The Quantum sensing revolution

CHRIS HATZIS
Eavesdrop on Experts, a podcast about stories of inspiration and insights. Where expert types obsess, confess and profess. I’m Chris Hatzis, and in this bonus episode of EoE, our reporter Dr Andi Horvath ventures into the misunderstood world of quantum physics and, specifically, quantum sensing.

ANDI HORVATH
Here on Eavesdrop on Experts we're going to go where many fear to tread, we're going to try and understand an area of quantum physics referred to as quantum sensing. I know, it's an epic challenge but we're up for it and so are you. Quantum physics explains the behaviour of systems of stars, gases, metals, light and even inside ourselves. It's also the science behind future senses, you know, like the ones on Star Trek where they whip out a sensor and they tell you information about the life form or the alien material. The scientists we meet today are:

DAVID SIMPSON
My name's David Simpson, I'm a lecturer in physical biosciences here at the University of Melbourne, and I'm a researcher in quantum sensing in biology.

LIAM HALL
Hi, my name's Liam Hall, I'm a research fellow in quantum sensing here at the School of Physics at the University of Melbourne.

JULIA McCOEY
Hi, I'm Julia McCoey and I'm a PhD student here at the University of Melbourne and my thesis is in quantum sensing.

ANDI HORVATH
These scientists work at the level below the atom, the various subatomic particles, the particles of light that act like waves. Quantum physics is not like your normal physics that you do at school where something is there or not there. Quantum physics deals with being both there and not there at the same time.

DAVID SIMPSON
A good way to think about a quantum system is like a bubble. When the bubble exists, it's basically in a super position is what we call it. So that can be in a state of zero and one at the same time. So this bubble can exist for a certain amount of time but then that bubble is going to interact with an environment. So this could be, you could imagine it to be a flower or some sort of cactus, and depending on which environment it encounters, it's going to either pop the bubble or it can leave the bubble in that particular state. So this idea of watching how long a bubble can stay in this super position is what we're taking advantage of to measure particular environments for example.

ANDI HORVATH
These physicists are making quantum sensors to detect tiny changes in temperature or magnetic fields in say a cell or a neurone, except instead of soap bubble they use diamonds that have atomic defects in them that respond to an environment. Now we're going to talk about these later, meanwhile why is this an important field worth getting our heads around?

DAVID SIMPSON
The field's important from the point of view that we're developing new technology to put in the hands of biologists and neuroscientists and chemists to ask fundamentally new questions about how biological systems work, about how materials are made. By answering these questions we hope to be able to generate new technology, new devices that outperform current technology.

ANDI HORVATH
So even outperform MRI machines?

DAVID SIMPSON
Well that's the hope, the hope is to be able to build this instrument or this microscope that can actually pinpoint the positions of atoms in a single biomolecule for example. The group here at the University of Melbourne uses quantum sensing in materials and looking at how the nanoscale properties of materials, how magnetic are they, how can we manipulate the magnetic properties of these materials. The second research theme is to do around studying biological systems, and that's the thing that I'm focused on and that's asking the question about how we can apply these quantum sensors in interesting systems in biology.

ANDI HORVATH
Name a system, are we talking systems like disease states?

DAVID SIMPSON
One of the things that we're looking at is determining temperatures in neurons for example to ask the question about does diseases systems make neurons run hotter? We're looking at the seal mollusc to ask the question about how these amazing animals are able to synthesize the hardest biomineral. We're researching pigeons to understand how they navigate. There are a whole host of interesting questions in biology and we're just starting to scratch the surface.

ANDI HORVATH
That was David Simpson. Now meet Julia McCoy.

JULIA McCOEY
We know that birds can navigate using earth's magnetic field, but no one really knows how. There's a couple of competing theories but one of them involves there being a magnetic particle that is somewhere in the organism that's being used for the sensing. If you want to find that you're going to need the sensor to find that magnetic particle, and yeah, we're looking.

ANDI HORVATH
We're in the quantum sensing lab and you can hear the hum of the various quantum sensor microscopes. Hey, that's a picture of a mollusc, one of those funny sea creatures. Julia, why are you interested in molluscs? Because they're these funny things that stick on rocks, right?

JULIA McCOEY
They're funny things that stick on rocks, that's what they are. We're interested in them because of their teeth, so like you said they're stuck on rocks, that's because they're eating algae from the rocks and if you're going to be chewing rocks all day you're going to need to have some hard teeth. So they make their teeth from iron and they're pretty, pretty cool teeth.

DAVID SIMPSON
These teeth have been found to be the hardest biomineral that people have identified and there's real interest in understanding how these biological systems are able to engineer these sorts of materials. What we hope to be able to do is inform the chemists on how to reverse engineer this process so that we can actually make materials like this ourselves and then coat things like drill bits or armour and things like that.

