Podcast: Quantum computers and labour division in ants

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Host: Benjamin Thompson

Welcome back to the Nature Podcast. This week, we’ll be finding out about another step forward in the world of quantum computing.

Host: Shamini Bundell

And learning about labour division in ant colonies. I’m Shamini Bundell.

Host: Benjamin Thompson

And I’m Benjamin Thompson.

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Host: Benjamin Thompson

First up on the show this week, reporter Adam Levy has been getting entangled in the story of a computer running a rather unusual simulation.

Interviewer: Adam Levy

Picture a computer. Now, I’m going to go out on a limb and say that you were probably thinking of your laptop, or maybe even your smartphone if you’re being smart about it. There’s a good chance you weren’t thinking of a quantum computer. These hulking, supercooled machines can take up the best part of a room but still aren’t capable of doing anything a regular computer can’t. Even so, there’s something fundamental about quantum computers that could one day give them an advantage.

Interviewee: Andrew King

A bit, which is the kind of fundamental building block of any computer program, is a binary digit which is just a 0 or a 1.

Interviewer: Adam Levy

This is computer scientist, Andrew King. But the building blocks of quantum computers aren’t bits. Instead, quantum computers use qubits. Qubits can be composed of the spin of an electron or a current in a superconducting loop. But whatever is used to make a qubit, the crucial thing is how they behave.

Interviewee: Andrew King

A qubit is a 0 or a 1, or both at the same time. The probabilities of 0 and 1 occurring, kind of interact in ways that are not possible in classical computing.

Interviewer: Adam Levy

And this otherwise impossible interaction between qubits means quantum computers can perform otherwise impossible computations. At least, that’s the theory. Here’s Davide Venturelli, also a computer scientist.

Interviewee: Davide Venturelli

Well, we cannot certainly claim, at least to my knowledge, that something that has not been done with a classical computer has been done with a quantum computer yet.

Interviewer: Adam Levy

Now, spoiler alert: we’re not bringing you news of this so-called quantum supremacy – a quantum computer performing a task no regular computer can handle. But a paper out this week does offer an important step. You see, one of the reasons that quantum computers are yet to achieve quantum supremacy and leapfrog classical computers is that they are just really hard to build. Most quantum computers only have a few handfuls of qubits - not enough to handle tasks that your laptop can’t. But one company, D-Wave, has built a machine with some 2,000 qubits.

Interviewee: Davide Venturelli

In my opinion, D-Wave really schooled the world that if you are really determined to create a quantum computer, to build a quantum computer, you can. What they did is to create a processor that exploits some effects of quantum mechanics, not all of the effects and all of the power we would want, but let’s say a minimum viable quantum computer. But then the challenge will be to be able to create algorithms and procedures and computational methods that can work with the constraints of this architecture. So, it’s a double-edged sword.

Interviewer: Adam Levy

So, these D-Wave machines may have more qubits than other quantum computers, but they’re also trickier to work with. Andrew, who we heard from earlier, works at D-Wave. He set out to simulate something that quantum computers should naturally have an advantage at.

Interviewee: Andrew King

So back in the early 80s, Richard Feynman proposed the idea of a quantum simulator where you would want to study a quantum system, and even though you know the equations that describe this system, they’re very difficult to solve. But if you can somehow program another quantum system to simulate the quantum system that you’re interested in, then you can get a big advantage over the classical simulation that you’d have to do.

Interviewer: Adam Levy

In other words, because a quantum computer is already, well, quantum, it can simulate certain quantum systems more naturally than a normal computer.

Interviewee: Andrew King

What we we’re trying to investigate with this experiment is the onset of what’s called a topological phase transition. So, it’s essentially a very exotic phase of matter in a magnetic lattice. And so, physicists have studied this system before and we wanted to see if we could make our computer instantiate this system.

Interviewer: Adam Levy

To do this, the team had to set up the computer so that it would simulate the system correctly. But they also had to find a way to read out the answer. And this isn’t a trivial task like reading something off your laptop screen. The team have to peer at what the delicate qubits are doing in the middle of the process.

Interviewee: Andrew King

It’s all really difficult because the system is extremely sensitive, and so balancing it was a big challenge. You can imagine kind of trying to present somebody a marble on a plate, and it’s really difficult to do unless you have the plate balanced very well.

