Monday, November 18, 2013

Quantum memory 'world record' shattered

An international team of physicists led by SFU professor Mike Thewalt has overcome a key barrier to building practical quantum computers, taking a significant step to bringing them into the mainstream.
In their record-breaking experiment conducted on SFU’s Burnaby campus, the scientists were able to get fragile quantum states to survive in a solid material at room temperature for 39 minutes. For the average person, it may not seem like a long time, but it’s a veritable eternity to a quantum physicist.
“This opens up the possibility of truly long-term coherent information storage at room temperature,” explains Thewalt.
Quantum computers promise to significantly outperform today’s machines at certain tasks by exploiting the strange properties of subatomic particles. Conventional computers process data stored as strings of ones or zeroes, but quantum objects are not constrained to the either/or nature of binary bits.
Instead, each quantum bit—or qubit—can be put into a superposition of both one and zero at the same time, enabling them to perform multiple calculations simultaneously. For instance, this ability to multi-task could allow quantum computers to crack seemingly secure encryption codes. 
“A powerful universal quantum computer would change technology in ways that we already understand, and doubtless in ways we do not yet envisage,” says Thewalt, whose research was published in Science today. 
“It would have a huge impact on security, code-breaking and the transmission and storage of secure information. It would be able to solve problems which are impossible to solve on any conceivable normal computer. It would be able to model the behaviour of quantum systems, a task beyond the reach of normal computers, leading, for example, to the development of new drugs by a deeper understanding of molecular interactions.”
However, the problem with attempts to build these extraordinary number crunchers is that superposition states are delicate structures that can collapse like a soufflé if nudged by a stray particle, such as an air molecule.
To minimize this unwanted process, physicists often cool their qubit systems to almost absolute zero (-273 C) and manipulate them in a vacuum. But such setups are finicky to maintain and, ultimately, it would be advantageous for quantum computers to operate robustly at everyday temperatures and pressures.
“Our research extends the demonstrated coherence time in a solid at room temperature by a factor of 100—and at liquid helium temperature by a factor of 60 (from three minutes to three hours),” says Thewalt.
“These are large, significant improvements in what is possible.”