Bits Blog: A Quantum Computing Problem Solved

University of Sydney Michael J. Biercuk, director of the Quantum Control Laboratory in the University of Sydney’s School of Physics.

Researchers at the University of Sydney and Dartmouth College said they have found a new way to design quantum memory, a key element in making quantum computing a reality. The method, they say, reduces the number of errors typically expected in quantum computing without sacrificing high-speed performance.

Quantum computing draws on certain well established, but difficult-to-control subatomic behaviors. In particular, it draws on the odd property of objects having both positive and negative charges at the same time, or for one subatomic particle affecting another without seemingly coming into physical contact with it.

Multiplied over many objects, this affords a great deal more computation than in the standard digital world of ones and zeros. Utilizing these properties could massively increase the power of certain types of computation, with implications for things like code breaking and security, materials science and facial recognition.

Compounding the difficulty of capturing and observing behavior in one of these machines, however, most quantum states exist for only the briefest fraction of a second. Keeping quantum information intact for long periods of time and keeping it relevant to the computation is one of the more daunting tasks in quantum computing. That is the problem the team says it may have solved.

The researchers used a technique called dynamical decoupling, or DD. DD has been shown to suppress errors in quantum systems by cancelling out fluctuations, something like the way one wave can smooth out a contending wave.

“The waves can overlap just the right way to build up a big amplitude or cancel out fluctuations,” Michael J. Biercuk, director of the Quantum Control Laboratory in the University of Sydney’s School of Physics, wrote in an e-mail. “In DD we need the interference to be just right such that the errors cancel.”

The team added to existing work in this field, he said, by figuring out how to break a sequence of behaviors into smaller segments that would preserve information without distorting the overall result.

“Amazingly, we were able to then show that even if we interrupted after some number of cycles, the error probability wouldn’t change much — meaning we could always ‘bound’ the error probability if we used repeated DD sequences” he said. “That is vital for a system designer who needs to know how his/her memory will perform.”

The results appear in the June 19 issue of the journal Nature Communications.

While the breakthrough is significant, Dr. Biercuk said, researchers must now show large-scale experimental demonstration of the process on a repeatable basis. The memory system must then be integrated with other error-correction algorithms to create more uniform results.

In addition to the computational uses, Dr. Biercuk said the results may be useful in the development of certain types of quantum-based communications technologies as well.

Bits: Google Buys a Quantum Computer

Kim Stallknecht for The New York Times A quantum computer developed by D-Wave Systems.

Google and a corporation associated with NASA are forming a laboratory to study artificial intelligence by means of computers that use the unusual properties of quantum physics. Their quantum computer, which performs complex calculations thousands of times faster than existing supercomputers, is expected to be in active use in the third quarter of this year.

The Quantum Artificial Intelligence Lab, as the entity is called, will focus on machine learning, which is the way computers take note of patterns of information to improve their outputs. Personalized Internet search and predictions of traffic congestion based on GPS data are examples of machine learning. The field is particularly important for things like facial or voice recognition, biological behavior, or the management of very large and complex systems.

“If we want to create effective environmental policies, we need better models of what’s happening to our climate,” Google said in a blog post announcing the partnership. “Classical computers aren’t well suited to these types of creative problems.”

Google said it had already devised machine-learning algorithms that work inside the quantum computer, which is made by D-Wave Systems of Burnaby, British Columbia. One could quickly recognize information, saving power on mobile devices, while another was successful at sorting out bad or mislabeled data. The most effective methods for using quantum computation, Google said, involved combining the advanced machines with its clouds of traditional computers.

Google bought the machine in cooperation with the Universities Space Research Association, a nonprofit research corporation that works with NASA and others to advance space science and technology. Outside researchers will be invited to the lab as well.

This year D-Wave sold its first commercial quantum computer to Lockheed Martin. Lockheed officials said the computer would be used for the test and measurement of things like jet aircraft designs, or the reliability of satellite systems.

The D-Wave computer works by framing complex problems in terms of optimal outcomes. The classic example of this type of problem is figuring out the most efficient way a traveling salesman can visit 10 customers, but real-world problems now include hundreds of such variables and contingencies. D-Wave’s machine frames the problem in terms of energy states, and uses quantum physics to rapidly determine an outcome that satisfies the variables with the least use of energy.

In tests last September, an independent researcher found that for some types of problems the quantum computer was 3,600 times faster than traditional supercomputers. According to a D-Wave official, the machine performed even better in Google’s tests, which involved 500 variables with different constraints.

“The tougher, more complex ones had better performance,” said Colin Williams, D-Wave’s director of business development. “For most problems, it was 11,000 times faster, but in the more difficult 50 percent, it was 33,000 times faster. In the top 25 percent, it was 50,000 times faster.” Google declined to comment, aside from the blog post.

The machine Google will use at NASA’s Ames Research facility, located near Google headquarters, makes use of the interactions of 512 quantum bits, or qubits, to determine optimization. They plan to upgrade the machine to 2,048 qubits when this becomes available, probably within the next year or two. That machine could be exponentially more powerful.

