Hey, please take a second and leave us a review on Apple Podcasts, Spotify, or wherever you listen to the podcast. Thanks a lot. Hey, welcome to Science Stuff production of iHeartRadio. I'm horhitch Ham, and today we're doing the impossible. We are going to basically teleport through walls, and we're going to do this using something called quantum tunneling, which is a phenomenon that's being used to make quantum computers a reality.
Today we're going to talk to a couple of physicists about this, including one of the people who want the Nobel Price this year for this technology. I'm going to ask him what it was like to win and what advice he has for future scientists to get ready to tunnel to the quantum world. As we answer the question what is quantum tunneling? Hey, everyone, Today we're taking another trip to the quantum world. We've talked before about what a quantum computer is and how it might basically make
passwords and things like cryptocurrency totally useless. Today we are covering how those quantum computers are being made, and most of the big ones, like the ones at Google and Amazon, use something called macroscopic quantum tunneling. So we're going to explore what that is. And the cool thing is that, thanks to a collaboration with Physics magazine, we're going to talk to one of the people who won the Nobel
Prize for it this year. But before we do that, I reached out to doctor Shohini Ghosch, a professor of physics and computer science at Wilfred Laurier University and the chief Technology officer at the Quantum Algorithms Institute in Canada. I asked her to help us explain what quantum and quantum tunneling are. Well, thank you, doctor Ghosh for talking with me.
I'm glad too, thank you for inviting me.
So maybe for those of us who are not familiar, how do you describe what quantum is?
Yeah, so, quantum mechanics is actually the theory that underpins the behavior of fundamental particles and light in the universe. So, for example, if you look at the periodic table, there's a whole bunch of elements, but all of those items are also built up of fundamental particles like electrons. And if you look at the nucleus, there are particles within
the nucleus too. Every single such microscopic particle in the universe we can actually describe using this amazing theory called quantum mechanics, and we can describe even particles of light, which we call photons. So essentially this is our description of all the matter and energy in the universe.
It's no big deal, right, That's a small theory. I guess you could say, oh, yeah, yeah.
The other important thing I'd wanted to say about quantum mechanics is that we feel like this might be something not connected to our everyday lives. But think about one of those very very important elements in that periodic table, which is silicon. Understanding silicon is essentially why we now have Silicon Valley, semiconductor industry, all of our electronics, all the devices we use every day. So it's actually part
of our lives. And we've been involved in this amazing technology revolution which started back one hundred years ago when this theory was first developed.
Amazing and phones are definitely a big part of my teenagers's lives. Maybe sometimes too.
Much, that's true, There could be too much quantum mechanics in some people's lives.
Okay, So things at the level of super small particles act very differently from what we experience in our everyday lives. They have strange properties that you might have heard of before, like the idea that you can never tell exactly where they are and where they're going. That's called the Heisenberg uncertainty principle. Or that they have a probability of being in several places at the same time. That's called superposition.
And there's something called entanglement, which is the idea that these weird quantum properties can spread out when you mix different quantum things together. Well, a result of some of these properties is something called quantum tunneling.
So quantum tunneling is a very very fundamental property that's part of this model, and what it is is it describes the behavior of these quantum particles. It's kind of like walking through walls. I don't advise anybody to try it in our real world, but yes, electrons and other quantum particles can do it, and that's quantum tunneling.
Okay, here's how doctor Goes explains what quantum tunneling is. Let's say you're standing in front of a mountain. Now you are where you are, but if you were a quantum particle, where you're going to be is kind of fuzzy. There's a probability that you're going to be one meter ahead of you, and another probability that you're going to be two meters ahead or three meters behind. That cloud
of possibilities is called a wave function. You can think of it as kind of a fog or a cloud that hovers around you that tells you where you might be next. Well, mathematically, part of that cloud could be on the other side of that mountain in front of you. Your wave function can sort of leak to the other side, and so there's a wisp of a possibility that's where
you're going to be next. So if you stand in front of that mountain long enough or enough times, you might suddenly find yourself appearing on the other side without having to climb the mountain.
