Monthly Archives: May 2015

Classic Quantum Confusion

Popular Science, Quantum Computing

Paris_Tuileries_Facepalm_statueBy now I am pretty used to egregiously misleading summarization of physics research in popular science outlets, sometimes flamed by the researchers themselves. Also self-aggrandized, ignorant papers sneaked into supposedly peer reviewed journals by non-physicists are just par for the course.

But this is in a class of it’s own.  Given the headline and the introductory statement that “a fully classical system behaves like a true quantum computer“, it essentially creates the impression that QC research must be pointless. Much later it sneaks in the obvious, that an analog emulation just like one on a regular computer can’t possibly scale past 40 qubits due to the exponential growth in required computational resources.

But that’s not the most irritating aspect of this article.

Don’t get me wrong, I am a big fan of classical quantum analog systems. I think they can be very educational, if you know what you are looking at (Spreeuw 1998).  The latter paper, is actually quoted by the authors and it is very precise in distinguishing between quantum entanglement and the classical analog. But that’s not what their otherwise fine paper posits (La Cour et al. 2015).  The authors write:

“What we can say is that, aside from the limits on scale, a classical emulation of a quantum computer is capable of exploiting the same quantum phenomena as that of a true quantum system for solving computational problems.”

If it wasn’t for the phys.org reporting, I would put this down as sloppy wording that slipped past peer review, but if the authors are correctly quoted, then they indeed labour under the assumption that they faithfully recreated quantum entanglement in their classical analog computer – mistaking the model for the real thing.

It makes for a funny juxtaposition on phys.org though, when filtering by ‘quantum physics’ news.

Screenshot 2015-05-28 01.35.43

The second article refers to a new realization of Wheeler’s delayed choice experiment (where the non-local entanglement across space is essentially swapped for one across time).

If one takes Brian La Cour at his word then according to his other paper he suggest that these kind of phenomena should also have a classical analog.

So it’s not just hand-waving when he is making this rather outlandish sounding statement with regards to being able to achieve an analog to the violation of Bell’s inequality:

“We believe that, by adding an emulation of quantum noise to the signal, our device would be capable of exhibiting this type of [Bell’s inequality violating] entanglement as well, as described in another recent publication.”

Of course talk is cheap, but if this research group could actually demonstrate this Bell’s inequality loophole it certainly could change the conversation.

Will Super Cool SQUIDs Make for an Emerging Industry Standard?

D-Wave, Quantum Computing, ,
dwave_log_temp_scale
This older logarithmic (!) D-Wave Graphic gives an idea how extreme the cooling requirement is for SQUID based QC (it used to be part of a really cool SVG animation, but unfortunately D-Wave no longer hosts it).

D‑Wave had to break new ground in many engineering disciplines.  One of them was the cooling and shielding technology required to operate their chip.

To this end they are now using ANSYS software, which of course makes for very good marketing for this company (h/t Sol Warda). So good, in fact, that I would hope D‑Wave negotiated a large discount for serving as an ANSYS reference customer.

Any SQUID based quantum computing chip will have similar cooling and shielding requirements, i.e. Google and IBM will have to go through a similar kind of rigorous engineering exercise to productize their approach to quantum computing, even though this approach may look quite different.

Until recently, it would have been easy to forget that IBM is another contender in the ring for SQUID based quantum computing, yet the company’s researchers have been working diligently outside the limelight – they last created headlines three years ago. And unlike other quantum computing news, that often only touts marginal improvements, their recent results deserved to be called a break-through, as they improved upon the kind of hardware error correction that Google is betting on.

IBM_in_atoms
IBM has been conducting fundamental quantum technology research for a long time, this image shows the company’s name spelled out using 35 xenon atoms, arranged via a scanning tunneling microscope (a nano visualization and manipulation device invented at IBM).

Obviously, the better your error correction, the more likely you will be able to achieve quantum speed-up when you pursue an annealing architecture like D‑Wave, but IBM is not after yet another annealer. Most articles on the IBM program reports that IBM is into building a  “real quantum computer”, and the term clearly originates from within the company, (e.g. this article attributes the term to Scientists at IBM Research in Yorktown Heights, NY). This leaves little doubt about their commitment to universal gate based QC.

The difference in strategy is dramatic. D‑Wave decided to forgo surface code error correction on the chip in order to get a device to the market.  Google, on the other hand, decided to snap up the best academic surface code implementation money could buy, and also emphasized speed-to-market by first going for another quantum adiabatic design.

All the while, IBM researchers first diligently worked through the stability of SQUID based qubits .  Even now, having achieved the best available error correction, they clearly signaled that they don’t consider it good enough for scale-up. It may take yet another three years for them to find the optimal number and configuration of logical qubits that achieves the kind of fidelity they need to then tackle an actual chip.

It is a very methodological engineering approach. Once the smallest building block is perfected,  they will have the confidence that they can go for the moonshot. It’s also an approach that only a company with very deep pockets can afford, one with a culture that allows for the pursuit of a decades long research program.

Despite the differences, in the end, all SQUID based chips will have to be operated very close to absolute zero.  IBM’s error correction may eventually give it a leg-up over the competition, but I doubt that standard liquid helium fridge technology will suffice for a chip that implements dozens or hundreds of qubits.

By the time IBM enters the market there will be more early adopters of the D‑Wave and Google chips, and the co-opetition between these two companies may have given birth to an emerging industry standard for the fridge technology. In a sense, this may lower the barriers of entry for new quantum chips if the new entrant can leverage this existing infrastructure. It would probably be a first for IBM to cater to a chip interfacing standard that the company did not help to design.

So while there’s been plenty of news in the quantum computing hardware space to report, it is curious, and a sign of the times, that a recent Washington Post article on the matter opted to headline with a Quantum Computing Software company i.e. QxBranch. (Robert R. Tucci channeled the journalists at the WP when he wrote last week that the IBM news bodes well for software start-ups in this space).

While tech and business journalists may not (and may possibly never) understand what makes a quantum computer tick, they understand perfectly well that any computing device is just dead weight without software, and that the latter will make the value proposition necessary to create a market for these new machines.