress with their experiments or with their theories.

So you need an umbrella of different types of people and minds and so on. But I kind of belong to the type that of physicists that really want to ask those questions that go a little bit sort of more to the metaphysics, maybe you would say, yeah, indeed.

HANS BUSSTRA: Because the stuff you’re saying, we have these mantras, what’s it. Space mass tells space, matter tells space time how to curve.

IVETTE FUENTES: Yes.

HANS BUSSTRA: And space time tells matter how to move. Is that it? Is that?

IVETTE FUENTES: Well, I’m not. So, so.

HANS BUSSTRA: But it’s like these mantras, but they all presuppose these concepts. And when you start sort of, but then we’re, of course, entering metaphysics. We, what is underneath is space time. Could space time be emergent from a deeper reality? And what would that deeper reality be? This is, of course, metaphysics, and physicists don’t necessarily need to go there. Right.

IVETTE FUENTES: Yeah. And then there’s actually even a place.

HANS BUSSTRA: You do need, maybe do need to address these questions. Why else would you bring in a philosopher in your team?

IVETTE FUENTES: Yes.

HANS BUSSTRA: So is it in that in your work? Metaphysics and your metaphysical assumptions do play a role, an important role that could sort of shift your.

The Role of Philosophy in Physics

IVETTE FUENTES: Oh, yeah. I mean, they play a very important role, but it’s also one of the things that I find interesting is that there’s even a little bit of a push sometimes towards physicists not to think about these things. And it could be just people wanting us to be practical and say, look, just leave that to philosophers and you do your physics and let’s make progress and let’s propose experiments, develop theories and stuff like this.

But if you really think about it, you can’t get to the stage of a meaningful experiment if you didn’t think about what is the essence of what you want to measure. That’s why my team has a philosopher, because I think that it is very important to have everything informing each step back and forth. So from the philosophy, some initial ideas, and then we try to get back to the experiment to test. But then the experiment will feed the whole line back to the philosopher. And back and forth. That would be the ideal thing that I would like to have happening at some point.

HANS BUSSTRA: What are your—I’m so curious what your discussions on metaphysics are if you have them with Roger Penrose.

Discussions with Roger Penrose on Consciousness

IVETTE FUENTES: Well, I guess Roger started first to talk to me about the collapse of the wave function. And then he started to talk about his ideas of consciousness related to that, obviously, because that’s where the starting point is. And that kind of also was a bit funny to me because when I was a student in high school, I went through a phase where I said, okay, I have to go to university. What am I going to do at university?

And I thought, well, I would really love to understand how from the interaction of atoms you get thought. Because that was the paradigm and so on. And I thought that would be very nice to understand. And I went to my uncle, who was a doctor, to my aunt’s psychologist, to my teachers. What do I have to study to understand how thought and consciousness arise from the interactions of atoms in our brains?

I couldn’t get an answer. People would say, well, medicine, no, because psychology, well, it’s more about behavior, not these questions. And then at the end of the day I was like, okay, nobody knows. Maybe I study physics because that’s interesting.

HANS BUSSTRA: And how wonderful then that you end up with the physicist who sort of addresses this head on.

IVETTE FUENTES: Yeah, and I mean, I’m embarrassed to say as well, but you can see that I don’t read much popular science because I didn’t know Lee Smolin. Of course I knew who Roger was, but I never read The Emperor’s New Mind. So I was very lucky to hear it from the emperor himself. But you know, from Roger himself how he saw consciousness. And I told that to Roger. It’s so funny that I came around this circle because I really had forgotten everything about my interest in the mind as a student. I absolutely loved it.

HANS BUSSTRA: It’s a wonderful circle. Life brings you back to that initial question.

IVETTE FUENTES: And then coming back to the spinnings of the dancings because, you know, I was telling you how I come back to things with respect to astrophysics. Now I’m testing some, doing some new things that I have to go into astrophysics and find out more about things. So I come back to these things. But this is another big example on how I came back to a starting point.