If that electron doesn't have that energy, then it shouldn't be able to climb to the top of the mountain, and yet it can make it to the other side. So this very surprising way to somehow be able to not have the energy and still be able to walk through the mountain because there's no way it can climb to the top since it doesn't have the energy. That's what quantum tunneling is. It's like if we walk through the mountain.
Or it's like we created a tunnel through the mountain that's not really there. It's a quantum tunnel exactly.
There's actually no probability of being inside the mountain.
Okay, this is the strange part. It's not like you or the particle go through the mountain, because if you do, that would mean you're inside the mountain at some point. It really is like you just appear on the other side.
What's really weird about this quantum tunnel is that if you ever try to observe this particle tunneling through this mountain, you'll never find it actually ever spending any time inside the mountains. It's either on one side or the other, but it's never actually in the mountain. So that's what makes it even weirder. Okay, every time you think quantum is not weird, it gets even weirder.
Okay, you might be wondering at this point, like I was, how is this possible? How can something just be on one side of the mountain in one moment and then be on the other side of the mountain in the next moment. That seems impossible. Well, interestingly, that's something not even people who study quantum physics all their lives can't explain. Well, why do I have a probability of being on the other side of the mountain If it's impossible.
Well, I'm not saying is the next instance. It could take some time before you find the particle on the other side, but what it's doing during that time is not to dwell inside the mountain. When you say, why does it do it?
That is the.
Great mystery of quantum mechanics. Our theory tells us that this is how the description when we go and do experiments, so when we go and measure it, we can confirm whether the theory is correct or not. So in a way, the universe is showing us that this is how it works. In this universe, these kinds of robberties are possible and
we can observe it. And if all this sounds very confusing, it's okay because I think quantum scientists and physicists since the early nineteen hundreds, this is something physicists have also debated about. Is this particle actually just disappearing and appearing on two sides of a barrier? How come it doesn't spend time in the barrier. These are still things that we are grappling with.
So not even Einstein figured out what it all means.
No, I think Einstein was always deeply disturbed the implications of this serial.
He wasn't able to quantum tunnel out of No, that's good work.
Yes, he was unable to.
Okay, two recap. This is what quantum tunneling is. It's a phenomenon that you see quantum particles like electrons or protons, where if you have a particle that's up against a wall or some kind of energy barrier, that particle can sort of tunnel through that wall and appear on the other side if there is a mathematical probability that it can do that. Even though it may seem physically impossible, physicists aren't quite sure how it happens, but it does,
and it's all around us. It's what makes scanning tunneling microscopes work. And flash memory, which basically every phone and computer in the world uses. Flash memory works by pushing electrons to quantum tunnel in and out of little electronic cages that are completely insulated. When an electron is inside the cage, it's storing in of one and it stays there until you quantum tunnel it out. The device you're using right now most likely uses quantum tunneling to store
the audio file you're listening to right now. And all of this raises two questions. One, if quantum particles can tunnel through walls and barriers, could bigger objects do it too? And two, if bigger things can do this tunneling, what can you do with them? Well, as it turns out, this year's Nobel Prize for Physics was awarded to three scientists who prove that this is possible and who are
using it to make quantum computers. So when we come back, we're going to talk to one of the winners to hear how they did it, and I'm going to ask them what's it like to win a Nobel prize. Stay with us, we'll be right back.
Welcome back.
We're talking about quantum tunneling, which is something that happens in the quantum world. Small particles like electrons can sort of tunnel through walls and appear on the other side of them, almost by magic. And as I mentioned, it's what's used in scanning tunneling microscopes to take pictures of extremely small things, and it's how flash memory in your
phone and computers work now. For a long time, people thought that this strange behavior could only happen for small particles like single electrons or protons, and that once you got to bigger things, things made of millions or billions of particles, this behavior couldn't happen because of something called decoherence,
which basically means the quantum information is lost. But in nineteen eighty four, three physicists at the University of California at Berkeley showed that this assumption was wrong, and for that this year they got the Nobel Prize in Physics. To tell us what happened, here's doctor John Martinez, one of the three Pece people who won the price. Well, thank you so much, doctor Martinez for joining us. It's such a pleasure and an honor to be speaking with you.
Yeah, thank you.
Could you tell us just generally who you are and what do you do?
