Meet the Solutionists, with Mark Scott

What if the simple act of tapping your card could put your identity at risk?

Every day, we trust encryption to protect our money, data, and digital lives. But quantum computers are advancing fast, and soon they could crack today’s security in seconds, making our current “digital locks” obsolete.

So how do we protect ourselves in a quantum world?

On this episode of The Solutionists, host Mark Scott explores the race to reinvent cybersecurity for the quantum age.

He speaks with leading mathematician Nalini Joshi, 2025 NSW Scientist of the Year, who’s bringing together some of the world’s brightest minds to develop new forms of encryption powerful enough to withstand quantum computing. She explains why maths is central to our digital future, and how mathematical thinking can unlock entirely new possibilities.

Plus, PhD researcher Prachi takes us inside a quantum control lab for a rare glimpse of a quantum computer in action.

Mark Scott  00:01

This podcast is recorded at the University of Sydney's Camperdown campus on the land of the Gadigal people of the Eora nation. They've been discovering and sharing knowledge here for 10s of 1000s of years. I pay my respects to elders past and present, and extend that respect to all Aboriginal and Torres Strait Islander people.

Prachi  00:33

Hi, I'm Prachi. I'm a PhD student here at the Quantum Control Lab, and here in this lab, we do very many things. One of the things that we do is trapped ion quantum computing, where we use trapped ions, control them with microwaves and lasers to sort of interact with them and do quantum stuff with them. I'm going to take you on a little tour of the quantum control lab. Hey, welcome! That's the sound of the sliding doors opening, which we keep them closed to maintain the pressure around the lab, because the equipment in the lab, especially the trapped ions, are very sensitive to pressure changes. So, we've got the lab split on a very special place, in the sense that it's covered by these solid cage-like system. And on the ground below, there is a big cemented block, and that's to make the mechanical movement of the floor very, very stable, so that nothing shakes on the scale of an atom or ion. This is a very, very common sound that you'll hear in quantum labs all around. The pulsing or the heartbeat sound that you're hearing is from a cryogenic pulse tube-based compressor here, which is a cooling unit on in itself. What it's doing is trying to cool something down to minus 200 degrees. Yeah, so that's very close to absolute zero, and that's something we need to maintain the accuracy of a clock-based system that we use.

Mark Scott  02:38

The digital world as we know it is at risk, a scary thought, given just how entangled it is with our physical world now. Our daily lives now rely on a network of cyber security systems, and all of these systems are under threat as we near the quantum era. In the future, quantum computers will be powerful enough to break any digital lock that exists right now. The solution: quantum proof encryption. The next problem is that this kind of encryption will require mathematics so complex that almost nobody in the world understands it right now. Now, if your head's spinning just because I said the word quantum, stick with me, because I need to introduce you to Professor Nalini Joshi, the 2025 New South Wales Scientist of the Year. Nalini is the first mathematician to win that prize, and she's the chair of applied mathematics here at the University of Sydney. And right now, she's leading a team of Australia's top maths minds in a furious effort to prepare us for our quantum future. Nalini, welcome. Paint us a picture of the future that you're worried about. What does life look like if quantum computers can break our current cybersecurity systems?

Nalini Joshi  03:59

So quantum computing comes with the promise of great achievements, and at the same time, great dangers. You've just outlined some of those dangers, but I also want to emphasise that it comes with a huge number of positive potential. The power of quantum computing will give us new materials, new medicines, new sustainable solutions. As you know, governments around the world, including ours, have been investing huge amounts into it for at least the last 10 years, and Australia in particular, is going to be spending a billion dollars building a quantum computer somewhere near Brisbane airport, I believe. But the counterpart to that story is that that same power will allow them to factor very, very large numbers, and that's where the problem lies for our current security systems. So, if you think about how we buy things online; we enter our name, our credit card details, each of those things that we enter get converted to a number. The security, the secret wall that surrounds that information, is built out of our inability to factor very large numbers on our current computers. So when the secrets have been turned into numbers, and these are very large numbers now, 4096 binary digits. That's a huge number we are trying to grapple with. First of all, transmitting those huge numbers to our banks or other people, and then for a hacker to be able to work out what that message is, they'd have to factor that very large number. And on our current computers, that will take more than our lifetimes.

Mark Scott  06:09

Right. So, I might want to crack your credit card number, but using my current computers and current processing powers, that's going to take me my lifetime. So, what does quantum computing then do to make it more viable if I wanted to be able to crack that code?

Nalini Joshi  06:28

So there is an algorithm on quantum computers. It's been known for more than 30 years now, called after the man who discovered it and invented it, Peter Shaw. His algorithm gives us a way to factor large numbers on a quantum computer in a way that we can't on a classical computer. And, when that runs on a quantum computer with sufficiently many fundamental bits, or qubits, they call it, then it will be able to factor them in a day or two, or even minutes, once they get more and more powerful.