Penrose’s Argument on Consciousness and Quantum Theory

HANS BUSSTRA: And I’ll briefly sketch what Roger Penrose was dissatisfied with. At least in The Emperor’s New Mind, the argument is that there are certain problems that computationally are not solvable. And I don’t need to go through the whole argument, but it has to do with incompleteness, Gödel’s incompleteness theorem. It has to do with the halting problem and somehow the human mind that what fascinated Roger Penrose is able to solve these problems.

Therefore he thought the only behavior in nature I see that is compatible with that way of solving problems is quantum theory, where we see sort of indeterminism and is not compatible with computation as we know. So therefore I think it has something to do with quantum theory. But quantum theory is incomplete. So we need to understand physics. We need a new physics and most probably that new physics will also help us better understand quantum theory.

So that’s sort of the whole line of thinking that Roger has. I’m super curious what your, or what do you think about all of this? What’s your take on if I say Ivette, what do you think is the link between quantum mechanics and consciousness?

Two Types of Reality

IVETTE FUENTES: Okay, so I guess it brings me back to the question that we were asking somehow before about what’s mass? But I guess in a way, maybe I could phrase it different and I could say, what’s reality? What’s the fabric of reality?

Well, one of the things that I do agree with Roger is that I think there are two different types of reality. I mean, they’re obviously connected. But one, I would say it’s the quantum reality. Some colleagues see quantum mechanics as the wave function and all the mathematical formalism doesn’t really say anything about the physical world directly, but more about our stage of knowledge of the physical world, about some statistics related to it and so on. But not about physics itself.

HANS BUSSTRA: Yeah.

IVETTE FUENTES: And I don’t take that point of view. I do think that quantum mechanics speaks about physics at scales that are far from ours. And then there’s the classical world. That is the world that you and I experience described by Newton’s laws and so on. And I think that there is a transition between the quantum world and the classical world.

And obviously these worlds interact because experimentalists can go to the lab and prepare a superposition, or we can measure something and see that photons went to—the photon interfere with itself and had some quantum effects. We can see evidence of that in the laboratory. So obviously these worlds sort of interact. So trying to understand actually what the quantum world is, is also kind of going deeper into trying to understand what is the nature of reality.

HANS BUSSTRA: Yeah.

The Hard Problem of Consciousness

IVETTE FUENTES: And the elephant in the room is what about thought? So I think that—and that brings to the famous problem coined by David Chalmers, the hard problem of consciousness. The problem that I wanted to answer as a student at the university. It turns out that it’s not possible to explain how from the interaction of atoms, you get thought and consciousness from the state of physics that we have at the moment.

HANS BUSSTRA: Right.

IVETTE FUENTES: So then the question is, okay, I think this is an agreement that—well, not everybody has, but many of us have this agreement, especially people at the conference—is that with the current stage that we have of physics, and this is also what Chalmers said, we cannot explain what thought and what consciousness is.

The same thing is what Roger subscribes to that idea. And then he says where quantum mechanics goes wrong. And you know, because you have these effects of relativity, we have a new theory. And in this new theory, thought and consciousness and understanding has to play a role. It fits in there. Then it can be explained and stuff like that. I am not very sure if even under those circumstances of a new physics or—now it depends on what you call physics.

The Nature of Physics and the Observer Problem

HANS BUSSTRA: Physics is—I define it as the behavior of nature. But it can never tell us what nature truly is, which is metaphysics. But of course you can push the boundaries by knowing better how nature behaves. You can make a better bet on what nature truly is.

And I like what you said earlier in a sense that you don’t want to surrender yet to sort of that epistemic approach, the epistemic sort of quantum approach where I think QBism is one of the—on the outer edge is the position where you say we don’t know what’s out there. We only know that this theory gives us sort of predicts sort of probabilistic the behavior of nature. And that’s all the theory does.

And the superposition then is not really out there because we don’t know what’s really out there. We only know that it sort of predicts a measurement outcome. And it’s a handbook agents use that stuff like Chris Fuchs would say or Markus Müller from IQOQI in Swiss and his whole group would say what do I see next?