Well, okay, John Martinez. I've been a physicist researching quantum devices quantum computing for many decades. Right now, I was a professor at UC Santa Barbara. I've retired recently. I also worked for the Google Quantum AI team until about twenty twenty and for a couple of years. Now I've started my own company called Collab, and I'm the chief technology officer and we're just basically trying to build a useful quantum computer.
It sounds like you're very busy.
Ah, yes, I'm super busy right now after the Nobel Prize. But it's been nice, it's been wonderful. I can't complain.
What was it like to receive the announcement that you had won the prize?
Well, I wasn't expecting it at all, and this I was just so busy. I knew something was coming up, but I then thought about the date or anything. And actually my wife found out about it through email. She was up late and then she let me sleep in till five thirty in the morning, which I love my wife. She knows exactly what I need. I need my sleep. Yeah, And then she just woke me up in bed and said, hey, there's some reporters outside you want to talk to you.
And it was like, what, okay, you know, so I looked on I opened my computer and you know, lo and behold with John Clark and Michelle Deverey, and there was the announcement with me, So that was just a great honor. And it just took a kind of stunned for a few minutes and kind of got ready and I talked to some reporters. He showed up early in the morning to film me and get my immediate reaction and the like. But yeah, it's you do science because
it's great, it's interesting. There's an artistic element to it. There's a communication element, answering questions all that's really fun. But you know, getting this award is an honor, not not something one should expect. Okay, that's the best way to approach it.
Amazing live go back to you when you first did the experiment, right, and I believe at the time quantum tunneling had been proven for small particles electrons, that was well known. To take us back to before you did the experiment, somebody had proposed that it might be possible to prove quantum properties in more complicated systems, but it was a big unknown. What were you thinking at the time you and your colleagues.
First of all, I decided to join John Clark's group as a graduate student. That was in nineteen eighty because he was already doing experiments seeing quantum noise effects in electrical devices. And I thought this was really fascinating because I liked electronics. I like devices, that was my hobby
and whatever, and of course quantum mechanics fascinating. So I went to a conference down in UCLA and it was clear people were talking about it was really interesting, but people really didn't understand the experiment very well yet.
Oh what was the question?
Well, the question was could you see this macroscopic quantum tunneling effect?
Okay, here's the question, doctor Martinez, doctor John Clark, and doctor Michelle Deveray. Where tackling was could you get something bigger than an electron, maybe something millions of times bigger to quantum tunnel So instead of having one electron passing through a wall and appearing on the other side, could you get a whole bunch of them acting together to tunnel through.
And at the time, it was just murky and not very clear in the light. And I remember talking to John Clark about that and he said, yeah, well, there were some experiments that are already done, but you know, if we're going to do this, we're going to have to do something new.
How did you go about designing this experiment? He said, something new was needed.
So what the experiment is very simple. You'll have this weak link adjosin junction and you put current through it, so in some condition it looks like a superconductor. And then as you raise the current more and more, at some point it switches to the voltage state. Okay, it looks like a normal metal wire.
This is a little hard to explain, but it's basically the same picture we had before. Imagine a wire where you have electrons flowing through it, but now in the middle of the wire you put up a wall, a thin piece of something that doesn't conduct electricity. So now the electrons can flow through the wire unless the quantum tunnel through the wall. Now, as I mentioned, getting one electron to quantum tunnel through is not that hard. Happens all the time on the flash memory of your phone.
But that's only one electron at a time. To get more than one electron tunnel at the same time, you need to make the wire a super conduct.
All the electrons in a normal mettle are kind of moving around independently. But what happens is when you go into the superconducting state, they lock together and it's like they condense into what it's called a BCS state. Then it behaves like a single it's a ball if you like. So you really needed the superconducting state to see a macroscopic state.
This gets a bit technical, but if you make your wire a superconductor by making it out of a special material and making it super cold, then all the electrons and the wire start to sort of bunch together and they get linked in a quantum mechanical way so that they act like one giant electron. And that's what doctor Martinez and his colleagues were able to show. Can quantum tunnel not just one electron or a pair of electrons, but a synchronized blob of millions of electrons. Now the
secret sauce here was two things. One they added some new bells and whistles to the experiment that nobody had tried before, better filters in a microwave resonator. And two they had a lot of moxie. I love to ask you about the moment of discovery.
