The cat that broke Einstein’s brain

So, there’s a cat in a box and it’s trapped. Most people have at least heard of the term Schrodinger’s cat. But many of us don’t actually know what it is. Science reporter Jacinta Bowler might have the answers... They spent months with their head in quantum physics land for Dead and Alive, a series of Science Friction on ABC Radio National. Today we’re unpacking what this all means, and how it could lead to a technological revolution... That could solve the world’s biggest problems: feeding more people, curing disease, optimising public transport so there are never any delays ever again... That is... If it ever gets off the ground. Follow If You're Listening on the ABC Listen app https://radio.abc.net.au/help/apps. Check out our series on YouTube: https://www.youtube.com/playlist?list=PLDTPrMoGHssAfgMMS3L5LpLNFMNp1U_Nq

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  Stop me if you've heard this one before. There's a cat in a box and it's trapped and might be alive and it might be dead. Most people have heard of the term Schrodinger's cat. I have myself used it sort of in an offhand, ah, I'm very smart way many, many times in the past. But I don't know that I quite understand the concept and what it really is and where it comes from. Science reporter Jacinta Bowler might have the answers. They spent months with their head in quantum physics land for Dead and Alive, a series of science fiction on ABC Radio National. Today, we're unpacking what all this means and how this could lead to interesting technological changes. They could solve some of the world's biggest problems.

• 1:34Speaker 03

  Feeding more people, curing disease, optimising public transport. That is, if it all ever gets off the ground. Jacinta's here. Hi Jacinta.

• 1:44Speaker 04

  Thanks for having me.

• 1:47Speaker 03

  Well, I think I understand the concept of Schrodinger's cat. At least I've seen like diagrams of a cat in a box with like poison in there or something. Can you explain to me what Schrodinger's cat is from an actual technical standpoint and what it means?

• 2:03Speaker 04

  Yeah, we'll get real nerdy real fast. I guess it's not an actual cat. I'm pretty sure the famous physicist Erwin Schrodinger wasn't a cat person. He owned a dog, apparently. It's a thought experiment that considers the idea that because of the weirdness of quantum physics, a cat could theoretically be both dead and alive at the same time. I really like what Schrodinger had to say about it himself. He said that you can imagine a cat locked up in a room of steel together with the following hellish machine, which has to be secured from direct attack by the cat.

• 2:38Speaker 04

  So, you know, you've got to make sure the cat can't get to it.

• 2:41Speaker 03

  Yeah, right. So the cat needs to be in a box with this machine that has poison in it, which may or may not kill the cat based on something that you're going to explain to me. But you, but he made it very clear that it's very important the cat cannot attack the machine.

• 2:57Speaker 04

  Yes. If the cat can get there, I mean, cats are wily buggers. I reckon they'll be able to get out of there. So basically the hellish machine has a radioactive particle inside of it and the particle may or may not decay. So in the same way that, you know, an atom can decay over time, this particular atom could decay or it might not decay. But because of the way the machine is set up, the wave function of the entire system would be expressed as the cat being a mixture of living and dead. So it's spread out in equal parts, smeared and not smeared, which is, sorry for all the, the cat lovers and the...

• 3:36Speaker 03

  No, I don't understand. It hasn't clicked for me yet. I mean, this is as far as I've got on it before, that there's a radioactive element inside a machine. There is a Geiger counter measuring the level of decay of that radioactive element. That radioactive element may or may not decay. And if it does, the Geiger counter will then smash some poison, which will then kill the cat. And from the observer's perspective, if you are outside the box and the box doesn't have any windows, you can't tell whether the cat is alive or not, because there's no way of knowing whether the radioactive element has decayed or not.

• 4:15Speaker 03

  I guess the thing is, I don't understand why we don't know if the radioactive element would decay or not. Don't we kind of know the level of decay of radioactive elements? And, and why is this a helpful thought experiment? Those are the things I don't understand at this point.