Mark Scott  07:06

So, somebody who was trying to crack the code with the power of quantum computing could be able to do that in a very short period of time, almost an immediate period of time.

Nalini Joshi  07:19

That's right, that's right. In the time it takes you to tap your card on your eftpos machine, and it gets transmitted to the next step in the Internet era. It will be listened to, held, and cracked within a few minutes.

Mark Scott  07:37

This is disturbing stuff; our entire world is built on the security systems around non-quantum computing. As you've said, quantum computing has been coming for a while, but it's a global focus here at the University of Sydney and in the city of Sydney. We have a lot of work underway on quantum. How far in the future are we talking about? How sci-fi is this kind of breakthrough that could see this threat to our cybersecurity infrastructure?

Nalini Joshi  08:07

So, the answer depends on who you believe about the prospect of having a workable quantum computer with that many qubits. Some people say it's 5 years, some people say 10, maybe even 20. But accompanying that hardware promise is also a software development: things are getting more and more accurate in terms of what we can do with quantum computers, and that effort has made the number of estimated qubits that you need on a quantum computer smaller and smaller to be able to do this cracking. So in other words, we've got two counterparts: the hardware and the software side, and they're both going in the same direction. So I personally think it could be within 10 years time.

Mark Scott  09:01

If we think of ourselves as individual citizens and consumers, what can we realistically anticipate will change? We once used to remember passwords, now it's multi-factor authentication. What do you think the security world might look like for us in this new era that you're anticipating?

Nalini Joshi  09:23

It's hard to know, but I think it'll be like MFA, multi-factor authentication on steroids. We'll have to know a lot more about how we are pursuing, how we're using devices, how we're logging into things, whether or not the systems we're using have this extra protection or not. So right now, many companies are adopting the proposed harder algorithms to protect us from that future, but not everyone. And in particular, not every company knows what to do with this issue, even though the Australian Signals Directorate has recommended that we transition over to them by 2030.

Mark Scott  10:08

So, let's talk a little bit more about the work that you're doing to anticipate, you know, our readiness for these kinds of challenges. If the digital infrastructure that we've currently built, the security around that is going to be seriously threatened, how are we going to lock up things in the quantum world? What might quantum security look like in the future?

Nalini Joshi  10:32

So there's two parts to that story as well. So first of all, we have to protect the data that we are currently producing now, because, you know, my date of birth isn't going to change in 10 years time, my passport number may not change by then, depending on how old your passport is. So, with people already being hacked for this kind of personal data, and that information being collected, that needs to have a wall around it so that future quantum computers can't break that protocol. So that part is, I think, fairly clear, but what we're doing is creating new algorithms to make it harder and longer for numbers to be factored. But there's also the other part, the quantum computing side. You need algorithms that will work on quantum computers to protect our data when we're using quantum computers in the future. And that's a totally different beast that has several pathways in it. It's actually a fascinating direction of research, but I think again, there is a competition between the hardware and the software sides of things.

Mark Scott  11:54

I'm wondering why we haven't been talking about this more. Yilei Chen, the cryptographer, published work which I think in academic circles generated quite a lot of attention, saying that quantum computers will be able to attack certain very strong security algorithms, that there'd been a level of confidence about. A lot of reaction to that amongst researchers, but in the broader public, probably no visibility at all. But this is,we talk a lot about cyber security, why isn't this kind of far bigger threat generating more attention do you think?

Nalini Joshi  12:29

So, can I be impolite? 

Mark Scott  12:33

Go right ahead.

Nalini Joshi  12:35

So, I think probably the excitement around quantum computers has been so much around building the hardware, making the results of that somewhat reliable, making the error correction work, that we've all gone with that flow of excitement. We've all said, “oh, this is going to be like, you know, the future world. We're going to be able to go to Mars, all of that stuff.” And that excitement has been procured at the risk of attention being paid to the potential difficulties that are coming. And I think probably it's become an arena in which people want to emphasise so much of the good that they've paid less attention to the bad, but we need to do both. And I think the other side of this conversation about you know why we haven't paid attention to the bad is that it's difficult for people to understand. It requires you to know something about how quantum computers might work, about quantum mechanics, even the terminology is difficult. And it's like asking, you know, primary school students to read Charles Dickens or Henry James, and not being able to get there for a very long time.

Mark Scott  13:53

Yeah, what about our readiness to deal with this quantum world? I mean, here we are at the university, as you think through the need to have the quantum physicists who are available, those really understand the hardware and the software challenges, and to even be able to do the kind of forward thinking, even the philosophical thinking about these changes. You know, what's your read of our state of readiness?

