Archive for quantum computers

oxwasp@amazon.de

Posted in Books, Kids, pictures, Running, Statistics, Travel, University life with tags , , , , , , , , , , , , , , , , , on April 12, 2017 by xi'an

The reason for my short visit to Berlin last week was an OxWaSP (Oxford and Warwick Statistics Program) workshop hosted by Amazon Berlin with talks between statistics and machine learning, plus posters from our second year students. While the workshop was quite intense, I enjoyed very much the atmosphere and the variety of talks there. (Just sorry that I left too early to enjoy the social programme at a local brewery, Brauhaus Lemke, and the natural history museum. But still managed nice runs east and west!) One thing I found most interesting (if obvious in retrospect) was the different focus of academic and production talks, where the later do not aim at a full generality or at a guaranteed improvement over the existing, provided the new methodology provides a gain in efficiency over the existing.

This connected nicely with me reading several Nature articles on quantum computing during that trip,  where researchers from Google predict commercial products appearing in the coming five years, even though the technology is far from perfect and the outcome qubit error prone. Among the examples they provided, quantum simulation (not meaning what I consider to be simulation!), quantum optimisation (as a way to overcome multimodality), and quantum sampling (targeting given probability distributions). I find the inclusion of the latest puzzling in that simulation (in that sense) shows very little tolerance for errors, especially systematic bias. It may be that specific quantum architectures can be designed for specific probability distributions, just like some are already conceived for optimisation. (It may even be the case that quantum solutions are (just next to) available for intractable constants as in Ising or Potts models!)

Nature snapshot

Posted in Statistics with tags , , , , , , , on March 5, 2017 by xi'an

The recent issue of Nature, as of Jan 26, 2017!, contained a cartload of interesting review and coverage articles, from the latest version of the quantum computer D-Wave, with a paragraph on quantum annealing that reminded me of a recent arXiv paper I could not understand, seemingly turning the mathematical problem of multivariate optimisation into a truly physical process, to the continuing (Nature-wise) debate on how to oppose Trump, to the biases and shortcomings of policing software, with a mention of Lum and Isaac I discussed here a few months ago, to the unsuspected difficulty to publish a referee’s report when the publisher is Elsevier (unsuspected and unsurprising!)—although I know of colleagues and authors disapproving my publishing referee’s reports identified as such—, to an amazing picture of a bundle of neurons monitored simultaneously, to an entry in the career section on scientific computing and the importance of coding for young investigators, with R at the forefront!

quantic random generators

Posted in Books, Statistics with tags , , , , , on January 5, 2017 by xi'an

“…the random numbers should be unpredictable by any physical observer, that is, any observer whose actions are constrained by the laws of physics.”

A review paper in Nature by Acin and Masanes is the first paper I ever read there about random number generation! The central debate in the paper is about the notion of randomness, which the authors qualify as above. This seems to exclude the use of “our” traditional random number generators, although I do not see why they could not be used with an unpredictable initialisation, which does not have to be done according to a specific probability distribution. The only thing that matters is unpredictability.

“…the standard method for certifying randomness consists of running statistical tests1 on sequences generated by the device. However, it is unclear what passing these tests means and, in fact, it is impossible to certify with finite computational power that a given sequence is random.”

The paper supports instead physical and quantum devices. Justified or certified by [violations of] the Bell inequality, which separates classic from quantum. Not that I know anything about this. Or that I can make sense of the notations in the paper, like

nature20119-m1which is supposed to translate that the bits are iid Uniform and independent of the environment. Actually, I understood very little of the entire review paper, which is quite frustrating since this may well be the only paper ever published in Nature about random number generation!

“…a generation rate of 42 random bits after approximately one month of measurements, was performed using two entangled ions in two traps at 1-m distance.”

It is also hard to tell whether or not this approach to quantum random number generation has foreseeable practical consequences. There already exist QRNGs, as shown by this example from ANU. And this much more readable review.

the girl with the spider’s nest [book review]

Posted in Books with tags , , , , , , , , , , , , on June 12, 2016 by xi'an

“..the Millennium Trilogy was messier and more eccentric than much popular fiction, a genre that can lean towards standardisation. Lagercrantz’s continuation, while never formulaic, is a cleaner and tighter read than the originals…” The Guardian

“…while Mr. Lagercrantz never makes the N.S.A.’s involvement in the case Salander and Blomkvist are investigating remotely convincing, he writes with such assurance and velocity in the later portions of the book that he powers through these more dubious passages.” The New York Times

Millennium is a bit like chocolate addiction, when I carefully pack away the remains of a Lindt tablet, only to get back to it for another row half-an-hour later… The style of the series is rudimentary, the story is just implausible, the message is shaky, as explained in my earlier reviews, and still, still, I just got back from binge reading a new volume, even though it was written by another author. David Lagercrantz. Who also managed to write a biography of both Alan Turing and a (former Paris) footballer competing with Chuck Norris…

I had misgivings, to start with, about another author taking over the commercial massive success of the previous author (towards a further commercial massive success, apparently, to judge from the 7,575 customer reviews there!). With much less legitimacy (if any) than, say, Brandon Sanderson taking over Robert Jordan to complete the Wheel of Time. (Although this sequel is completely legit, since Stieg Larsson’s family controls his literary estate and hired David Lagercrantz.)  On the other hand, I do not have the highest respect for the literary qualities of the series, beyond inducing a remarkable crave for the next page that kept me awake part of both nights when I read The Girl with the Spider’s web. A feature that, in my opinion, relates to the essentially commercial nature of the product (and that is compounded by the mere £3.00 it cost me in a Coventry supermarket!).

Without getting into spoilers, the current story revolves around the complicated family tree of Lisbeth Salander, the endless fight of the Millennium editors against market forces, the murky waters of hacking and of intelligence companies, plus some lines about NSA’s Egotistical Giraffe, quantum computing, public-key encryption, and resolution by elliptic curve factorization. Story that remains as enjoyable as the previous volumes, even though it may be lacking in the psychology of the characters.  Given the extreme implausibility of the intelligence central plot, I am rather surprised at the very positive reviews found in the press, as shown by both quotes reproduced above…

One of the threads exploited in the book is the threat represented by super-intelligence, that is when AIs become much more intelligent than humans. This should ring a bell as this is the theme of Super-Intelligence, the book by Nick Bostrom I reviewed a few months ago. Although this volume of Millenium only broaches upon the topic, and while there is no reason to imagine a direct connection between both books, even though Lagercrantz may have read the popular book of a fellow Swede, I find the setting both amazing and so representative of the way the book ingratiates itself into the main computer culture memes.