• 4:29Speaker 04

  I love it. And that's because I haven't told you probably the most important part yet. And that is superposition. So the reason why this exists at all, why this thought experiment exists, is to think about something called superposition, which is where quantum particles, specifically things like atoms and other really small particles that are affected by quantum mechanics, quantum mechanics where superposition happens and things are in multiple states at the same time. And they're in the same state at the same time until you decide that you're going to look at it. And then when you look at it, it all falls apart and it falls over. Now, this is why this thought experiment existed. However, what I really like about this thought experiment is that Schrodinger

• 5:13Speaker 04

  didn't actually believe that the cat would be the case at all. He was making fun of the idea of this superposition being something that would work in things larger than atoms. Because quantum mechanics are really weird, even at really small levels. Imagining quantum mechanics on larger objects, for example, a cat, was like absolutely silly.

• 5:35Speaker 03

  Right. So he's making kind of a joke. He's satirising the idea.

• 5:38Speaker 04

  Yes. Yeah. He's making fun of his colleagues that are like, look, bigger particles could be under superposition. But he was like, no, that doesn't make any sense. Look how silly this idea of a cat would be.

• 5:48Speaker 03

  Okay. But is that basically what we're saying here? We're saying that unless you check where something is or what it's doing, it will be in two states at once. You know, you open the box to check if the cat is alive or dead. Unless you look for it, it's in two places. When you look, it decides what place it's going to be in and it's in that place. Is that basically right?

• 6:10Speaker 04

  Okay. So let's do something a little different. Let's see if we can get this to work.

• 6:14Speaker 03

  I know you've got all sorts of other things that you want to talk about, but I'm going to, we're going to keep just circling around this until I understand.

• 6:19Speaker 04

  It's fine. Okay. So a qubit, which is the bit that is used in a quantum computer, uses this system as well. It uses superposition to be able to do the calculations that it needs to do. So you think about a computer bit, it's one and zero. Now, I want you to think about this as if it's just a switch, right? On or off, and it's electricity going down, easy, you know, no worries. Now, when you have a qubit, when it's using superposition, what happens is all of these things are carefully monitored to make sure that it all works out. It all is there perfectly. And then instead of a switch, it's a globe and the globe is being pointed at any direction.

• 6:59Speaker 04

  So it's both on, which would be the top of the switch, down, off. It'd be the bottom of the globe and then it could be anywhere in the middle of those as well. That is superposition.

• 7:12Speaker 03

  So it's like in a computer, a bit can be zero or one, but in a qubit can be zero, one, or any, you know, string of decimal points in between.

• 7:23Speaker 04

  Kind of, yeah. I use the globe analogy because I feel like it kind of changes the way you think about it. It's not like 0.777 or whatever. Like it's then becoming something entirely different from a number.

• 7:35Speaker 03

  Okay. So what you're basically saying is that quantum particles, particles that are being pushed around by quantum physics, this very upsetting dead or alive cat system that I'm pretending to understand, are helpful if we use them inside computers instead of simple one and zero bits, because they can be one, zero, or a lot of weird, strange things in between. The question I'm asking is why is it helpful to use that in a computer rather than ones and zeros, which all of us can understand?

• 8:09Speaker 04

  I am so glad you asked. Quantum computers, it doesn't really matter whether you can get Schrodinger's cat. What you need to know is that people have put in so much money and so much effort in being able to create these quantum computers, because they think that it's going to absolutely change the way that we do a lot of different systems in our lives. So that was first theorised, the idea of a quantum computer in about the 1980s by Richard Feynman. You know, he's a very famous physicist, probably one of the most apart from Einstein. And this, when it first came out, was extremely niche. Like nerds were just imagining the idea of like using a quantum computer to like think about quantum mechanics better. Like nerd on nerd, right?

• 8:51Speaker 04

  But in 1994, a guy called Peter Shaw came up with this algorithm for a quantum computer that would be able to break encryption.