Well, the moment of discovery was when we did this initial experiment it didn't work, and then we discovered how to fix it, and then we got it to work, and that's when we really felt we were going to get this to work. And then it just took a lot of effort to get it to work and understand everything. It took some time to get there, but you just did experiment after experiment and it made.
Sense interesting, and so you didn't give up. Do you remember that moment where you're lifted on You're like, oh, it's working.
Yeah, I kind of remember that, the one of this initial experiment us being very pleased with that. The one moment I do remember is we were just from turning on that sample, cooled it down, I set it up, and I had an assilloscope that was tracing when it switched from the zero voltage to the vaulted state, and I could see those three peaks. Okay, up until then,
I only saw one peak. Those three peaks are just the smoking gun of quantum mechanics, to have three distinct frequencies in this system, and that's a property of quantum mechanics that tells you there's something very unusual going on with this kind of wave nature. Okay, there's something you know, really quantum going on there. But when I saw those three peaks. I knew that when I analyzed the data, this would be a totally clear explanation what was going on.
So I do remember the joy of seeing that and knowing that you know, this would be the really conclusive proof that it was the main quantum mechanics.
So that's the story of a Nobel Price winning discovery. Next, we're gonna talk about what was so significant about this discovery and how it's creating a boom in the rays to create the first really functional quantum computer. Stay with us, we'll be right back, and we're back. We're talking about
quantum tunneling. And we just heard one of the winners of this year's Nobel Prize in physics describe how he and his colleagues were able to prove that the weird properties of quantum physics don't just happen at the level of single particles like electrons or protons. If you set things up right, you can see quantum properties in bigger objects, big enough to hold in your hand. Now the question is what can you do with that. Here's Professor Shohini Coach.
So we've been talking about fundamental and small particles, but this year's Nobel Price went to a quantum tunneling of bigger things, things that are bigger than microscopic objects exactly.
So the reason that this was an important step was not because this was anything new about tunneling. This was something that was perhaps the next step in a long series of theoretical and experimental studies that were exploring quantum effects. But all of those were being done at that very
very small, individual particle level. So measuring the current generated by one electron is extremely difficult, but measuring the current generated by a million is a million times higher current, So that immediately makes the engineering piece much much easier.
Well, first of all, thank you for making things easier for engineers. I'm an engineer. We always appreciate when the physical world is easier to design for.
So I think the big advance was it led to this new possibility of creating devices and doing engineering at a larger scale, and that would lead to technologies for the future, and that's really what happened.
So the big breakthrough here is in making it easier to make quantum devices. As we said, quantum objects have some strange properties that almost seem like magic, and before this discovery, we thought the only way to make them was by handling and manipulating hiny, little fragile particles or individual atoms. But what doctor Martinez and his colleagues discovered was that you can get that same quantum magic with larger objects that are easier to work with and put together.
And one of the biggest applications so far is in making quantum computers. If you're interested in learning more about quantum computers, we did a whole episode on them earlier this year, so check that out. But the main takeaway is that quantum computers could be used for lots of interesting applications, including breaking encryption, which would make all your
passwords and all that cryptocurrency out there useless. And the idea here is that you can build quantum computers using the very same devices that the Nobel Price winning researchers made.
This became the basis for creating all kinds of devices, the most important of those being what we call these quantum computing devices that are new types of computers that use these superconducting circuits as a fundamental unit of what we call a quantum bit, which is, like, you know, we have regular bits that drive our regular computers. Quantum
bits are what are driving our quantum computers. So big companies now like IBM and Google and others are using that same idea to build out these quantum devices.
So this has led to an enormous field of people trying to build the quantum computer. Right now, there are a few thousand people who are trying to build the super conducting quantum computer.
Now here's an interesting historical fact. The idea to use this super conducting circuit doctor Martinez and his colleagues made for quantum computers may have been sparked by a chance encounter with none other than the famous physicist Richard Feynman.
So you're demonstrated your artificial atoms that can be connected by and controlled by wires.
That's Matterini, the editor of Physics magazine.
Was very clear in your mind, Oh, this is going to be a cute bit. I'm going to make quantum computers. I remember reading somewhere you were at a conference where Fineman was presenting his quantum computing ideas.