Interviewer: Adam Levy

But Andrew was able to balance the plate. The D-Wave computer was able to simulate the topological phase transition in a material, getting the same results as a classical computer. Of course, the fact the team could simulate this problem using a classical computer at all indicates this is not an example of quantum supremacy. But while we might not be at a computing sea-change just yet, Andrew says the quantum computer simulation did still outperform its classical counterpart.

Interviewee: Andrew King

Yeah, the results were very good. Our results indicated that we are much, much faster, so at least thousands of times faster. The ultimate hope is that we can study materials efficiently without making them in a lab.

Interviewer: Adam Levy

With this work, a practical use for quantum computers might be that much closer. These machines which have been worked on for decades may finally be moving from theoretical playthings to actual useful research tools, simulating materials and processes that would be impossible to study on conventional hardware. For Davide, who didn’t work on this study, this is a big deal.

Interviewee: Davide Venturelli

I think the paper by Andrew King and collaborators is a very, very, very interesting development because the level of analysis is unprecedented. And I think that it will pave the way towards more experiments to be able to represent physical models, which are highly non-trivial.

Interviewer: Adam Levy

But pushing the envelope is only part of the motivation for Andrew. And he looks forward to more and more clever computations with these quantum machines.

Interviewee: Andrew King

I have to admit that half the pleasure of it is just working on a really cool problem and having things work out the way that you wantthem to. But I think that we’re kind of at a turning point with quantum computing. The competitive playing field is getting a lot more crowded and I think we’re going to show some really interesting results, and other people will show some really results, in the next few years.

Host: Benjamin Thompson

That was Andrew King who’s based at D-Wave Systems in Burnaby, Canada. You also heard from Davide Venturelli who’s at the University Space Research Association (USRA) in Washington D.C. Davide was keen to point out that USRA offer free use of their D-Wave machine through a peer-reviewed proposal.

Host: Shamini Bundell

Coming up later in the show, we’ll be hearing about a bit anthropology story – an ancient human relative that was half Neanderthal, half Denisovan. That’s coming up in the News Chat. Before then though, Anna Nagle is here with this week’s Research Highlights.

Interviewer: Anna Nagle

A group of school students in Italy have identified an unusual astronomical X-ray flare that’s left researchers stumped. The students were analysing archive data from the European Space Agency’s XMM-Newton satellite as part of a school project. They identified a short-lived burst of intense X-ray radiation coming from the galactic globular cluster NGC 6540. The flare, which lasted only 5 minutes, was both too brief and too dim to have come from any known source. Researchers who investigated the students’ finding are trying to figure out exactly where the X-ray burst originated, and think there may be similar events to be found in the satellite’s data archive. Read more from those bright sparks over Astronomy and Astrophysics.

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Interviewer: Anna Nagle

A tiny parasitic wasp may have had supersized effects by helping to stabilise global food markets. In 2008, Thailand’s production of cassava, a tuberous plant used to make starch, fell sharply after an infestation of mealybug pests damaged crops. This drop in production caused global prices of cassava starch to rise considerably. To combat the infestation, the Thai government released a wasp that selectively targets mealybugs. Researchers showed that once this pinhead-sized parasitic wasp had been introduced, cassava yields increased and global prices fell. While unable to show a direct link between the wasp and the price of cassava starch, the team say that their work sheds new light on the role that biological pest controls can play in global finance. Feast on that research over at Environmental Research Letters.

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Host: Shamini Bundell

Now, enough of all this science chat. Let’s have some small talk. Ben, what have you been up to recently?

Host: Benjamin Thompson

Oh, well, thanks for asking. I mean, I’ve still being the hot weather, you know, out in the garden and all the rest of it, just watching the bees flying around like I talked about last week.

Host: Shamini Bundell

Ah, bees. So, eusocial?

Host: Benjamin Thompson

I am indeed.

Host: Shamini Bundell

No, e-u-social.

Host: Benjamin Thompson

Yes, I am very social with people from the European Union.

Host: Shamini Bundell

The bees, Ben, I’m talking about the bees!

Host: Benjamin Thompson

Well, I’m not friends with any bees Shamini.

