Earlier this year, NASA, in partnership with Google, acquired the world's largest quantum computer. But just what does the space agency plan to do with a device with such revolutionary potential? We talked to one of their lead researchers to find out.
Above: Artistic impression of an exoplanet. Once scaled-up sufficiently, NASA will use its quantum computers to scan the copious amounts of data acquired by Kepler and other space telescopes to identify distant planets like this one. Credit: IAU/L. Calçada
I spoke to Dr. Rupak Biswas, deputy director of the Exploration Technology Directorate at NASA's Ames Research Center in Silicon Valley. Biswas and his team are hammering away at a D-Wave quantum system that's currently crunching away at a modest 512 qubits. It may be small, but it became clear during our conversation that NASA has big plans for quantum computation — plans that will involve everything from managing huge repositories of data through to space exploration and the coordination of space-based robotic rovers.
Indeed, quantum systems have the potential — at least theoretically — to irrevocably change the way we go about computation. Unlike traditional silicon-based computers (or carbon nanotube computers for that matter), these systems tap into the eerie effects of quantum mechanics (namely superposition, entanglement, and parallelism), enabling them to mull over all possible solutions to a problem in a single instant.
According to physicist David Deutsch, a quantum system can work on a million computations at once while a standard desktop PC works on just one. Put another way, a 30-qubit system would be equal in processing power to a traditional 10 teraflop machine, which crunches trillions of operations each second.
Image: Inside the D-Wave Two quantum computer housed at the NASA Advanced Supercomputing (NAS) facility. A dilution refrigerator cools the 512-qubit Vesuvius processor to 20 millikelvin (near absolute zero) — more than 100 times colder than interstellar space. Image Credit: NASA Ames / John Hardman
These computers will help us find the most expedient solution to a complex problem. As such, they're poised to revolutionize the way we go about data analysis and optimization — including such realms as air traffic control, courier routing, protein modeling, weather prediction, database querying, and hacking tough encryption schemes.
More Than Just a Prototype
"Quantum computing has generated a lot of interest recently, particularly the ways in which the D-Wave quantum computer can be used to solve interesting problems," Biswas told io9. "We've had the machine operational since September, and we felt the time is right to give the public a little bit of background on what we've been doing."
He told me that NASA's 512 qubit machine is more than just a prototype — it's actually ready to do some work.
"It clearly demonstrates features of quantum computing, like quantum tunnelling — though it's unclear whether it demonstrates quantum entanglement," he says. "Part of the research that we're doing here at NASA Ames is to not only understand whether it has the characteristics of a quantum system, but also whether it can solve problems of interest, like hard optimization problems — problems that couldn't possibly be done on a classical machine. This is the stage we're at right now, so it's too early to know one way or another."
Biswas's team is currently looking at three very basic applications, including one that would serve as a day-planner for busy astronauts who are up in orbit.
"If you're trying to schedule or plan a whole bunch of tasks on the International Space Station, you can do certain tasks only if certain preconditions are met," he explains. "And after you perform the task you end up in another state where you may or may not be able to perform another task. So that's considered a hard optimization problem that a quantum system could potentially solve."
They're also looking to schedule jobs on supercomputers. And in fact, NASA Ames is responsible for running the agency's primary supercomputing facility. No doubt, at any instance of time they've got hundreds of individual jobs running on a supercomputer, while many others are waiting for their turn. A very difficult scenario would involve a job waiting to run — one that requires, say, 500 nodes — on a supercomputer with 1,000 nodes available.
"Which 500 of these 1,000 nodes should we pick to run the job?," he asks. "It's a very difficult scheduling problem."
The third application is the Kepler search for exoplanets. NASA astronomers use their various telescopes to look at light curves to understand whether any noticeable dimming represents a potential exoplanet as it moves across its host star. This is a massive search problem — one that D-Wave could conceivably help with.