But where I’m curious who the I is? Who is the observer? Chris is going to give us that what the observer is. And I don’t want to put you on the spot because you’re a physicist. And physics is not about what observer who truly is. But it is the fundamental question that puzzled physicists. For instance, John Wheeler puzzled his whole life what constitutes an observer. And he had that sort of observer, subject, object divide. It’s smashed by quantum.

IVETTE FUENTES: Yes.

HANS BUSSTRA: And now we have to—but who are we in all this? I’m fascinated. I’m fired up about this question.

Quantum Mechanics as an Incomplete Theory

IVETTE FUENTES: And you know, I don’t like these divisions that sometimes they’re a bit external in the world that say you’re a physicist so you should only think about atoms. But it is key to my research to understand things in a more fundamental level then we’ve been for 100 years. We haven’t been able to understand quantum theory properly.

So I agree with Tim Maudlin, who I heard him say quantum mechanics is not a proper theory. Because a proper theory, what it does is that you have a mathematical formalism, and then you assign elements from your mathematical formalism. So a differential equation and that little constant here is the mass, and the second derivative of X with respect to T is an acceleration. So you connect to the physical world. And that gives you a theory.

But with quantum mechanics, we’re working with a theory that you have the wave function and we have no idea what the wave function is. And we all disagree and we all say different things about what the wave function is. But on the other hand, we develop lasers. We wouldn’t have lasers without quantum mechanics. And a laser is a very physical thing. You can make a hole with it on the wall.

HANS BUSSTRA: Yeah, right, I agree.

IVETTE FUENTES: So it’s very physical. So I guess because of lasers and things like that, I also have a feeling this is not just a mathematical—I mean, of course, one could invent lasers, maybe even with the point of view of QBism or something like this. I mean, it’s not excluding that you can develop technologies, but I have still a feeling that there’s something physical about it and that because it occurs at scales that are so far away from where we live, they’re difficult to understand.

HANS BUSSTRA: Yeah.

Working in Three Plus One Dimensions

IVETTE FUENTES: But still, I think we need to explain how we have this kind of physical world. And that’s another thing where I think, similar to Roger, is that, okay, maybe you can come up with a theory that has 28 dimensions. Fair enough. As long as you explain what we observe in three plus one. That’s where we live.

HANS BUSSTRA: Yeah.

IVETTE FUENTES: So then I am more of the taste of saying, why don’t we work with theories, if you can, that are in three plus one dimensions? This is something that I also have some rules with my team, with my students that I say the rule is we don’t do anything that we don’t strictly need. If we don’t need more dimensions, we don’t use them unless something really pushes us, because then we’re learning something about the world with these rules that we have.

In my team, I think we’re making a lot of progress with our new model. And it’s always somebody comes up with some idea. It’s like, do we really need it? If we don’t need it, we don’t use it. So that is kind of pushing. I think it allows you to ask the right questions, the deep questions, but still keep close to physics.

Occam’s Razor and Fundamental Assumptions

HANS BUSSTRA: Yeah. And it’s what it’s in coordinates with philosophy of science, like Occam’s razor. Be parsimonious about your assumptions. And if I’d asked you sort of on what it means to be human, on what reality fundamentally is, what is your most parsimonious sort of axiom? I mean, I could tell you mine. I’m pretty much on the sort of the first part of Descartes. I know, therefore I am sort of that consciousness is what I really know. And from there I want to be sort of careful to make my assumptions.

IVETTE FUENTES: Yes.

Questioning the Nature of Reality

HANS BUSSTRA: And then I believe that there is something real out there. I’m not saying that it’s, then, oh, that’s it. Because I really think you’re conscious too, and you’re really out there. So I’m not denying that. But I want to be careful. If this glass is really, you know, that’s sort of where I am. People who watch our channels, I’ve sort of laid out my vision in many different videos, and it’s evolving. What’s your…

IVETTE FUENTES: Okay, I’m going to go around like this where I’m going to tell you, but let me go around the branches first for a little bit. Like, let me dance before I get there. No, but we’ve been trying to unify quantum mechanics and general relativity for 100 years, and we haven’t been able to do that. And, you know, for me, it looks difficult to do these sort of things unless we take a big step somehow.

