Microsoft has yet to even build a qubit. But in the kind of paradox that can be expected in the realm of quantum physics, it may also be closer than anyone else to making quantum computers practical. The company is developing a new kind of qubit, known as a topological qubit, based largely on that 2012 discovery in the Netherlands. There’s good reason to believe this design will be immune from the flakiness plaguing existing qubits. It will be better suited to mass production, too. “What we’re doing is analogous to setting out to make the first transistor,” says Peter Lee, Microsoft’s head of research. His company is also working on how the circuits of a computer made with topological qubits might be designed and controlled. And Microsoft researchers working on algorithms for quantum computers have shown that a machine made up of only hundreds of qubits could run chemistry simulations beyond the capacity of any existing supercomputer.
The optimization and simulation problems that DWave solves are the most important and economically valuable problems. DWave seems to be providing actual commercial scale solutions. Google is a customer and Google is trying to leverage the Dwave work with a system that could leverage error correction. Dwave is doubling qubits every year and will have a commercial version with 1152 qubits in early 2015. If DWave is scaling the performance then competitors will face a substantial challenge to catchup
Michael Freedman, the instigator and technical mastermind of Microsoft’s project, admits to feeling inferior. “When you start thinking about quantum computing, you realize that you yourself are some kind of clunky chemical analog computer,” he says. Freedman, who is 63, is director of Station Q, the Microsoft research group that leads the effort to create a topological qubit, working from a dozen or so offices on the campus of the University of California, Santa Barbara. Fit and tanned, he has dust on his shoes from walking down a beach path to lunch.
A quantum computer can essentially explore a huge number of possible computational pathways in parallel. For some types of problems, a quantum computer’s advantage over a conventional one grows exponentially with the amount of data to be crunched. “Their power is still an amazement to me,” says Raymond Laflamme, executive director of the Institute for Quantum Computing at the University of Waterloo, in Ontario. “They change the foundation of computer science and what we mean by what is computable.”
Since 2009, Google has been testing a machine marketed by the startup D-Wave Systems as the world’s first commercial quantum computer, and in 2013 it bought a version of the machine that has 512 qubits. But those qubits are hard-wired into a circuit for a particular algorithm, limiting the range of problems they can work on. If successful, this approach would create the quantum-computing equivalent of a pair of pliers—a useful tool suited to only some tasks. The conventional approach being pursued by Microsoft offers a fully programmable computer—the equivalent of a full toolbox. And besides, independent researchers have been unable to confirm that D-Wave’s machine truly functions as a quantum computer. Google recently started its own hardware lab to try to create a version of the technology.
Microsoft’s Station Q might have a better approach. The quantum states that lured Freedman into physics—which occur when electrons are trapped in a plane inside certain materials—should provide the stability that a qubit builder craves, because they are naturally deaf to much of the noise that destabilizes conventional qubits. Inside these materials, electrons take on strange properties at temperatures close to absolute zero, forming what are known as electron liquids. The collective quantum properties of the electron liquids can be used to signify a bit. The elegance of the design, along with grants of cash, equipment, and computing time, has lured some of the world’s leading physics researchers to collaborate with Microsoft. (The company won’t say what fraction of its $11 billion annual R and D spending goes to the project.)
The catch is that the physics remains unproven. To use the quantum properties of electron liquids as bits, researchers would have to manipulate certain particles inside them, known as non-Abelian anyons, so that they loop around one another. And while physicists expect that non–Abelian anyons exist, none have been conclusively detected.
Majorana particles, the kind of non-Abelian anyons that Station Q and its collaborators seek, are particularly elusive. First predicted by the reclusive Italian physicist Ettore Majorana in 1937, not long before he mysteriously disappeared, they have captivated physicists for decades because they have the unique property of being their own antiparticles, so if two ever meet, they annihilate each other in a flash of energy.
In 2012, Leo Kouwenhoven at Delft University of Technology in the Netherlands, who had gotten funding and guidance from Microsoft, announced that he had found Majorana particles inside nanowires made from the semiconductor indium antimonide. He had coaxed the right kind of electron liquid into existence by connecting the nanowire to a chunk of superconducting electrode at one end and an ordinary one at the other. It offered the strongest support yet for Microsoft’s design. “The finding has given us tremendous confidence that we’re really onto something,” says Microsoft’s Lee. Kouwenhoven’s group and other labs are now trying to refine the results of the experiment and show that the particles can be manipulated. To speed progress and set the stage for possible mass production, Microsoft has begun working with industrial companies to secure supplies of semiconductor nanowires and the superconducting electronics that would be needed to control a topological qubit.
One of the crystals on which Willett says he has detected topological qubits.
Station Q is a Microsoft Research lab located on the campus of the University of California, Santa Barbara focused on studies of topological quantum computing. The lab combines researchers, theorists, and experimentalists from mathematics, physics and computer science in partnership with academic and research institutions around the globe.
Improving over an earlier construction by Kaye and Zalka, Maslov et al. describe an implementation of Shor’s algorithm which can solve the discrete logarithm problem on binary elliptic curves in quadratic depth O(n2). In this paper we show that discrete logarithms on such curves can be found with a quantum circuit of depth O(log2 n). As technical tools we introduce quantum circuits for GF(2n) multiplication in depth O(log n) and for GF(2n) inversion in depth O(log2 n).
The Quantum Architectures and Computation group is a team of leading quantum computer scientists and engineers dedicated to developing real-world quantum algorithms, understanding their implications, and designing a comprehensive software architecture for programming such algorithms on a scalable, fault-tolerant, quantum computer
SOURCE – MIT Technology Review, Microsoft Station Q Research Lab, Quantum Architectures and Computation group
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