Yeah, that's right. At the end of my PhD, I came to Santa Barbara for a conference and they were talking about this physics and then Viinman gave a talk where he kind of talked about a quantum computer, and yeah, it was clear that this was really interesting and this would be something physicists would love to figure out how to do. And then it wasn't until the Factory Now algorithm by Peter Shore, which is the beginning of the nineties, that people saw that there was a way to do this,
or at least a motivation to do this. And then sometime after that there was a funding going on so that when the funding was available, we could start doing things pretty effectively.
Actually, doctor Martinez has been at the forefront of making quantum computers.
Now these systems can now form quantum bits, and we can build these systems and make a quantum computer out of it. And you know, I've been doing this for forty years now, and it took, you know, many decades. And the big culmination of all this was in twenty
nineteen when I was working for Google. We did this quantum supremacy experiment of fifty three cubits where we showed for a very mathematical problem that we could do a quantum calculation that would be very very difficult, very costly to simulate with a classical super So we show that
a quantum computer was powerful. Eventually, if we build a useful quantum computer, this is going to be used to solve real problems, and it might be part of artificial intelligence and helping with large language models kind of things. I'm thinking about how we can simulate chemistry and materials, maybe to use materials that are more ecologically mind or cheaper to mind, so that these new materials can be more common for people. That would be quite the benefit to humanity.
All Right, you magically appeared at the end of the episode. Hopefully that'd give you a good sense of what this strange quantum phenomenon is, how it impacts your everyday life, and how it might change your future. So the next time you use your phone or a computer, think about the mountain of challenges that scientists and engineers had to tunnel through to get to the other side. Thanks for joining us, See you next time you've been listening to
science stuff. Production of iHeartRadio written and produced by me or Y cham dited by Rose Seguda, executive producer Jerry Rowland, and audio engineer and mixer Kasey Pegram And you can follow me on social media to search for PhD comics and the name of your favorite platform. Be sure to subscribe to Science Stuff on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts, and please tell your friends we'll be back next Wednesday with another episode. Hey
for a post credits bonus. I thought i'd played for you two interesting moments in our conversation with doctor John Martinez. After all, it's not every day you get to interview a Nobel Prize winner. The first moment is when I asked him what it was like to make this Nobel Prize winning discovery as a graduate student and what advice he has for future young scientists. And after that, I'll play you the moment doctor Martinez said he learned something
new from me. I mean, it's definitely not every day you get to teach a Nobel Price winner anything enjoy. I'm interested in the idea that you were a graduate student when you did this work. I think that's a little rare. What was your state of mind back then as a graduate student? Were you even dreaming of a Nobel Prize or were you just interested in the problem in front of you?
No.
Bell Prize is just so unobtainable, even if you're super smart, it's not a goal anyone should have. But what a goal one should have is to do a good thesis experiment. Okay, you know I went to the conference and people were talking about it. It seemed absolutely fascinating because it was answering a very fundamental question. I don't know why lots of other people didn't jump on it, but you know, John was kind of set up to jump on it because he was looking at quantum effects and devices at
the times. And I would say also the funding at that time. He had enough general funding so that we could just do it. So it was very lucky about that.
Amazing. Well, you've been super generous with your time, John.
It's fun and I liked it very much because I think I have a better way to describe how tonly works.
Wait, what was the new way to explain it that you came up with today.
Oh, it's the fact that you just think about going through a wall, it's going to take energy to get inside that wall. You can think of as an energy argument why you bounce off.
Meaning you have to push your way through the.
You have to push your way through and there's some force and you know it's just not going to do that However, quant mechanically, you can borrow the energy to get through that for a short amount of time, and then if you go through the wall in that short amount of time, then you can pay back the energy and you're okay. So that's the way to explain it. That's great, and we should work on this in the comics.
Yeah. You know, if you send me like doodles, like napkin doodles or any kind of doodles, I can't.
Well, I'm too busy now to do that because besides doing all the nobel things, I have to go to Washington next week to meet with people and talk about quantum, and I'm trying to raise money for my company. I have like three or four jobs right now, so I can add the job of a cartoonist.