Although I do like to take little steps in my dancing, by the way. Maybe I’m doing little steps and then I wait until the grandiose moment to be a big step. But at the moment, I try to stay close to the things I know, but thinking about the circles, going back to the epicycles, on how you needed 600 circles to describe the trajectory of the planet. And then kind of the big step was it’s not a circle, it’s an ellipse.

And what that took is to get… like, it sounds like a simple thing, right? But it’s letting go of something that at the moment I can imagine was very dear to people. Circles are the perfect figure. Therefore, nature follows circles. And what that did is that it kept us in a loop, you know, thinking and keeping in a loop, thinking in the wrong way.

HANS BUSSTRA: Yeah.

IVETTE FUENTES: And, okay, then it’s painful. You have to let go of something. Right. But then you make progress. So my feeling is that these things that we’re not understanding, like for example, the incompatibilities between quantum mechanics and general relativity or the impossibility of explaining how thought emerges from the current physical theories that we have, and so on, for me, are pointing out to the fact that we’re holding on to something that is very dear to us, that if you actually challenge, many people are going to get angry at you and they’re going to tell you, don’t do that because you’re challenging the status quo. And many people don’t like that.

But I get a feeling that things themselves start taking you to a point where you have to say, look, if I want to be a serious scientist, I have to be willing to go all the way. I have to be willing to question everything. And that’s the kind of scientist I want to be. And maybe I’m wrong, you know, but I want to have that, take those risks of saying, look, I am going to maybe question things as deep as I can and then see what happens. And if we’re wrong, okay, well, we come back to where we were, right? It’s not, nothing is going to happen.

Beyond Reductionism

So, so the thing is that now I went around the branches to come to the point that you asked me, and I think that reductionism, for example, that how the current way we do physics is that we break things into little pieces, atoms and fields. And that works, right? We have lasers, thanks to reductionism, quantum computers, okay? So nobody’s going to say reductionism doesn’t work. It works amazingly good. And we’re not going to let go of reductionism ever, because it’s going to continue to give us fruits.

But maybe it’s not the right approach for everything. So maybe we need to leave the reductionism paradigm to approach certain questions. So that is one of the thoughts I have at the time. And while you were asking me what is the kind of things that you discuss with your students? And we go all the way, we question everything. And we’re saying, well, maybe the world is only made of atoms and fields, maybe, or that thought. I mean, we kind of get a feeling that thoughts are not made out of matter.

So I mean, you know, you could say, okay, yes, in your brain you have atoms, and obviously they’re doing something, and you can actually see it in the scan. But is that all that there is, or is there another thing that is also fundamental? Right? So that was what we started to discuss and learn about what were different theories. And then you get, okay, well the materialistic point of view is that everything, the fundament, what’s fundamental is atoms and fields and things like that. And then there are dual points of view that you say, okay, consciousness is also fundamental.

HANS BUSSTRA: Yeah.

IVETTE FUENTES: And then there’s some kind of interactions between them. Or you can go to the other side and say, well, only consciousness is fundamental. And then there is a… yes, there is a physical reality. I think when people say consciousness is fundamental, people get scared because they say you’re saying that physics doesn’t exist. You know, like you’re negating the physical world, which is not the case because I think we can all agree that the physical world is out here, but maybe there is a more fundamental reality from where this world that we experience sort of is underpinned by or comes from and so on.

So I think that’s the sort of things I like to question and I like to think about. And you know, I was telling you how I think the quantum reality is a physical thing and that my work is about how the classical reality emerges from the quantum. Yeah, but maybe that’s also connected to maybe some other… like maybe at a fundamental level quantum mechanics is different. And coming back to question of matter. Am I going around too much in circles?