• 9:03Speaker 04

  An encryption, meaning like the entirety of the way we have the internet, literally all of spy encryption, it would be a disaster for the person who didn't have the quantum computer and a huge boon for the person that did. So these companies, well, mostly governments, actually, governments, spy organisations, all of these different people went to work to try and put huge amounts of money into this industry to then be able to create this quantum computer, this weird system that no one really understands, to be able to then, well, hopefully be able to break each other's encryption and codes.

• 9:39Speaker 03

  But why would it break the codes? Why would having qubits spurting off in unpredictable and random directions be advantageous for breaking a code? Is it simply that a quantum computer that uses qubits would be so much more powerful, be able to process and store so much more data that basically it would be able to figure out the encryptions? Or is there something inherent about the way that quantum computers work that would make them particularly good at breaking the encryptions that we put on our secret information?

• 10:14Speaker 04

  It's more the first one than the second one. It's to do with something called factorisation, where you have big numbers that it's very easy to multiply two really big numbers together, really hard to pull them back apart again to work out what the two numbers were that you factorised.

• 10:28Speaker 03

  The factors?

• 10:29Speaker 04

  Factors, yeah.

• 10:30Speaker 03

  Okay, yep, yep, yep.

• 10:31Speaker 04

  Quantum computers.

• 10:32Speaker 03

  You and I can easily list the factors of 12. Don't ask me to do it, though, just, you know, I don't want to look like an idiot. Okay, so those are the things that you can multiply together in order to get 12. But it's very difficult if you've got a massive number to figure out what two numbers you multiplied together in order to get that massive number. Is that what you're saying?

• 10:49Speaker 04

  Exactly, yes. And quantum computers are very specifically good at this particular thing. So factorisation is one of the things that quantum computers can do better than a regular computer. There's a few other things as well, but it's not necessarily just the computing power, although that is a big deal. It's also the way that quantum computers work mean this is something that is possible to do as well.

• 11:11Speaker 03

  I can understand, because that is a big part of what, you know, modern cryptography is about. It's about taking all the information that you want to hide, running it through a complex mathematical equation, and then sending it somewhere. And then at the other end, they know what the mathematical equation is, so they can undo the mathematical process that you've done in order to hide the information that you're putting in there. And then at the other end, it comes back out and you can read it. A quantum computer should be able to figure out what the mathematical equation is, which would help you to read the message as it's being sent. Yeah?

• 11:48Speaker 04

  Yes. I love how deep you're into this. You're like, yes, we're going deep. I'm going to understand this at the end of this hour.

• 11:54Speaker 03

  Here at the ABC, I've heard so many discussions about quantum computers and I've heard so many reports about why quantum computers are good. There's always the cat is mentioned in some context. And I go, you keep telling me how great it is. I've been hearing how great it is for a decade, but I still don't understand why. And today, just since you're fixing that problem for me. So, okay, I'm with you so far. It's good at figuring out what maths you did to get to a result. Okay?

• 12:21Speaker 04

  Very good.

• 12:22Speaker 03

  Yeah.

• 12:22Speaker 04

  Very good at it. So this is kind of where it all started. This is where all that money came into it. There are other reasons for quantum computers too. Like you mentioned, they are more powerful simply because of the qubit situation. By being able to not just do ones and zeros, being able to do other stuff as well, you end up with a system that is more powerful than a regular computer. And so...

• 12:45Speaker 03

  And can be smaller, presumably as well.

• 12:48Speaker 04

  Yeah, so you think about how many bits are in a computer. It's lots, lots and lots and lots of bits. You can have less qubits and it's still effective in the same way. And if your factorisation gets bigger, for example, if your number gets bigger that you need to factorise, you add an extra qubit and then suddenly you can do it.

• 13:03Speaker 03

  Okay. What are they made of? Is it still just sort of electrical signals in a weird circuit board? Or is it something totally different and weird and vaguely mythological that is going on inside these computers? What are they made of?

• 13:17Speaker 04

  That is such a good question and you're the only person that's asked. So there's actually multiple different types of qubits and multiple different types of quantum computers. So we haven't even got to the point yet where we have one system, like silicon is the thing that computers go in, right? But in the really early days of computers, there was a couple of different options for what might be the computer. This is the stage we're at currently with quantum computers. There's silicon as one, there's atoms, you can also use light, I think diamonds.

