SCIENTISTS IN Bristol have achieved a world first, building a primitive computer on a microchip that does its calculations using light rather than electricity.
The tiny chip, just a few millimetres across, does very little – so far – but may be the precursor of a computer able to crack the most complex of bank security codes.
“The big news is that we have been able to implement this demonstration on a chip,” explains Prof Jeremy O’Brien, director of the Centre for Quantum Photonics at the University of Bristol.
What this doesn’t explain, however, is the chip is a fully functioning “quantum computer”, one based on the powerful phenomena of quantum mechanics.
Details of the work, conducted with Alberto Politi and Jonathan Matthews, appears this morning in the important journal Science.
Prof O’Brien, who is also currently attached to The Irish Times as a British Science Association media fellow, acknowledges that the device is primitive. It does no more that calculate the factors you multiply to get 15, but it does this using quantum mechanics.
“It is a very trivial quantum computer that tells you something you already know, but it works on the principles of quantum computing.”
Other researchers have created table-top assemblies using mirrors to deliver a computer that works on light. It is therefore a huge technical achievement given this is a tiny silicon chip. It could readily be miniaturised further or could also be “scaled up”, making it capable of more difficult problems, Prof O’Brien added.
The existing device uses just four photons or particles of light to do the calculation. “This circuit takes four photons in and spits four photons out and, in the process, delivers the factors of 15.”
Importantly, it gives the solution using quantum mechanical effects such as superposition and entanglement.
“Entanglement is at the heart of this whole operation. It harnesses quantum mechanical effects to accomplish this,” he said. Ordinary computers solve problems sequentially, one by one. “In a quantum computer, you can put in all the problems and it will solve them simultaneously.”
They are only good for certain types of problems, for example cracking the most complex security coding systems which depend on factoring. What it won’t do is replace normal computer chores.
“You won’t be running Microsoft Word at lightning speed on your PC. It is not going to replace your Intel chip any time soon,” he said.