Host: Shamini Bundell

What I’m trying to get at is that bees are eusocial insects. They’ve evolved to live in a complex colony. In particular, a colony where tasks have been divided among specialised casts. Even their reproduction is divided up. In the case of ants, a queen does all the heavy reproductive lifting and produces sterile workers, who do things like forage and tend to larvae. All the individuals play a small but specific part in the workings of the whole colony, a bit like cells in an organism. They’re sophisticated societies, but this sophistication can’t have just started, it has to have developed, and just how that could have happened has been interesting Daniel Kronauer from the Rockerfeller University in New York. To understand how some of these traits may have come about, he’s been studying an unusual species of ant. Noah Baker gave him a call to find out more. Here’s Daniel.

Interviewee: Daniel Kronauer

So, the question is always why do you become eusocial, right? Like initially, what are the driving benefits before you have strict reproductive division of labour, right? Because of course, you don’t go from a solitary insect to something that’s highly eusocial like a honeybee. It’s a gradual process, and so there has to be certain fitness benefits for these individuals to come together in these groups. And that was kind of the big question in the current study, like, from an ecological perspective, what might the fitness benefits be that accrue to individuals that join these kinds of groups.

Interviewer: Noah Baker

In this study, you’ve worked with a particular species of ant. Tell me about these ants, because these aren’t, you know, what people might imagine of an ant colony.

Interviewee: Daniel Kronauer

Yeah, so the species that we studied, the clonal raider ant, it’s a pretty unusual species for a social insect in that the colonies don’t have queens, they only have workers but all the workers can reproduce and they do that colonially, they reproduce asexually. And so, they basically clone themselves. So, it’s quite unusual, but it’s a very nice model system to look at these kinds of questions, like for example in this study, what happens as a function of just increasing group size.

Interviewer: Noah Baker

So, you have this incredible system, this sort of colony of clones. Tell me, what is it that you did with your clones in this study?

Interviewee: Daniel Kronauer

Yeah, so we’re basically trying to monitor behavioural dynamics as we increase group size and we’re also trying to monitor the effects of fitness of increasing group size.

Interviewer: Noah Baker

And just how big are the fitness benefits that you’ve been seeing, you know, how much of a benefit does a larger group bring?

Interviewee: Daniel Kronauer

I would say very dramatic fitness benefits. So, if we look at the smallest group sizes, so these are group sizes where you actually have only one ant, these are basically not viable. In most cases, they just die. Whereas if you have the largest group sizes in our colonies, in our study the group sizes was about 16 ants, they kind of doubled the group size in every colony cycle. So basically, once a month or so you have a doubling in group size. So those are dramatic fitness differences.

Interviewer: Noah Baker

And it wasn’t just an increase in fitness that you saw either. There were behaviour changes as well - the ants started to share out the jobs, as it were.

Interviewee: Daniel Kronauer

It turns out that even if you work with extremely similar individuals - again, everyone is matched for genotype, they’re all genetically identical - the increased group size, you see very stable division of labour emerged. So, certain individuals very consistently spent more time inside the nest where they nursed the larvae and so on, and others spent much more time outside of the nest where they explored the arena and forage and so on.

Interviewer: Noah Baker

You did some modelling as well to find out exactly how this might work. What is it that you think is going on here?

Interviewee: Daniel Kronauer

Even if you have individuals that are extremely similar, you probably still have slight differences in what we think of as behaviour response thresholds. For example, imagine you share an apartment with a roommate and then there’s dirty dishes that are piling up next to the sink, and one of you has a lower response threshold to the dirty dishes. So that person will get annoyed earlier and start to do the dishes, start to clean the dishes, and so the stack of dishes gets lower and so it will never reach the response threshold of the individual, of your roommate with the higher response threshold. And so, you immediately get this division of labour just because there’s slight asymmetry in the response thresholds between the two individuals that are sharing the apartment.

Interviewer: Noah Baker

In ant terms, what are the kinds of tasks that could be analogous to washing the dishes, what are the ants’ version of that?

Interviewee: Daniel Kronauer

So, there’s a lot of different tasks in an ant colony that have to be performed but just to give you one example: the ants have to take care of the larvae inside the colony. And you could think about it this way, that the larvae need attention, they need to fed and they signal that they are hungry to the adults. And they do this probably via some sort of pheromones, some sort of chemical that the adult ants can percieve and then they respond to the larvae for example, by going out foraging. All of the ants in the colony get exposed to this larvae pheromone in the same way but then some ants have a higher threshold to respond to this pheromone, and other ants have a lower threshold, and so the ones that have a lower threshold, those are the ones that will go out and forage and try to bring back food.