"These are the types of applications that we're trying to run," says Biswas. "We're doing it on our D-Wave system, which is the largest in the world, but it's still not large enough to solve the really hard real world problems. But by tackling the smaller problems, we can extrapolate to how a larger problem could be solved on a larger system."
The Large Problems
So I asked Biswas to describe some of these larger problems and the kinds of jobs that NASA's upscaled quantum computer of the future could conceivably solve.
One area of consideration, says Biswas, is NASA's Earth science data. Which makes sense; they are the world's largest repository of all kinds of observational data.
"But each of these images may be at a certain wavelength, and you may not get all the information from the image," he explains. "One of the challenges there is what's called data fusion, where you try to get multiple images and somehow fuse them in some smart way so that you can garner information from a fused image that you couldn't get from a single image." (like this for example)
But just how the machine could fuse these images, and what might come out of it, is another difficult problem facing the researchers.
NASA is also heavily involved in developing the next generation of air traffic control systems. These involve not only commercial flights, but also cargo and unmanned flights. And it represents yet another hard optimization problem. Currently, much of this is done in a centralized fashion by air traffic control. But at later stages, when more distributed control is required — and highly complex variables like weather need to be taken into account — an optimization system could certainly help.
"These computers would also come in handy if we had multiple rovers on Mars or other planets," he added. "And if you wanted to manage the way all those rovers coordinate with one another, that's a good candidate for wanting to apply quantum computers.
Biswas says these systems could also help the rovers explore various kinds of rocks, or even navigate entirely new environments. Interestingly, quantum computers could also be used to develop learning algorithms — so they may play an important role in the development of artificial intelligence.
And at NASA's Ames Research Center in Silicon Valley, Biswas's team runs the supercomputers that power a significant portion of NASA's endeavors, both public and commercial.
"We see quantum computing as a natural extension of our supercomputing efforts," he told me. "In fact, our current belief is that the D-WAVE system and other quantum computers that might come out in the next few years are all going to behave as attached processors to classical silicon computers."
Which is actually quite amazing. So in the future, when a user wants to solve a large problem, they would interact with their usual computer, while certain aspects would be handed over to the quantum computer. After performing the calculation, like an optimization problem, it would send the solution back to the traditional silicon-based machine. It'll be like putting your desktop PC on steroids.
Not a Universal System
I also spoke to Biswas about the D-Wave system itself and how it works.
Image: Exterior of the D-Wave Two quantum computer installed at the NAS facility. Image Credit: NASA Ames / Nick Bonifas
"Just so we're clear, the D-Wave system is just one of many ways to leverage the effects of quantum physics," he told me. "But in order to use any quantum system, the first thing you need to have is a problem mapped in QUBO form."
A QUBO form, which stands for a Quadratic Unconstrained Binary Optimization form, is a mathematical representation of any optimization problem that needs to be solved. At this time — and as far as we know — every single quantum computer requires that the input be in QUBO form.
"And that's a serious problem," says Biswas, "because there's no known recipe to devise a problem and then map it into QUBO form. But once we get a QUBO form — which is a graph representation of the problem — we can embed this onto the architecture of the D-Wave machine."
The D-Wave processors run 512 qubits which are made up of 64 unit cells. Each unit cell is made up of 8 qubits. And each qubit is made up of a bipartite graph, so there are four quibits on the left and four on the right. Each of the four qubits are connected to the ones on the right and vice-versa. But it's not a fully connected graph.
"So what happens therefore, is after you take your problem in QUBO form and you try to embed it into the D-WAVE machine it's not a universal quantum computer. It's not like you have computer keyboard and you can just tell the machine what to do."
Essentially, the machine becomes dedicated to the task outlined by the QUBO form — a limitation that could impact scalability.
"We're also looking into the issue of perfect scaling, asking ourselves if the same concepts would apply to a larger system," he added.
Biswas told io9 that NASA is going to get a 2,048 qubit system from D-Wave in the next year or so. That will afford them the opportunity to see how scalable the system really is.