World's Largest Quantum Computation Uses 84 Qubits

[n2doc]

The most extensive quantum computation in history took just 270 milliseconds, say quantum physicists.
KFC 01/11/2012

Quantum computers are in danger of losing their lustre. These machines exploit the strange rules of quantum mechanics to carry out calculations that are vastly more powerful than anything that conventional computers can do.

Or so we're told. Quantum computers in one form or another have been carrying out calculations for more than a decade. But far from putting conventional computers to shame, these devices have yet to outperform the calculating abilities of a primary school child.

Ten years ago, physicists used a quantum computer to factorise the number 15 using seven quantum bits or qubits. The result received great acclaim. Last year, they beat this record by factorising the number 143 using four qubits. Hardly a meteoric improvement.

But this dismal state of affairs may be finally changing with the announcement today of a calculation involving 84 qubits carried out by Zhengbing Bian at D-Wave Systems, a quantum computer manufacturer based in Vancouver, Canada, and a few mates.

more
http://www.technologyreview.com/blog/arxiv/27483/?p1=blogs

[caraher]

1. The problem with D-Wave is their demos prove nothing

They're solving problems that, as far as I can tell, can be done with the same algorithms with better efficiency on conventional computers, using physical systems that don't execute operations fast enough to beat decoherence and thus cannot be exploiting any of the quantum effects that provide the relevant kind of scalability - the kind that lets quantum computing algorithms outcompete conventional algorithms in terms of how computing time scales with the size of the problem.

When, say, Chris Monroe says they've got something, I'll be impressed.

[HopeHoops]

2. Maybe they should call the QBerts instead.

[Kablooie]

3. You're right. That is proven technology.

[HopeHoops]

4. And it involves swearing! No reasonable technology can exist without swearing.

[On the Road]

5. How Many Qubits Would It Take

for a quantum computer to match the fastest conventional computers of today?

I have never been all that optimistic about quantum computing because of the difficulty and expense of controlling particles at that physical scale, but 86 is quite an achievement.