Google did not say how it might deploy a quantum computer into its existing global network of computer-intensive data centers, which are among the world’s largest. D-Wave, however, intends eventually for its quantum machine to hook into cloud computing systems, doing the exceptionally hard problems that can then be finished off by regular servers.

Potential applications include finance, health care, and national security, said Vern Brownell, D-Wave’s chief executive. “The long-term vision is the quantum cloud, with a few high-end systems in the back end,” he said. “You could use it to train an algorithm that goes into a phone, or do lots of simulations for a financial institution.”

Mr. Brownell, who founded a computer server company, was also the chief technical officer at Goldman Sachs. Goldman is an investor in D-Wave, with Jeff Bezos, the founder of Amazon.com. Amazon Web Services is another global cloud, which rents data storage, computing, and applications to thousands of companies.

This month D-Wave established an American company, considered necessary for certain types of sales of national security technology to the United States government.

This post has been revised to reflect the following correction:

Correction: May 17, 2013

An earlier version of this story stated that NASA was involved in the purchase of the quantum computer. While the computer will be located at NASA's facility, it was not involved in the purchase of the computer.

Bits Blog: A Quantum Computer Aces Its Test

Kim Stallknecht for The New York Times The processor of a quantum computer at D-Wave Systems’ lab in Burnaby, British Columbia.

The long-sought quantum computer, a machine potentially far ahead of today’s best supercomputers, is almost as hard to define as it is to build. For at least a few particular uses, however, the unusual computer made by D-Wave Systems now seems to be very fast indeed.

Next week a professor at Amherst College will present her findings about the performance of the D-Wave machine, which its makers say makes use of such unusual properties of quantum physics as a particle’s ability to move in one direction and its opposite at the same time.

The professor, Catherine C. McGeoch, who is the Beitzel professor in technology and society at Amherst, gave the machine a so-called optimization problem and compared the results with those generated by  popular software from I.B.M. running on a high-performance machine.

The D-Wave machine, she said, was 3,600 times as fast as the  conventional system.

“There is no sense in which this is the definitive statement about quantum computing,” Ms. McGeoch said. “I’m more interested in how well it works, not whether or not it is quantum.”

That question matters a great deal to some others in the field. While quantum properties are among the most tested and proven domains of physics, the concepts behind them — for example, suggestions that we live in one of many universes, or that objects not in direct contact can affect each other — make such properties hard to accept.

Harnessing them for the sake of computation, suggested as a possibility more than two decades ago, has proved difficult.

The optimization problem is typically something like how a traveling salesman would plan a complicated trip most effectively. Ms. McGeoch tested three problems involving optimization. In two of them, the D-Wave computer was slightly faster. In the third, it was markedly faster.

D-Wave, which was the subject of an article in The New York Times in March, has been criticized for making claims about its quantum capabilities that cannot be supported.

Over time, however, D-Wave’s performance has improved, and the skeptics have toned down their criticism. Nonetheless, D-Wave is sensitive about the issue and, even after selling a working machine to Lockheed Martin, eager to rebut the criticism.

Ms. McGeoch, who has spent more than 25 years testing computer speeds, performed the experiments while on sabbatical and was retained by D-Wave to run the tests.

D-Wave solves optimization problems by setting them in the context of energy consumption: the lowest power needed to achieve a stated outcome, which it says is quickly achieved through a quantum process, is the answer. D-Wave thinks that many problems in computing might be restated as optimization problems and that its machine could be coupled with cloud computing systems for particularly hard problems.

Ms. McGeoch said D-Wave’s chips had performed well and might have better outcomes in the future, as its machines become more powerful, and more complex optimization problems are set.

“There could be a tipping point,” she said. “If the problems get big enough, conventional systems break down. In theory, you could solve a large number of optimization problems. People don’t know how to do that conventionally without losing a lot of efficiency.”

Lockheed Martin Harnesses Quantum Technology

But a powerful new type of computer that is about to be commercially deployed by a major American military contractor is taking computing into the strange, subatomic realm of quantum mechanics. In that infinitesimal neighborhood, common sense logic no longer seems to apply. A one can be a one, or it can be a one and a zero and everything in between — all at the same time.

It sounds preposterous, particularly to those familiar with the yes/no world of conventional computing. But academic researchers and scientists at companies like Microsoft, I.B.M. and Hewlett-Packard have been working to develop quantum computers.

Now, Lockheed Martin — which bought an early version of such a computer from the Canadian company D-Wave Systems two years ago — is confident enough in the technology to upgrade it to commercial scale, becoming the first company to use quantum computing as part of its business.

Skeptics say that D-Wave has yet to prove to outside scientists that it has solved the myriad challenges involved in quantum computation.

But if it performs as Lockheed and D-Wave expect, the design could be used to supercharge even the most powerful systems, solving some science and business problems millions of times faster than can be done today.

Ray Johnson, Lockheed’s chief technical officer, said his company would use the quantum computer to create and test complex radar, space and aircraft systems. It could be possible, for example, to tell instantly how the millions of lines of software running a network of satellites would react to a solar burst or a pulse from a nuclear explosion — something that can now take weeks, if ever, to determine.