• 13:50Speaker 03

  Sorry, did you say there's atoms?

• 13:52Speaker 04

  Yeah, well, yeah, so there's different, you're right. I shouldn't say that. There's, okay, so you can use different systems.

• 13:59Speaker 03

  These computers are made out of atoms.

• 14:02Speaker 04

  There are different types of atoms that you could use in there. I think one of them...

• 14:05Speaker 03

  Okay, I see.

• 14:05Speaker 04

  Yeah, so silicon's one, there's systems that use diamond, although they don't actually, the diamond is kind of where it all gets put in, light. So, yeah, there's lots of different options for building a quantum computer. And none of them have come out on top yet, which I think is really interesting because we're getting to this point where it's like, we're going to have a quantum computer, it's going to be done, except there's still multiple types of quantum computers and one hasn't come out in front. It's interesting.

• 14:31Speaker 03

  And this has been sort of bouncing around, like as you say, since like the mid 1990s. And yet, right now, we're seeing enormous spectacular amounts of investment in AI and none of it's going into quantum. All of it is going into regular old, extremely complex and microscopic semiconductors. But it's all still traditional computer systems that they are making in these data centres. They're not building quantum computers. So why is that? Why, why are we not at the point where we can use these for a practical reason?

• 15:06Speaker 04

  So we have gotten close, but we're not there yet. And I think that actually AI is a really interesting point.

• 15:13Speaker 03

  I feel like people have been saying that for a while.

• 15:15Speaker 04

  Yes, yeah.

• 15:16Speaker 03

  Saying exactly that for a really long time.

• 15:18Speaker 04

  I'm not going to be the person that tells you that the quantum computers are definitely going to be here in the next few years. I think that it is, if you talk to a scientist, we asked so many of them and all of them gave us a different number for how many years it was going to be until a quantum computer came out. We have gotten to the point, in 2019, Google and IBM had this stoush and Google did something called quantum supremacy. So that means that they did a, were able to build a quantum computer that was able to do something that a traditional supercomputer couldn't do. And that was obviously a big deal. IBM said, no, we don't think this is the case. We spoke to somebody at IBM for the story and they wouldn't speak to us for the podcast. And I think it might be because they're still mad about this almost a decade later.

• 16:03Speaker 04

  But, you know, IBM and Google are still really big players in this. But since then, the thing that they did, the quantum supremacy, the actual algorithm that they, they put out into the world, it wasn't useful. You know, it was a weird kind of system where you randomly generate numbers. That's not actually that helpful for anybody in the real world. That's not going to break any encryption. It's not going to do any of that kind of stuff.

• 16:27Speaker 03

  I also feel like we can already do that.

• 16:30Speaker 04

  Yeah.

• 16:30Speaker 03

  We can already generate random numbers. These numbers are more random, but great. How helpful.

• 16:36Speaker 04

  This is actually, it's a, it's a real nerd thing, but true randomness is very difficult. Easier for a quantum computer because it's such, it's so weird.

• 16:45Speaker 03

  Watch this, seven, 12, 728. Just keep me going. I could, I could do this.

• 16:52Speaker 04

  Perfect. Yeah, yeah, yeah. You could be the quantum computer.

• 16:55Speaker 03

  Yeah, that's it.

• 16:56Speaker 04

  So I think you make a really good point. Like, there's not that much that quantum computers can do that a regular supercomputer or AI can't do. And obviously, if you're a quantum researcher, when you speak to me, you are telling me about how good quantum computers are going to be.

• 17:15Speaker 04

  And, you know, I think in some situations, they are going to be useful. I think there are certain things that they might be useful for. I don't know how game changing it's going to be when it comes out. If the only thing that your quantum computer can do is break the encryption on the internet, that's not a good thing to invest a lot of money in.

• 17:36Speaker 03

  Yes.