Nalini Joshi  14:22

I think we're not ready at all, especially in Australia. And I think probably you might modify that statement elsewhere. There's a lot of exploration going on about these potential new protocols. We have suggested protocols that have been put forward as the ones that we should adopt from the National Institute of Standards and Technology in the US. People are still working on those, so we have that kind of angle to explore, but to invent new algorithms requires new mathematical ideas. It's like the factoring issue: we are converting things to numbers, we are producing large numbers, we have efficient implementations of protocols, even though these are unimaginably large numbers. But we need other ideas to create efficient protocols that will protect us even more. And not all of those angles are being explored. So even the ones that we're currently adopting, that Apple and Google and Signal have all adopted, have problems. They have gaps. We can't use them in every setting, so yes, we can use them to protect our message history, but how do we protect the tiny little parts of the internet? They're called the transport layer sockets, where you need things that are much more efficient in different ways. We don't have anything for those.

Mark Scott  16:03

Is part of the capability challenge around this, to be able to draw people from a wide array of disciplinary backgrounds and them to put their best thinking on the impact of their discipline in a quantum world? I mean, I'm interested in your pathway as a mathematician to now with a big piece of research that's coming around, the application of your mathematics given these quantum challenges.

Nalini Joshi  16:33

Yes, interdisciplinarity is essential, but I'm also struck by the fact that when you talk to somebody who works in, say, quantum information theory or people who are working in, say, search algorithms and optimization, each of them doesn't quite know where the questions are, where the dialog should be, how to benchmark each other's results. So all of that conversation has to happen with the common outlook that comes from using mathematics, common language, common ideas. And you know, I talk to people from very high-level universities, and I say to them, “why didn't you think about using this?” And they said, “oh, we didn't know that existed.” So it's very sparse. The common knowledge is very sparse between all those directions that need to talk to each other.

Mark Scott  17:42

So let's talk in practical terms about what you're doing here at the university, because you've just secured funding to tackle this cybersecurity problem with a team of top minds coming at it through a mathematical lens. So, tell us about this project that you're leading, and tell us about MathQuEST.

Nalini Joshi  18:00

So MathQuEST stands for Mathematics for Quantum Era Security and Trust, and it's a Centre of Excellence that's just been awarded by the Australian Research Council. We're bringing together mathematicians, people who work in cryptography, people who work in security of many various directions, differential privacy, optimization theory, and all of them are going to be coming together to tackle some fundamental issues for these gaps that I spoke about. We have nine universities involved, we have partner organisations, government bodies. I'm really excited about what we've been able to bring together so far, but I'm also aware of the challenges. It's going to be hard for every area to understand each other's language, so we're going to try by bringing together those common conversations, first of all, into being. But at the same time, there's this other side of making people in Australia aware, not just ordinary people, but also people in companies, people in government bodies, you know, the mums and dads who need to know about what their children might be accessing. All of these directions need to be covered. It's a daunting prospect, actually, so somehow we have to reach everyone and at the same time produce some fundamental new ideas. Of course, I come from the fundamental side of things, but I am incredibly excited by the prospect that the fundamental things I've been doing, which sound esoteric to most people, will turn out to be a lifesaver. 

Mark Scott  19:44

And can you talk a little bit about your almost academic and disciplinary pathway from mathematics, applied mathematics, but mathematics through to kind of dealing with something so specific and futuristic and challenging as this cybersecurity challenge?