ANDI HORVATH
S o this has really got some industrial application. You're looking at nature and saying hey nature does it really easily, makes these iron teeth, so where do you start?

DAVID SIMPSON
We start by looking at how these teeth actually develop. The nice thing about this chiton is that if you look at their teeth it's basically like a conveyor belt and the teeth mineralise in this ordered process. By looking at how each tooth is developing, we can get a real snapshot of how this mineralisation is taking place and what are the key components in the mineralisation. So that's the starting point.

ANDI HORVATH

In order to look at these teeth on the mollusc I believe you need a special type of microscope. Can you tell me about that?

JULIA McCOEY
Yeah, so what's really handy about these teeth and pretty cool actually, is they're magnetic. So there's magnetic properties of the different forms of iron as the teeth develop. The microscope that we're developing that uses a diamond for the quantum sensing that we do, it's able to pick out different magnetic properties so we can look at what's happening as the teeth develop and look at what's happening with the changes of the types of iron as the teeth form. So we can use that to try to figure out what's going on, how chiton are able to do the incredible things that they can do with their teeth. We have here some chiton teeth.

ANDI HORVATH
All right, gee, that's the mollusc's teeth?

JULIA McCOEY
Yeah, they're on the diamond here, we'll take it over to the microscope, just the [unclear] microscope.

ANDI HORVATH
When I got up today I never thought I'd be looking down a microscope looking at a mollusc's teeth. Oh my goodness they are, they're just like little teeth, they're sort of like vampire teeth.

DAVID SIMPSON
Shark teeth.

JULIA McCOEY
They're a little bit more like spoons, but if you cut a section through it and lay it down it looks like a shark tooth. So you've got less developed teeth at one end and the fully mature teeth at the other. So in one row of teeth you can get the whole developmental process.

ANDI HORVATH
I'm right now looking through an optical microscope, right?

DAVID SIMPSON
Yes.

ANDI HORVATH
If I wanted to detect things I can also use other types of microscope like MRIs.

DAVID SIMPSON
If you think about an MRI, an MRI is imaging magnetic fields, but it has a limited resolution so the best an MRI can do is maybe submillimetre, something on that scale. So you can't look at the magnetic properties at a cellular level, and that's the technology that we're developing. So these teeth are about 100 micron in size, so they're actually quite small, and we're imaging the magnetic properties of these teeth on a scale that's submicron.

ANDI HORVATH
Julia, what surprised you in this journey of quantum sensing?

JULIA McCOEY
Probably when I first saw the signal from a chiton tooth, yeah I was just sitting in the lab and the data was fitting and it's fitting line by line, it takes a little while and I look away for a moment and then I look back and the signal was so strong I'm sure I got up out of my chair. It was a very, very strong signal, yeah, we went from there.

ANDI HORVATH
So the quantum sensing works.

JULIA McCOEY
Yeah, it worked, definitely.

ANDI HORVATH
Okay, stop here, I need to tell you about the quantum sensor microscope. Most diamonds have defects, which is good because we can use these as quantum sensors. The defect is two carbon atoms that have been replaced by a nitrogen atom. This so-called nitrogen vacancy defect has quantum properties that you can access using laser lights and microwaves. So by shining a green laser light onto these defects they can respond to a local change in the magnetic field from, say, the magnetic tooth. The scientist just reads the amount of red light that's emitted and there's the result in beautiful never before seen high resolution. Can I see your diamonds here in the lab?

DAVID SIMPSON
Sure, so we have many and in different forms. The ones that Julia's been working with are what we call single crystal diamond, so these are like diamonds you would have in your ring for example. These are sheets basically of diamond, the size comes in about four by four millimetres and they're about 100 micron thick, which is about the size of a human hair. What's even less impressive from a science perspective is what's called nanodiamond.

ANDI HORVATH
Show me, show me.

DAVID SIMPSON
Nanodiamond is what we would typically put into living cells. So the nanodiamond powder just looks like talcum powder.

ANDI HORVATH
It's grey powder.

DAVID SIMPSON
So it's imagine diamond crushed up into incredibly small pieces.

ANDI HORVATH
It's so ugly, it's so unimpressive.

DAVID SIMPSON
But the beautiful aspect of these nanodiamonds is the fact that they can host these single quantum systems.

ANDI HORVATH
Okay, so this is your quantum sensor. This is kind of like, you know in Star Trek when they get out their little equipment and they start scanning things, they're probably using quantum sensors, right?

DAVID SIMPSON
Exactly, I'm pretty sure it's made of diamond.

ANDI HORVATH
Now give us the layout, the specs. You shined a laser onto a diamond with a defect, is that right?

DAVID SIMPSON
Yes, exactly.

ANDI HORVATH
Just pretend I'm your student, talk me through it, what am I going to do?