• 17:37Speaker 04

  And there are other algorithms, there are things that quantum computers could do. One of the big ones that are talked about is chemistry and being able to make new molecules. That's something that other things can do as well.

• 17:47Speaker 03

  And I mean, that feels like, that feels like the sorts of things that AI is supposed to be able to do. And like, we've dumped three quarters of a trillion dollars into AI, many more than that. Uh, I think that was just the announcement in the last week or so. We're putting all of our chips on AI. So what is the, what is the, the promise that these researchers are giving you that they'll be able to provide that AI can't?

• 18:11Speaker 04

  So with quantum computers, quantum computers are able to do certain things better than anything can currently do. And some of the researchers that you speak to are like really excited about this. Like, one guy told me that he thought that this was going to be equal to the most difficult thing that humans have ever done. This is going to be equal to God, you know? Obviously, he was excited. But I do think there is going to be some things that quantum will be able to do well and potentially work with AI to be able to do that stuff. One really good example that's both good and bad, depending on how you look at it, is AlphaFold, which is a AI system that folds proteins.

• 18:51Speaker 03

  Yes, I've heard something about this. Yeah, yeah.

• 18:53Speaker 04

  Yeah, so AlphaFold looks at the protein structure and goes, I think it's folded this way. And it's an AI system. This is really difficult to do without this particular system because you have to physically look at the proteins and, and check how it's going. It takes months. AI could do it quite quickly and quite accurately. But it can't do all of it and it can't do it to the level that potentially you would like it to. Quantum, if it works, the idea is that you could use quantum alongside this to be able to, to go in deeper, to be able to do this better. I think one thing that we have to think about as a society, and AI has done this badly, you know, AI's just kind of come in and, and decided that it's everywhere. This is, AI exists now.

• 19:38Speaker 04

  I think it is a good thing to think about whether this is something that we actually want and whether quantum is something that we're willing to continue to put money in. I think it's kind of cool. I would like to see a quantum computer. I don't know whether it's going to make the huge amount of money back that's been invested into it by Google, IBM, you know, all of these big tech companies, all of these governments. Talking to the researchers, they think they're pretty close. I know they've been saying this for 30 years. But if this is something that we can do, for example, SciQuantum, it's an American company, but it's building a quantum computer in Queensland. They're putting it in Moreton Bay. And this is something that, you know, they won't talk about it. They're, they're super secretive. I got to see the, um, the chip that they use, but they wouldn't show

• 20:22Speaker 04

  me the quantum computer in action, any of that.

• 20:24Speaker 03

  Hmm. Wouldn't want you to see the thing that doesn't work yet.

• 20:28Speaker 04

  Well, but then if you talk to other scientists, if you talk to other quantum researchers, they say, no, SciQuantum, I've seen the research, SciQuantum knows what it's doing.

• 20:35Speaker 03

  Okay.

• 20:36Speaker 04

  I would love to have seen it and been able to talk to them and hope that this is something that is gonna work. They think they're gonna get to a million qubits and it's gonna be working immediately. Do I think that's gonna be the case? I'm not sure. But we are getting to the point now where, for example, other organisations are able to physically use quantum mechanics in their AI generation. And according to the people that are using it, it is useful.

• 21:10Speaker 04

  I don't know. I, I'm so wishy washy about this. I feel like I wanna be the, on the side of quantum. And talking to you, I don't, sure I am.

• 21:20Speaker 03

  Oh, look, look, I wasn't meaning to, to destroy your love of this system. I also think it's fascinating. I feel like that in the 1930s, they found some very strange thing. And we've spent nearly a hundred years being like, how can we use this for something? In the, in the same hundred years, you know, think about what we've achieved in terms of just electrifying silicon. And the story actually started with Schrödinger and Einstein going, ah, I hate that. I wish I hadn't seen that really, to be honest with you. And a hundred years later, we're kind of going, oh, well, they found it. So we should probably

• 22:02Speaker 03

  figure out what it's for and what we can do with it. But right at the start, they were like, no, no, no, thumbs down on that one. No, don't like it.

