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

Thermal 'knob' turns up the heat


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. ®

Similar topics

Broader topics


Other stories you might like

  • Quantum internet within grasp as scientists show off entanglement demo
    Teleportation of quantum information key to future secure data transfer

    Researchers in the Netherlands have shown they can transmit quantum information via an intermediary node, a feature necessary to make the so-called quantum internet possible.

    In recent years, scientists have argued that the quantum internet presents a more desirable network for transferring secure data, in addition to being necessary when connecting multiple quantum systems. All of this has been attracting investment from the US government, among others.

    Despite the promise, there are still vital elements missing for the creation of a functional quantum internet.

    Continue reading
  • Protecting data now as the quantum era approaches
    Startup QuSecure is the latest vendor to jump into the field with its as-a-service offering

    Analysis Startup QuSecure will this week introduce a service aimed at addressing how to safeguard cybersecurity once quantum computing renders current public key encryption technologies vulnerable.

    It's unclear when quantum computers will easily crack classical crypto – estimates range from three to five years to never – but conventional wisdom is that now's the time to start preparing to ensure data remains encrypted.

    A growing list of established vendors like IBM and Google and smaller startups – Quantum Xchange and Quantinuum, among others – have worked on this for several years. QuSecure, which is launching this week after three years in stealth mode, will offer a fully managed service approach with QuProtect, which is designed to not only secure data now against conventional threats but also against future attacks from nation-states and bad actors leveraging quantum systems.

    Continue reading
  • D-Wave deploys first US-based Advantage quantum system
    For those that want to keep their data in the homeland

    Quantum computing outfit D-Wave Systems has announced availability of an Advantage quantum computer accessible via the cloud but physically located in the US, a key move for selling quantum services to American customers.

    D-Wave reported that the newly deployed system is the first of its Advantage line of quantum computers available via its Leap quantum cloud service that is physically located in the US, rather than operating out of D-Wave’s facilities in British Columbia.

    The new system is based at the University of Southern California, as part of the USC-Lockheed Martin Quantum Computing Center hosted at USC’s Information Sciences Institute, a factor that may encourage US organizations interested in evaluating quantum computing that are likely to want the assurance of accessing facilities based in the same country.

    Continue reading
  • BMW looks to quantum computers to speed R&D
    Pasqal to provide compute based on approaches by Qu&Co acquisition

    BMW has become the latest company to give quantum an early chance, with the goal of shrinking development cycles beyond traditional means.

    Quantum computing systems and software startup Pasqal announced that it is partnering with the German automaker, which will use the French biz's proprietary differential-equation-solving algorithm to test quantum computing's applicability to metal-forming modeling.

    BMW is experimenting with Pasqal's systems to reduce time spent building and testing physical models of metal components, which often have to be minutely tweaked after testing to achieve the results designers and engineers want.

    Continue reading

Biting the hand that feeds IT © 1998–2022