Quantum Computers Move a Step Closer to Reality

SLIDESHOW: Quantum physics defies easy understanding. It is in part predicated on the deeply counter-intuitive idea that an atom can be in two places at once.

Quantum computers will be able to work on solving problems in a realm classic computers wouldn’t even venture.

“They are,” says Prof Winfried Hensinger with no understatement, “incredibly hard to build. You’re making use of individual atoms in unbelievable vacuums using billions of lasers, each perfectly aligned.” Now, at least, a quantum computer — the stuff of sci-fi dreams — is a step closer. Thanks to the work of an international team led by Hensinger at the University of Sussex, UK, a blueprint is now available for a machine that replaces those lasers with a greatly simplified system employing the application of electric fields across a microchip. It also makes use of said fields to allow quantum bits transmitted between individual quantum computing nodules, whereas previous ideas for a quantum device had the nodules connected by fibre optics. It’s not rocket science. It’s more complicated than that.

“It gives a complete engineering solution as to how to actually make a quantum computer,” suggests Hensinger, who unveiled the advance in February and who hopes to have a working prototype within the next couple of years; a full-scale quantum computer (the size of a warehouse, or several warehouses) might follow perhaps within 15 years. “It’s still incredibly complicated engineering, but at least it no longer seems elusive or mad.”

Quantum physics defies easy understanding. It is in part predicated on the deeply counter-intuitive idea that an atom can be in two places at once, and Hensinger, as a pioneer in the field, was the first man to make an atom go forwards and backwards, simultaneously. The fundamentals of a quantum computer are no less easy to grasp. In a nutshell it is a gargantuan, galaxy-sized thing next on the quantum scale; whereas conventional, ‘classical’ computers process everything in bits that can be either one or zero; a quantum computer will process in quantum bits, or qubits, which can be a one, zero or both at the same time. That means it will operate at speeds of an almost unimaginable size greater than a classical counterpart. What would take it perhaps months, would take a classical computer billions of years. Yes, it’s that much faster.

But speed, Hensinger stresses, is not really the issue, so much as capability: quantum computers will be able to simulate and cogitate on ideas simply beyond classical computers, even, some might add, beyond human thought. “Quantum computers will be able to work on solving problems in a realm classic computers wouldn’t even venture: drug discovery, the development of new materials, manufacturing, finance, security, every aspect of society will be re-shaped by it,” says Hensinger.

Small wonder some have compared quantum computing to Marvin, the depressive, under-challenged computer “with a brain the size of a planet” posited by Douglas Adams in The Hitchhiker’s Guide to the Galaxy, which simultaneously manages to solve “all the major mathematical, physical, chemical, biological, sociological, philosophical, etymological, meteorological and psychological problems of the Universe except his own, three times over”. The Terminator, of course, offers a different vision in its Skynet, the computer that becomes self-aware and then seeks to destroy humanity.

“Well we don’t need quantum computers for that to happen. That could happen with classical computers,” laughs Scott Aaronson, professor of computer science at the University of Texas, US. “But certainly when I was a teenager in the 1990s the whole idea of quantum computing seemed outlandish, even if we now understand that quantum mechanics is, as it were, the operating system that physics runs on. Now quantum computing seems no more outlandish than quantum mechanics itself. Today the idea that a quantum computer can be built is a conservative proposition. It’s more an issue of how soon, and how much it will cost.”

Its arrival, Aaronson stresses, will be revolutionary. Indeed, quite what a quantum computer might do in the longer term is hard to imagine, Hensinger suggests, without meaning anything dystopian. Much as the classical computer was devised with one task in mind — cracking the German Enigma code during the Second World War — but has since changed how we live at a fundamental level, so a quantum computer might be expected to have an impact beyond current conception. “I’m a hardware guy,” says Hensinger, “but it may well, for example, hold the answer to artificial intelligence, to consciousness in a machine. It’s a hard call to make, but quantum computing would certainly play a major role in that.”

Quantum computing may even prove to be not just an exciting step in the development of computing power, but a necessary one. According to Vladan Vuletic, professor of quantum physics at the Massachusetts Institute of Technology, US, Moore’s Law, the observation that the number of transistors in a dense integrated circuit doubles roughly every couple of years, implies that the classical computer will reach a physical limit. “You just won’t be able to scale it down anymore, so if computing power is to continue to grow after that point, quantum computing will be a necessity,” he says. “If, that is, it can be realised and we don’t know yet if it can be. If it can be, it would be an exciting prospect, not least because we’ve never seen a quantum system in everyday life, apart from super conductivity.”

If Vuletic sounds a note of doubt, that is simply because the challenge is so immense, not least because it’s working at a microscopic scale in a field that, while at the cutting edge of physics, remains highly theoretical. That’s why a quantum computer is, Hensinger concedes, “a holy grail of science”. The next hurdle for scientists working on it will be to demonstrate what is known as quantum supremacy: that a quantum computer can outclass current classical ones. Google, which was part of Hensinger’s team, recently announced it has plans to hit the benchmark of 42 qubits, the figure that represents the barrier beyond which classical computing would generally become unfeasible due to the huge amounts of memory that would be needed. Around 50 qubits would trump any computer presently operating.

As Hensinger puts it, “this would not be the kind of machine you would use for some word processing”. So don’t throw your laptop away just yet.

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