• 22:09Speaker 04

  You're so right. In Quantum's defence, obviously Einstein and Schrödinger, they're very important in quantum space and they did like other parts of quantum. But yes, no, absolutely yes. There are things that are useful, that have quantum properties or that are specifically quantum. Lasers are a really good example, MRI machines. There are lots of things in our world that use quantum properties and they wouldn't work unless they had quantum properties. The other thing that, and again,

• 22:43Speaker 03

  We like those.

• 22:44Speaker 04

  I'm, I'm telling you what the, what the researchers told me here. But when we think about the early stages of, of, of actual computers, it took them quite a while to kind of, you know, just rooting around in there to work out computers would be useful. As part of the series, I went to Cyrac, which is, you know, one of the earliest computers in Australia. It's the fifth electrical computer in the world, I believe. And this machine was so weird. It didn't use silicon. It used like vacuum tubes to be able to, to get this, you know, information from one to the other. It was huge. It was smelly. The guy who was like the weekend operator told me that it was so hot in there that sometimes you'd have to like take off your jacket. Like it was a real weird machine. But they all thought

• 23:29Speaker 04

  that this machine would be useful for like three things. They were like, okay, this is good for maths and the people that are using this will be able to use it for maths, these scientists, and that'll be all that computers are ever useful for. And the idea is that quantum computers will be similar. Once we get there, they will have more applications.

• 23:49Speaker 04

  I am a journalist and a skeptic. I don't know if that will be the case. But I probably also, if I was that guy looking at a computer and someone told me that a computer was gonna be in your pocket or in your phone or talking to you right now, there's no way I would have been like, yeah, that sounds right. I think a little bit of skepticism is good, but also maybe we need some whimsy now and then.

• 24:12Speaker 03

  I think that's true. I think the, the problem just is that, that at that time, that computer was like, well, there's either, there's this or there's, you know, just doing it with a slide rule. Whereas now it's like, well, we, there's this type of computer that we, that doesn't work. Or there's this other type of computer that has a hundred years of, eighty years of working behind it. So, you know, it's a slightly different situation. I mean, one could argue that, yeah, it's the, the, the microprocessor replaced the vacuum tube and they were sort of competitors at the time. But, you know, we're, we're not even at the stage where we know what the best type of quantum computer is. And they've been working on it for several decades. It's, it's really interesting and it's so weird.

• 24:56Speaker 03

  It's just upsettingly weird. And I'm not sure that I like it yet, but I'm getting there.

• 25:01Speaker 04

  I don't, yeah, the, the series, we, we very specifically made the series so that people can look at this and go, okay, I'm gonna make my own call on, on this. And I think that it is important to say that quantum computers have had a lot of money put into them. There's been a lot of history in this. There's been 30 years or more of this weird stuff happening and everyone going, oh, I don't really understand quantum computers. So I'm just going to like, let them do whatever they want to do. And that's fine if we're happy with that. But I also think it's important to look at this stuff and go, okay, maybe we should have a think about whether this is something that we do want to do or whether we think that AI has probably taken it over and whether we want the same thing to happen with this. We'll see what the, the scientists do. We'll see what happens in the next few years. We went to a psychic to ask them whether they thought we'd get quantum computers soon.

• 25:46Speaker 03

  Lock in a prediction.

• 25:47Speaker 04

  She didn't know. So we're gonna be on our own.

• 25:50Speaker 03

  I mean, have, have they considered asking ChatGPT or Claude how to make a quantum computer? I mean, there'd be a certain irony of that, wouldn't it?

• 25:58Speaker 04

  They're like, we refuse.

• 25:59Speaker 03

  I'd really rather not. Jacinta, what a interesting story. Thank you very much for telling us.

• 26:04Speaker 04

  Oh, thank you.

• 26:05Speaker 03

  Jacinta Bowler is ABC Science reporter and host of Dead and Alive, the latest series of science fiction for ABC Radio National. You can find all four episodes now on ABC Listen or wherever you get your podcasts.