The Physicist and the Person

HANS BUSSTRA: No, no, no, I think you are sort of… and I like that because I could, I could put… I’ve heard you in other interviews and we discussed this right before this conversation. Like we can be honest about that, sort of, about Ivette the person and Ivette the physicist and that you are personally sort of now in interviews putting on hats. Right. And I could push you on Ivette the person.

IVETTE FUENTES: Oh, I didn’t bring my physics hat.

HANS BUSSTRA: Yeah. And I don’t, I think that’s for a next conversation if we want to go more personal on your views. But I think as a physicist, what you’re doing, what I really like is that you’re in this position of dancing and not committing to a single metaphysics yet, but are willing to sort of openly look at them all. And I think that is what physics needs to do. It just has to be sort of open to all, see where sort of metaphysical assumptions bring you in studying the behavior of nature.

IVETTE FUENTES: Yes.

HANS BUSSTRA: Leading to this. And this now in my video journey so far has led me to see that Bell’s inequality tests and sort of non-locality leads many physicists to sort of doubt the metaphysical assumption of realism in a naive sense that particles are only local and influenced by local forces and are sort of much more becoming a bit more relaxed by saying, okay, an observer independent world, as physics has always sort of assumed. I mean, which… and Einstein had such hard problems of sort of coming to peace with that quantum theory might point to an observer independent reality or… sorry, that it sort of challenged that severely.

Now physicists are coming sort of like 100 years later, are now becoming at peace. And this is sort of the whole epistemic approach to quantum mechanics. But still, you have to be honest about the fact that that’s a metaphysical assumption. And then you do your physics and I hear you still dancing there. And I know as a person you are a bit more already right towards the sort perhaps consciousness first.

The Problem of Mass in Quantum Mechanics

IVETTE FUENTES: Yeah, I’m ready to turn things around, you know, because if the current way of doing things is not working, I am willing to entertain other things. But let me go back to mass again. So the current paradigm in science is materialism. So we’re saying that matter is fundamental. Okay. And, well, matter, mass. Right. And then what I’m finding in my research is that if you take that seriously, that matter is fundamental and you try to explain matter in the quantum world, mass in the quantum world, a mass being here and there at the same time, that doesn’t make sense. It hits heads when you try to do that.

So then what I did is I thought, okay, maybe there’s a different way of understanding mass in the quantum world. And that started to work. Right. And that’s kind of what we’re doing now without having to say anything about metaphysics. Right. Because I’m not doing that in my papers. I don’t go there. I don’t have to. Right. But already the question about mass in the quantum world cannot make sense in the way that we understand it in the classical world. And mass is the paradigm of materialism. Okay, you see?

HANS BUSSTRA: Yeah.

IVETTE FUENTES: That is, it’s putting things at odds with the metaphysics.

HANS BUSSTRA: We have an anomaly there that we… Yeah.

IVETTE FUENTES: That we need to do. So, yeah. So maybe considering, you know, that consciousness is fundamental, I have no idea what that would do. Like, I’ve never considered that in physics because I do physics in the standard way, although I go into these deep questions and question things as much as I want. My way of working is the normal way, you know.

HANS BUSSTRA: But it can be done. You would agree that it can be done right. If physics done from a metaphysical position that consciousness is fundamental and from there on, you just do your physics, but that’s just your core metaphysical physics. Or do you think it leads to problems?

IVETTE FUENTES: Well, I haven’t done that and I have no idea how that would look like. But if that would open up kind of possibilities, I would definitely be trying to do it and so on. So now we’re finishing. Well, I’m always saying that we’re finishing and we’re not finishing my paper. Oh yeah. My husband calls it the equation that killed Christmas, but that was a few years ago. And now it’s like the equation that killed Christmas too. And now I’m trying to finish before Christmas because three times is maybe too much.

Yeah, but, okay, but we’re hoping to publish soon and we’re going to publish the paper that’s just a physics paper and it’s going to come up with a different ontology for wave function. And it’s going to come up with things like mass in the quantum world is not making sense as it is in the classical world and how things of that sort. Right. So you can see that’s all a departure from what Roger does. But I think that’s what you want from, again, from a student. It’s like I take my own go to rebel a bit.