Interviewer: Noah Baker

And this division of labour is what we’d call an ‘emergent’ property, so it’s not centrally controlled or planned, it’s actually just something that emerges out of a simple set of rules so things like difference of tolerance to pheromone cues, for example, in these ants. Now, that’s all very clever, but in your study, you found out that it’s not actually the key to the success of these ants and actually, that’s more linked simply just to the size of the colony.

Interviewee: Daniel Kronauer

I think one of the messages of the paper is that you actually can have very striking increases in fitness just as a matter of increasing group size even without emergent division of labour. The division of labour seems to be kind of a little bit of an add-on, so you can get very strong increases in fitness just as a function of increasing group size, even if there were no kind of behaviour specialisation between in the individuals. And if on top of that you build behaviour specialisation between individuals, you can increase fitness even more, right, it augments this increase in fitness.

Host: Shamini Bundell

That was Daniel Kronauer speaking with Noah Baker. You can read Daniel’s study over at nature.com/nature.

Interviewer: Benjamin Thompson

Well, finally this week, it’s time for the News Chat and I’m joined here in the studio by Nisha Gaind, one of the editors here at Nature. Thanks for joining us Nisha.

Interviewer: Nisha Gaind

Thanks Ben.

Interviewer: Benjamin Thompson

Okay then Nisha, for our first story today then, we’ve got something, well, that’s caused a bit of a stir.

Interviewer: Nisha Gaind

Yeah, this is a really exciting story Ben, and it’s caused a lot of chatter in our newsroom and one of our reporters has called it the human evolution find of a decade.

Interviewer: Benjamin Thompson

Well don’t keep us in suspense Nisha, what has been found?

Interviewer: Nisha Gaind

So, for the first time using genetic analysis, scientists have found a fragment of a bone that seems to belong to a person who is half Neanderthal and half Denisovan, and those are two extinct human groups.

Interviewer: Benjamin Thompson

Oh my goodness, this is the first time then that this has happened.

Interviewer: Nisha Gaind

This is the first time. It’s the first time that they have found a first-generation person of mixed ancestry, and that’s absolutely extraordinary.

Interviewer: Benjamin Thompson

Well Nisha, as I understand it, this is just another step in this story.

Interviewer: Nisha Gaind

Yeah, so this story goes back a couple of years. The work was led by researchers at the Max Planck Institute for Evolutionary Anthropology, and back in 2016 they had this bone fragment and they had already done some radiocarbon dating on it. And they found that it belonged to a hominin who lived more than 50,000 years ago. And their analysis then of the specimen’s mitochondrial DNA showed that it was mitochondrial DNA from a Neanderthal.

Interviewer: Benjamin Thompson

So, mitochondrial DNA then is inherited from your mother, so I guess this showed then that this ancient hominin’s mum was a Neanderthal. But Nisha, I guess the researchers have taken this a bit further.

Interviewer: Nisha Gaind

Exactly. So, at that time they knew only half the picture - they didn’t know the identity of the father of the person to whom this bone fragment belonged, and that’s what they’ve done now and that’s where the bombshell has dropped. So, in the later study, they have been able to sequence its whole genome and they have compared it to the DNA of three other hominins, and that is to Neanderthal, a Denisovan, and to a modern-day person from Africa.

Interviewer: Benjamin Thompson

And what have they found?

Interviewer: Nisha Gaind

So, they’ve found that around 40% of the DNA fragments from this specimen match Neanderthal DNA and another 40% match the Denisovan. And they also sequenced the sex chromosomes and they determined that the fragment came from a female and that the thickness of the bone suggested that she was about 13 years old and the researchers have now nicknamed her Denny.

Interviewer: Benjamin Thompson

Right, so equal amounts of DNA from each parent but Nisha, what are other researchers saying about this work then?

Interviewer: Nisha Gaind

Researchers are really, really excited. Kelley Harris who’s a population geneticist at the University of Washington says that these results convincingly demonstrate that the specimen is indeed a first-generation hybrid. And others agree, they say that this is a really clear-cut case and this is headed straight for the textbooks.

Interviewer: Benjamin Thompson

So, we’ve come quite a long way then, since that first paper in 2016, but it seems like there are probably still some questions that need to be answered.

Interviewer: Nisha Gaind

Absolutely. In this case, it raises questions about how Neanderthals and Denisovans interacted. For example, did they mate frequently and if they did mate frequently, why did they remain as genetically distinct populations for several hundred-thousand years?