DAVID SIMPSON
So we have these atomic defects, these nitrogen vacancy centres. These are located near the very surface of the diamond. We come in with a green laser and we excite these defects. So basically the green laser interacts with these sensors and these sensors glow red, so they generate this red fluorescence. It's this red fluorescence or red light that we measure and that helps us determine changes in magnetic field and helps us be able to image magnetic field.

ANDI HORVATH
What has surprised you in your adventures in the quantum sensing world?

DAVID SIMPSON
One of the things that really surprised me I remember was back in 2010, this really changed the trajectory of the research that we do. We were sitting in the lab, it was midnight I remember and we were looking at the first nanodiamond experiments that we were performing in a living cell. So we had a set of [HeLa] cells and we had nanodiamonds that were injected into these HeLa cells, and we were measuring the quantum properties from these nanodiamonds. This was something I never thought we'd actually be able to do. We measured the quantum properties over this 12 hour period from midnight until the morning and that really then changed the game for us and showed that you can actually use these quantum systems in biology and they can provide really useful information. So that was something that really surprised me.

ANDI HORVATH
Next up is Liam Hall, a postdoc in the same lab and work unit.

LIAM HALL
I was kind of prepared for seeing that behaviour in real life. I knew about what this sort of quantum behaviour was that was expected and everything like that, I think what's probably surprised me the most is how, I don't want to say quickly but how ready these sort of systems are that we're always just a mathematical playground and everything like that. How ready they are now to start to be translated towards real technology. I suppose we talked about a few projects now that we hope are leading towards whether it be medical diagnostics or ways of doing interdisciplinary research to help chemistry departments and biology departments, neuroscience and so on. It's sort of gone from this oh this is a really cool system to look at and to back up what's in the textbook, to something that we can actually use that's useful.

ANDI HORVATH
What misconceptions do people have about your area, Liam?

LIAM HALL
Well I guess you get brought up through your education to think that biology and physics and chemistry are these distinct disciplines, and we're seeing with the amount of overlap and interaction that we get with groups in those areas, particularly the bio space but we have a lot to do with chemists as well, that the really good questions in these disciplines can't be answered on their own. There's a lot to be gained by having different disciplines help each other. Interdisciplinarity is a bit of a buzzword at the moment but there's certainly a lot of truth to why it works and how we can help assist with those areas.

ANDI HORVATH
Julia, you're a great example of interdisciplinary research. You started off in biology but you've ended up a physicist.

JULIA McCOEY
Yeah, a bit of both, everything Liam said there it's true, you can't have one without the other. It's actually the reason I went to do the physics was because if I really want to understand what's going on in biology I've got to understand physics.

LIAM HALL
When I came to Melbourne that was to create this single photo source, so I was working with a team of people to do that and we successfully commercialised that product. Since then that's when I met Lloyd, so Lloyd Hollenberg is our group leader and he is the deputy director of the Centre for Quantum Computing. The other unique thing about Lloyd is that he straddles the world of quantum computing and quantum sensing, so he's developed a lot of ground-breaking new research in both of these fields and he's a real pioneer in quantum physics. We had this journey of looking at more the fundamental properties of this quantum system and what we can actually do with it and then we started interacting with people from biology and neuroscience and it's just taken on a life of its own.

ANDI HORVATH
Okay quantum sensing team, what do you want us to think about next time we see a diamond?

DAVID SIMPSON
Whenever I see a diamond I don't think about it as a hard rare stone free of defects, which is what most people are trying to identify when they go buying these things. I think the beauty of diamond is really in these atomic defects, so next time you look at your ring you can think about the fact that there are millions of single quantum systems in that diamond that we can use as a resource for new technology and new devices.

ANDI HORVATH
There you have it, you survived an adventure in quantum physics called quantum sensing. I'm going back to the lab to talk to the other PhD students just for fun. Wow, which quantum sensor microscope do you like to use?

STUDENT
I like to use the Argus .

ANDI HORVATH
Why is it called the Argus?.

STUDENT
Because it sees everything.

CHRIS HATZIS
Thanks to Dr David Simpson, lecturer in physical biosciences, Dr Liam Hall, research fellow in quantum sensing, and Julia McCoey, PhD student, all at the School of Physics, University of Melbourne. And thanks to our reporter Dr Andi Horvath.

Eavesdrop on Experts - stories of inspiration and insights - was made possible by the University of Melbourne. This bonus episode was recorded on March 27, 2018. You’ll find a full transcript on the Pursuit website. Audio engineering by Arch Cuthbertson, co-production by Dr Andi Horvath and Silvi Vann-Wall. Eavesdrop on Experts is licensed under Creative Commons, Copyright 2018, The University of Melbourne. If you enjoyed this podcast, drop us a review on iTunes, and check out the rest of the episodes in our archive. I’m Chris Hatzis, producer and editor. Join us again next time for another Eavesdrop on Experts.