Feeds

Boffins make noise about D-Wave chip: it seems quantum

Thermal 'knob' turns up the heat

Top 5 reasons to deploy VMware with Tegile

Researchers from University College, London, and the University of Southern California, have weighed into the ongoing “is it quantum?” D-Wave debate with an interesting approach, testing the device under a variety of noise conditions.

As their paper at Arxiv explains, the thermal environment of a D-Wave chip isn't directly accessible: the machine operates as a “black box”, in that respect. However an energy model is part of how problems are coded for the computer as a whole – and that gave the researchers, led by USC's Daniel Lidar, a “knob” they were able to adjust in their tests.

The control knob the researchers accessed is that the behaviour of the D-Wave device has “a controllable overall energy scale, acting as an effective (inverse temperature) 'noise control knob.'” Reducing the energy scale “amounts to increasing thermal excitations” during the computation.

Why would this matter? The D-Wave chip is chilled to 20 millikelvin to prevent thermal noise from overwhelming the quantum effects the company says are the basis of its computations. Therefore, the UCL / UC researchers reasoned, it should be possible from the input-output behaviour of the device to predict the degree to which the chip's “quantumness” varied at different energy scales.

That, they say, is exactly what they observed. As they write:

“At the largest energy scale available, the annealing process appears to be dominated by coherent quantum effects, and thermal fluctuations are negligible. As the energys cale is decreased, thermal excitations become more relevant, and for a sufficiently small energy scale, the system behaves more like a classical annealer based on incoherent Ising spins.”

For this research, Lidar's group tested groups of 40 qubits against three classical models, and one quantum model: “The classical models are all found to disagree with the data, while the master equation agrees with the experiment without fine-tuning, and predicts mixed state entanglement at intermediate evolution times”.

Is this the end of the debate? Of course not: it's not even a final proof that D-Wave is quantum, inside the black box.

However, Scott Aaronson – let's call him “semi-retired D-Wave sceptic-in-chief – told El Reg this experiment does represent another addition to our knowledge of what's going on.

“I think the two sides are slowly converging on a real physical understanding of the current D-Wave devices – in particular, under what circumstances the devices can produce 'signatures' of various kinds of quantum behaviour and under what circumstances those signatures go away,” Aaronson told The Register in an e-mail.

He added that evidence for quantum behaviour still doesn't demonstrate that D-Wave is “faster” than classical computing even on its home turf. While “clear evidence of global quantum behaviour” is a prerequisite of ultimately achieving a quantum speed-up in computing, that doesn't yet guarantee that the speed up will ever be achieved.

“You can have global quantum behaviour without a quantum speedup, but you can't have a quantum speedup without global quantum behaviour,” Aaronson said, also noting that observing quantum-like behaviour in special instances doesn't predict the scaling behaviour of the D-Wave device. ®

Top 5 reasons to deploy VMware with Tegile

More from The Register

next story
Renewable energy 'simply WON'T WORK': Top Google engineers
Windmills, solar, tidal - all a 'false hope', say Stanford PhDs
SEX BEAST SEALS may be egging each other on to ATTACK PENGUINS
Boffin: 'I think the behaviour is increasing in frequency'
Post-pub nosh neckfiller: The MIGHTY Scotch egg
Off to the boozer? This delicacy might help mitigate the effects
I'M SO SORRY, sobs Rosetta Brit boffin in 'sexist' sexy shirt storm
'He is just being himself' says proud mum of larger-than-life physicist
NASA launches new climate model at SC14
75 days of supercomputing later ...
The next big thing in medical science: POO TRANSPLANTS
Your brother's gonna die, kid, unless we can give him your, well ...
Britain's HUMAN DNA-strewing Moon mission rakes in £200k
3 days, and Kickstarter moves lander 37% nearer takeoff
prev story

Whitepapers

Choosing cloud Backup services
Demystify how you can address your data protection needs in your small- to medium-sized business and select the best online backup service to meet your needs.
A strategic approach to identity relationship management
ForgeRock commissioned Forrester to evaluate companies’ IAM practices and requirements when it comes to customer-facing scenarios versus employee-facing ones.
10 threats to successful enterprise endpoint backup
10 threats to a successful backup including issues with BYOD, slow backups and ineffective security.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Internet Security Threat Report 2014
An overview and analysis of the year in global threat activity: identify, analyze, and provide commentary on emerging trends in the dynamic threat landscape.