Nalini Joshi  20:04

So, for most of my career, I've worked on mathematical models that help us understand how nonlinear phenomena work. So nonlinear is a term that's thrown about all over the place, but it's defined in terms of a negative so let me explain the positive side. So, if you take, say, two rulers and stack one on top of the other, then you know that the length of the combined object is the sum of the lengths of each individual ruler. That's an example of a linear system. If you have a solution of such a system, then you can add solutions and still get new solutions. So, that's very well understood. All of our applied mathematical tools, or many of them, are built on that basis that we have this structure. But almost everything we look at in the world is not linear. It's not as simple as that. If you look at how the COVID pandemic ripped through our populations, you know, the number of infected people on one day isn't the sum of the infections on the previous two days. It's the same with the weather. It's never the average, not always but you know, not the average, usually, of the previous two days. You look at waves at the beach, tsunamis are not the sums of anything else. So you need new methods, new tools, and those are the kinds of things I've been developing. Now along the way, it turns out that the models I've spent most of my career on have turned out to be incredibly impactful in areas that were unexpected. Things like estimating how boarding times on aircraft work, how bus arrival system might work. So, although they were fundamental objects, they turned out to be useful. You know, this is a way of opening up new pathways in your brain, almost. When you discover something for which you can predict ideas, behavior, it turns out to open everybody else's mind towards, “oh yeah, that's how we explain this other thing that we could never explain before.” That's the unusual way in which mathematics has become fundamental to all the sciences. It gives you a new way of thinking. Now, going from that fundamental side to the next stage of my journey, I realised that the ones that I study, the models that I study, are actually sort of evanescent versions of the constructs that underlie certain types of cybersecurity. So, in this cybersecurity setting, which is called elliptic curve cryptography, you take certain curves. These curves have lines going through them. Of course, they intersect. You have mappings that go from points to other points on the same curve. But the systems I study go from one such curve to another one. So, you're moving constantly. You're not staying on the same curve. And it turns out that gives you different phenomena that you might be able to use to create new cryptographic protocols. And that was like a light bulb moment for me, and I suddenly realized that there's this other incredible vista that we could try and explore, even with that particular type of knowledge that I came with, and that there were other such settings that one could use from mathematics. So, a fundamental idea here is the idea of non-commutativity. So, this is a fancy word for saying the order of operations matters. So you know this in real life, because when you put your shoes and socks on in the morning, you always put your socks on then your shoes. But, what happens if you did it the other way around? It's not terribly good, it's not comfortable. You put your shoes on then your socks. And that's an example of a non-commutative operation. The order matters. It turns out that in many of these contexts, the ones I spoke of going from one curve to another, or if you're thinking about other mathematical objects that we might use for cryptography, the settings give you non-commutative operations. And the weakness that I spoke of, the Shor's algorithm, assumes you have commutativity, you have things where the order of operation doesn't matter. And the exploration of this direction of whether non-commutative operations might give you more has been initiated, it's been started, but there are lots of directions that still remain unexplored, and that's what we're going to be looking at.

Mark Scott  25:06

Have you found the discovery of these applications for your initial disciplinary strength and insights exhilarating? Are you excited when you think through how this all could have a profound impact?

Nalini Joshi  25:20

Oh, absolutely. That's why I always think about mathematics as a creative art actually, because it's that suddenly seeing something, like the cubits must have seen in, you know, the art that was produced by people like Pablo Picasso and Braque and so on. The ability to see something from a different angle that one would not have done before, colours in a different way. That's just a mind-blowing experience, and that's why I do mathematics, because of that.

Mark Scott  25:53

And just finally, I know you've got a great passion for mathematics, all the way back into schools and to increase participation rates in mathematics and participation rates for for girls in particular. How do you convey that exhilaration and the practical manifestation of the power of mathematics? Do you think to young people so they can be as excited about it as you are about it?

Nalini Joshi  26:18

So I try and talk, lots and lots of talks. I go to schools. I was interviewed by Michael Kirby actually, for my old school, Fort Street. And I give talks at speech days. I try to talk individually to two children and two parents. But it's not just showing subject matter information. I think, in particular, for young people it's a question of seeing agency and discovery, a power that comes from not necessarily having to accept the templates that are constantly being thrown at you. And for girls, that template is, “no, you can't do mathematics. No, you should try and get married first. You should do things that are caring for other people first.” Those kinds of things are what I try to counter.

Mark Scott  27:20

That's Payne-Scott Professor Nalini Joshi from the University of Sydney, now also the centre director of MathQuEST and the 2025 New South Wales Scientist of the Year. You also heard from Prachi, a PhD student at the University of Sydney Nanoscience Hub. If you're inspired by the power and magic of mathematics, you'll also enjoy our episode with Eddie Wu, the high school teacher trying to bring that magic to life for his students.

Eddie Woo  27:52

Growing up, I never really fully grasped what maths was about. I've struggled with maths all my life. In fact, I kind of still do. I think that's one of the secrets to how I can teach effectively, because I still have empathy with the people I'm trying to help learn.

Mark Scott  28:09

You can listen to that episode of The Solutionists right now. If you want to hear how the best minds in the world are tackling our biggest challenges, make sure you follow the show in your favourite podcast app so you don't miss an episode. The Solutionists is a podcast from the University of Sydney produced by Deadset Studios. 

The Solutionists is a podcast from the University of Sydney, produced by Deadset Studios. Keep up to date with The Solutionists by following @sydney_uni on Facebook and Instagram, and @sydney.edu.au on Bluesky.

This episode was produced by Liam Riordan with sound design by Jeremy Wilmot. Supervising producer is Sarah Dabro. Executive editors are Kellie Riordan, Jen Peterson-Ward, and Mark Scott. Strategist is Ann Chesterman.

This podcast was recorded on the land of the Gadigal people of the Eora nation. For thousands of years, across innumerable generations, knowledge has been taught, shared and exchanged here. We pay respect to elders past and present and extend that respect to all Aboriginal and Torres Strait Islander people.