Interviewer: Benjamin Thompson

And there are questions about geography as well, as I understand it? Denny, as we’re calling her, is thought to be about 90,000 years old now, but where she was found in this cave in Russia seems super important as well.

Interviewer: Nisha Gaind

So, there are questions about how often Neanderthals and Denisovans actually overlapped, because their encounters might have been quite rare, researchers suggest. But Neanderthals might have travelled from Western Europe where they were thought to live, to Siberia where Denisovans were thought to live, or vice versa. On the basis of the variation in this specimen’s genome, the team deduced that Denny’s Neanderthal mother was more closely related to a Neanderthal specimen that was found thousands of kilometres away in Croatia, than to another that was found less than a metre away in the same cave in Russia.

Interviewer: Benjamin Thompson

Well, let’s move on then to our second story and it couldn’t be more different to be honest with you. Last week on the show, Adam was speaking about, you know, using satellites to measure kind of differences in temperature in the oceans. And measuring these things with satellites is super important but there is maybe one hole that researchers are trying to fill. Nisha, what’s that?

Interviewer: Nisha Gaind

So that’s measurements of wind which is one of the biggest gaps in the global Earth observing system

Interviewer: Benjamin Thompson

But I know we can measure wind, you know, pretty accurately here on Earth, so why do we need this new system?

Interviewer: Nisha Gaind

Wind measurements that are made at the moment are very regional, very patchy, and they’re made my individual sources like weather balloons and aeroplane flights. Now, they’re going to use a satellite that will take a much broader view and will measure winds around the globe using a laser system from space.

Interviewer: Benjamin Thompson

Space lasers - now you are talking. But I mean Nisha, how does this new system help measure the wind?

Interviewer: Nisha Gaind

So, this new system is called Aeolus. It’s been in development at the European Space Agency for about 20 years, so meteorologists are really excited for this mission to finally be lifting off. And it's going to use an ultraviolet laser which will be shot into the Earth’s atmosphere, and the photons in this laser are going to bounce off air molecules and some of them will reflect back to the craft which from these molecules movement it will be able to discern parameters like wind speed, wind direction and wind altitude. And that’s a lot more information than researchers have ever had about wind at a global level.

Interviewer: Benjamin Thompson

So, a lot of data then Nisha, but what will this allow people to do?

Interviewer: Nisha Gaind

So, this is going to give much more detailed information on wind forecasts, especially in the tropics where many measurements aren’t taken at the moment, and by a few percent in Earth’s mid and high latitudes. Now that might not sound like a lot, but if we improve forecasts by even 2%, the value for society is many billions of dollars. Now that value comes from people being better able to forecast and better able to prepare for things like storms.

Interviewer: Benjamin Thompson

Well that sounds, you know, very positive, but what limitations might this system have?

Interviewer: Nisha Gaind

So, even though this satellite is going to hugely improve wind forecasts, there are some things that it’s not going to be able to help with, and that’s because Aeolus’ laser can’t see through thick clouds, so it won’t be able to penetrate storm systems like cyclones. But it will be able to track other phenomena such as dust blowing off the Sahara which has been an increasing problem in recent years, as well as plumes of pollutants spreading into different altitudes. And researchers are excited - they think it’s going to bring other interesting discoveries.

Interviewer: Benjamin Thompson

Right, well if they’re excited then when can they expect some results?

Interviewer: Nisha Gaind

So, we’re recording this podcast on Tuesday 21st August, and we think that it’s going to launch in the next day or two. And if all goes well, mission controllers are going to switch on that space laser by September, and that means that initial data will start coming in at the end of January next year, and that means that the information can start being inserted into national weather systems by next April.

Interviewer: Benjamin Thompson

Great, well thank you for joining us Nisha. As always, listeners, if you’d like to know more about the latest science news, don’t forget to head over to nature.com/news.

Host: Shamini Bundell

Well, that’s it for this week, but before we go I just wanted to tell you about a new film we’ve just published on a mini magnetic swarm that you can make move through a maze.

Host: Benjamin Thompson

Marvellous!

Host: Shamini Bundell

You can mosey on over to youtube.com/NatureVideoChannel for that.

Host: Benjamin Thompson

And listeners, keep an eye out for Backchat which you’ll find wherever you get your pods very soon. I’m Benjamin Thompson.

Host: Shamini Bundell

And I’m Shamini Bundell. Thanks for listening.

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