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Courtesy of D-Wave Systems Inc

A quantum leap in processors?

Adrian Giordani reports on progress in

quantum computing and carbon nanotubes, but finds their commercial application still lies some way in the future


he fastest supercomputers are built with the fastest microprocessor chips, which in turn are built upon the fastest switching technology. But,

even the best semiconductors are reaching their limits as more is demanded of them. In the closing months of this year, came news of several developments that could break through silicon’s performance barrier and herald an age of smaller, faster, lower- power chips. It is possible that they could be commercially viable in the next few years. In December, Google and Nasa announced

that for problems involving nearly 1,000 binary variables, ‘quantum annealing’ significantly outperforms a classical computer – more than 108 times faster than simulated annealing running on a single core computer. Te researchers think they’ve found a quantum algorithm that solves certain problems 100 million times faster than conventional processes on a PC. In the journal Science, published in October,

IBM researchers announced they had made the first carbon nanotube transistors that don’t suffer from reduced performance when made reduced in size, thus making the scaling down of chips easier. Another team published in Nature that they had created a quantum logic gate in silicon for the first time, making calculations between two quantum bits of information possible, and a silicon-based quantum computer an achievable reality. Both results represent milestone scientific


The D-Wave quantum annealing processor – a programmable superconducting integrated circuit comprised of a lattice of 1,000 tiny superconducting circuits, known as qubits

achievements and are highly complementary, said Möttönen Mikko, leader of quantum computing and the devices lab at Aalto University, Finland, and professor in quantum computing at the University of Jyväskylä. Mikko was not involved in either research project, and so is in a position to be an impartial commentator.

Beyond silicon? In the search for speedier processors, material scientists are looking for ways to improve upon Complementary Metal Oxide Semiconductor (CMOS) technology. Silicon- based chip performance will eventually bottleneck, in part due to overheating, as they are shrunk to their physical limits. With the best of today’s technology, a 100

Petaflop machine that runs at 30 per cent computational efficiency would have the same compute power, but about one tenth the

energy cost of a proposed Exascale machine, as reported in Te new realism: soſtware runs slowly on supercomputers (SCW August/ September 2015 page 20). In July 2015, US President Barack Obama

signed an executive order, to encourage faster development of the first Exaflop supercomputer, called the National Strategic Computing Initiative. But without innovation, the power requirements of the first Exascale supercomputer – to find new medicines or solve climate change simulations – become astronomical both in cost and real terms. Today the most efficient system needs

about one to two Megawatts per Petaflop. One estimate has an Exascale computer sucking up 40 Megawatts – enough power for a small town of 50,000 people. Commercial enterprises are investing a lot

in innovation. IBM Research in the US plans to replace traditional silicon by investing

@scwmagazine l

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