HANS BUSSTRA: To rebel a bit, but to do the physics. Right. Because on the physics, when it comes to the lab and doing the work there, you can shake the… that’s just doing the physics. But this is like metaphysics and it’s nice theory.

IVETTE FUENTES: No, and it’s serious. Like I do my own theory inspired on his ideas and his work and stuff like this. But I think it’s very healthy to depart. But then we want to write a paper with the student of mine who’s a philosopher to interpret, like, what is the model? Like what is this theoretical model bringing up that is new and that’s different and how can we interpret that?

And then maybe then, you know, from the conference here, I already started to get some ideas. I’m saying, oh, because I see things like you said, with my hats completely disconnected, like the stuff that I do on my day job as a physicist, working with quantum mechanics and being creative there, but always within the bounds of the theories that we are familiar with, maybe coming up with something like new, but it’s quantum and it’s gravity and all of these things. Right.

And then I always say, yes, but when I finish that and then I go back to these questions about what is the nature of reality, what am I, from a different sort of perspective. And that’s why I have my hat. And I love to go to the How the Light Gets In festival with a hat because I talk to philosophers and then I make a point of, I put my physics hat on to answer some questions. And now, okay, please take it easy on me. I’m going to take my hat off. I’m not very confident with what I want to say. I’m going to talk about my personal point of view and things like that.

And then for me, these worlds have been disconnected. And maybe after the work comes out and we see it from a philosophical point of view, then it might be that they become more connected, these two sort of ways that I have of looking at things. I mean, I would say like, I work like a physicist during the day and then in later hours, maybe I’m more of a philosopher, but I’m not because I’m not a trained philosopher. You see, I’m not a trained philosophy. I never studied philosophy. My son is studying philosophy. I’m so jealous. I’m so proud as well. I’m so, so proud of him. I’m so happy that he chose that route.

HANS BUSSTRA: Discussions with him.

IVETTE FUENTES: Yes.

HANS BUSSTRA: Yeah, you’re, yeah, it’s the two hats of physics and metaphysics. Physics and metaphysics. But in the switching of the hats, something special might happen.

IVETTE FUENTES: Right.

HANS BUSSTRA: If I’d ask you about the nature of reality with your more personal hat on, Ivette, when you come home, what would your answer then be?

The Two Hats: Materialism and Idealism

IVETTE FUENTES: Okay. So I think when I put my physics hat on, I’m a materialist, like most physicists are. And when I take my hat off, I might be more of an idealist. And the thing is, like, what will happen when I can bring these two worlds together? Which I think eventually I should be able to do that, to sort of, it’s kind of not very normal to have two different perspectives. Right. Or to have a personal perspective. But then with work, I mean, maybe it is healthy and work with one and then be able to change hats and think with the other. I don’t know.

To be honest, I sometimes get the impression that this freedom that I give myself as a person of thinking about philosophical questions and metaphysics in my own untrained way brings in creativity to my work because I don’t stick too much to, you know, oh, this brings me really nice. A way to close down with dance. You remember I told you, like, I was studying ballet.

HANS BUSSTRA: Yeah.

The Dance Metaphor: Ballet and Contemporary Physics

IVETTE FUENTES: And ballet is beautiful. I learned to love it. But ballet is very, there’s so many rules, right? You need to put your arms always like this, and there are just certain positions that are allowed. But if you want to be a real dancer, be a classical dancer, because that’s going to give you all the structure that you need and all the basics. Right. And then contemporary dance, break the rules, right? Break the rules. The arm that should be here goes there. The hips shouldn’t move, you move the hip, you start breaking things. And then you are very creative. And there’s this new dance coming up with this contemporary dance, right?

So this is the kind of physicist I want to do. Like, I can do the classical ballet. You want me to dance classical ballet? I can dance classical ballet. You know, I know how to do that. I have the training. I developed, devoted my life to do this. But I also want to be the, you know what? I forgot the name of the, I used to know this super well. Was it Graham that started contemporary dance?