“This is a revolution not unlike the early days of computing,” he said. “It is a transformation in the way computers are thought about.” Many others could find applications for D-Wave’s computers. Cancer researchers see a potential to move rapidly through vast amounts of genetic data. The technology could also be used to determine the behavior of proteins in the human genome, a bigger and tougher problem than sequencing the genome. Researchers at Google have worked with D-Wave on using quantum computers to recognize cars and landmarks, a critical step in managing self-driving vehicles.

Quantum computing is so much faster than traditional computing because of the unusual properties of particles at the smallest level. Instead of the precision of ones and zeros that have been used to represent data since the earliest days of computers, quantum computing relies on the fact that subatomic particles inhabit a range of states. Different relationships among the particles may coexist, as well. Those probable states can be narrowed to determine an optimal outcome among a near-infinitude of possibilities, which allows certain types of problems to be solved rapidly.

D-Wave, a 12-year-old company based in Vancouver, has received investments from Jeff Bezos, the founder of Amazon.com, which operates one of the world’s largest computer systems, as well as from the investment bank Goldman Sachs and from In-Q-Tel, an investment firm with close ties to the Central Intelligence Agency and other government agencies.

“What we’re doing is a parallel development to the kind of computing we’ve had for the past 70 years,” said Vern Brownell, D-Wave’s chief executive.

Mr. Brownell, who joined D-Wave in 2009, was until 2000 the chief technical officer at Goldman Sachs. “In those days, we had 50,000 servers just doing simulations” to figure out trading strategies, he said. “I’m sure there is a lot more than that now, but we’ll be able to do that with one machine, for far less money.”

D-Wave, and the broader vision of quantum-supercharged computing, is not without its critics. Much of the criticism stems from D-Wave’s own claims in 2007, later withdrawn, that it would produce a commercial quantum computer within a year.

John Markoff contributed reporting from San Francisco.

Australians Surge in Quest to Build Quantum Computer

In an article that appeared on Thursday in the journal Nature, a team of Australian and British scientists, led from the University of New South Wales, reported that they had successfully constructed one of the basic building blocks of modern quantum computing by relying on manufacturing techniques now used by the modern semiconductor industry.

Quantum computing will potentially lead to a new generation of supercomputers that are not intended to replace today’s machines but will instead open new computing vistas, from drug and material design to code breaking, by offering speed to address a new class of problems.

“We are used to designing cars and airplanes with computers,” said Andrew Dzurak, a physicist who is director of the Australian National Fabrication Facility and lead researcher on the latest advance. “Imagine if you could start building your molecule or your material on a computer and then completely simulate its behavior.”

The basic building blocks of quantum computers are quantum bits, or “qubits.” Unlike today’s digital computers, which process information in a binary fashion based on logic states of “on” and “off,” a qubit can for brief periods represent multiple states simultaneously. Potentially, this means it is possible to tackle vast new problems by performing parallel computations using a relatively small set of qubits — perhaps as few as several hundred. The advance by Dr. Dzurak’s team involves placing a single electron — embedded in a silicon chip — in a “quantum state,” and then repeatedly measuring the state.

In February, a second group based at the University of New South Wales published an article in the journal Nature Nanotechnology reporting their advance: the construction of a single-atom transistor using a different but related design approach.

In both cases, the research teams are international. There is an increasing awareness, however, that Australian scientists have made significant advances this year toward this long-promised new type of computing.

While there is a growing consensus among scientists that working quantum computers will emerge during this decade, there is also a growing belief that they will not replace the conventional computers that are now carried in the pockets of more than half the world’s population. For one thing, most of the quantum computing approaches only worked when temperatures were cooled to near absolute zero.

Though there are only a handful of workable algorithms designed to run on quantum computers, scientists say their application may prove vastly more useful than today’s technology in simulating a wide variety of biological, chemical and physical systems. That means they could become the standard tool for a wide range of new industries, like drug and material design.

The achievements of the two teams is a payoff from an investment the Australian government began making in the 1990s.

“Both groups are highly competitive and leading in the world in what they do,” said Gerhard Klimeck, a professor of electrical and computer engineering at Purdue, who has collaborated with both groups and was a co-author of the Nature Nanotechnology paper.

Dr. Dzurak’s group’s work contrasts with a research team led by Michelle Simmons, director of the ARC Center for Quantum Computation and Communication Technology at the University of New South Wales. That group has taken an approach based on placing individual atoms using a scanning tunneling microscope, allowing great precision in building devices on an atomic scale.

The team led by Dr. Dzurak uses conventional semiconductor techniques to implant a phosphorus atom just 10 to 15 nanometers below the surface of a silicon chip. That approach has the twin advantages of using industry standards and potentially extending the individual electron’s duration in a quantum state.

The United States has federally financed, corporate and university research efforts under way to design usable quantum computers. I.B.M., for example, recently expanded its research at its Almaden laboratory in California.

Andreas Heinrich, a physicist who is a quantum researcher at I.B.M., pointed out that neither Australian group had shown the ability to interconnect multiple qubits. That capability is necessary for a quantum computer.

Dr. Dzurak said he believed that capability could be achieved as soon as a year from now.