HANS BUSSTRA: I’m not.

IVETTE FUENTES: And break the pattern and dance. Dance with your soul. But you say you cannot dance without the ballet training. You see what I mean? Because it’s what gives you the basics, the ability, the tools, the techniques. And that’s something I learned from my mom now, because with my mom, when I was a little girl, I said, mom, I want to dance jazz, and I want to dance these things. And she said, no, if you want to be a dancer, you learn ballet, and then you will dance whatever you want to dance, but you can’t do it the other way around.

If you learned to dance jazz right now, you won’t be able to dance flamenco. You won’t be able to dance classical dance and stuff like this. You can’t go that way around, but the other way around, you’ll see it’s true. And I had to follow the advice, and I’m very grateful for that, because she was completely right. In my older times of dancing then I was doing contemporary, flamenco, jazz, all the kinds of different dance. I now enjoy dancing more, like Latin rhythms and so on. And I can do it fairly well because of that ballet training that even at this age still holds me.

So that’s what I think I’ve done with the physics. But I don’t know, maybe I’m ready to dance a little more contemporary physics.

HANS BUSSTRA: Thank you so much, Ivette. So beautiful how you brought it all together, sort of how we started with this dancing metaphor in physics as a dance and you as a dancer now, very talented dancer, both classically, like physically dancing and within physics. That’s all beautiful.

The only sort of, I don’t know what it is, reflection on what you said on the hats would be that it might be that when you say my hat on I’m a materialist, what you’re actually saying, I’m epistemically in how we, in a scientific method, we associate that with materialism. But that’s something different than ontologically saying, I’m a materialist. And I think now there’s becoming this space in physics where you can start seeing that sort of like, that’s sort of the epistemic approach in quantum mechanics.

You just say, okay, I’m not sort of assuming that we can, that there’s an observer independent reality. I’m just taking a starting point, the observer, which is much more, I wouldn’t say it’s outright idealism, but it’s much more that ontological corner. And there’s now this space. And it seems to me that that’s where you are heading and that that’s now possible. So that physics hat where you say it’s materialist, it’s just a commitment to the scientific method. Right.

The Rigor of the Scientific Method

IVETTE FUENTES: Well, I would say, like, if we go back to the metaphor is that I would say I’m still dancing classical ballet. You know, I have a job in a company dancing classical ballet. But when I finish dancing for the company and I come home, I’m inventing this new type of dance, or I’m dancing to another rhythm because I’m not inventing this. This is a very old kind of thing that actually is kind of reviving. Right?

HANS BUSSTRA: Yeah.

IVETTE FUENTES: And I was like, okay, I’m letting myself go in a different direction. But, you know, I want to always do things with rigor and with care. Like, and that’s again, coming back to the metaphor. In ballet, you learn like, a method. And the scientific method is this rigor that you say, okay, look, you can come up with a crazy thing, okay? But there’s a mathematical rigor that you have to follow. There is a rigor in your logic that you have to follow. And then you can propose experiments to test your conclusions.

And if you do it within these bounds, that gives you the credibility, the, let’s say, the good quality of science that you want. And I always want to adhere to that. Okay, yeah. But with that safety net, let’s say because I follow this method, I want to be more free.

HANS BUSSTRA: Thank you so much.

IVETTE FUENTES: Thank you.

HANS BUSSTRA: Thank you for watching. And if you have any questions or comments, please leave them down below and we will follow up with more videos like these. And perhaps if questions come in, I’d be, I’d love to have discuss them again with you in a new setting because I really enjoyed this conversation so much. So thank you for this.

IVETTE FUENTES: Thank you so much.

HANS BUSSTRA: Yeah, it’s been about the dance of physics, but this conversation to me also has been sort of a nice dance.

IVETTE FUENTES: Yes, I love talking to you. It’s kind of, I feel very comfortable and things just flow. So it’s been a great, great pleasure talking to you and also being here at the conference.

HANS BUSSTRA: Thank you so much.

IVETTE FUENTES: Thank you.

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