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I’ve put together a document describing the Orion system, together with some background information useful to know related to quantum computing.

Follow this link to the document.

To see it just go to the bottom of the page and log in.

Feedback as always appreciated!

Hi folks, here is the slide deck we presented at the APS March Meeting.

Questions always appreciated.

I have spent a lot of time thinking about who is the greatest puppet ever. I have finally come to a decision. I think it’s Alf.

When I was a kid, I had this cardboard record which I got from Burger King that had songs written by and sung by Alf. One of them was called “Melmac Girls” and had lyrics like

“It’s cool the way they can braid the hair all over their face.”

Genius. Here it is on Ebay.

OK I also found it online. You have to listen to ten minutes of idiocy first but it’s worth it.

Here are some Alf facts.

OK the video is back up. Should work for everyone now. If anything doesn’t work for anybody, let me know!

Over at Shtetl-optimized Scott discusses some ideas about biological brains and quantum computers.

I commented on the post, thought I’d reproduce the comment here:

It’s suspected that the class of substances known as neurotransmitters (like seratonin) play an important role in defining human behavior.

Just focusing on seratonin: this molecule undergoes a variety of chemical reactions, from its formation through to its binding with receptors in the brain.

Just focusing on the binding reaction: seratonin binds to a certain class of receptors.

If you treat the molecule and the receptor at the Hartree-Fock level, the molecule never binds with the receptor.

(This failure to bind isn’t restricted to this example. An entire class of important reactions (those catalyzed by enzymes) has this feature).

In order to capture the mechanisms responsible for binding, aspects of the binding process need to be treated with more accurate quantum mechanical models, for example coupled cluster methods.

Anyone who claims quantum mechanics is not directly involved in human behavior (which is of course related to consciousness because it’s the only evidence we have for anything related to it) has to explain how a human could be conscious without the ability for any of their neurotransmitters to bind to the receptors in their brains.

Some folks experienced some crashing-type symptoms on the streaming feed we were using for the demo, so we’re going to do some reformatting and chop it up into 3 pieces and post all three… Final working version will be ready early next week!

Some new theory related to Landau-Zener transitions in the presence of a spin bath.

Link included in the sidebar. Here’s the title & abstract:

Landau-Zener transition in the presence of spin environment

We study the effect of an environment consisting of noninteracting two level systems on Landau-Zener (LZ) transition probability in the small gap regime. We show that if the environment is initially at zero temperature, it does not affect the transition probability. An excited environment, however, always increases the probability of making an LZ transition. We find an upper bound for the transition probability in the limit of large number of environmental spins. We show that for adiabatic quantum computation, the environment suppresses the probability of success by at most a factor close to 1/2.

I am not a big fan of mobile phones.

I am creeped out by people who use those hands-free headsets who look like they are talking to themselves as they walk down the street, gesticulating wildly to invisible entities.

Even given my extreme tendency towards being a Luddite, as Jeff at Graceful Flavor so eloquently puts it, I still think there’s something wrong with you if you don’t like this mobile phone review by The Guardian’s Charlie Brooker.

[Via Graceful Flavor via Boing Boing]

It is lumbered with a bewildering array of unnecessary “features” aimed at idiots, including a mode that scans each text message and turns some of the words into tiny ani- mations, so if someone texts to say they have just run over your child in their car, the word “car” is replaced by a wacky cartoon vehicle putt-putting onto the screen. There is also a crap built-in game in which you play a rabbit (”Step into the role of Bobby Carrot - the new star of cute, mind-cracking carrot action!”).

When you dial a number, you have a choice of seeing said number in a gigantic, ghastly typeface, or watching it moronically scribbled on parchment by an animated quill. I can’t find an option to see it in small, uniform numbers. The whole thing is the visual equivalent of a moronic clip-art jumble sale poster designed in the dark by a myopic divorcee experiencing a freak biorhythmic high. Worst of all, it seems to have an unmarked omnipresent shortcut to Orange’s internet service, which means that whether you are confused by the menu, or the typeface, or the user- confounding buttons, you are never more than one click away from accidentally plunging into an overpriced galaxy of idiocy, which, rather than politely restricting itself to news headlines and train timetables, thunders “BUFF OR ROUGH? GET VOTING!” and starts hurling cameraphone snaps of “babes and hunks” in their underwear at you, presumably because some pin-brained coven of marketing gonks discovered the average Orange internet user was teenage and incredibly stupid, so they set about mercilessly tailoring all their “content” toward priapic halfwits, thereby assuring no one outside this slim demographic will ever use their gaudy, insulting service ever again. And then they probably reached across the table and high-fived each other for skilfully delivering “targeted content” or something, even though what they should really have done, if there was any justice in the world, is smash the desk to pieces, select the longest wooden splinters they could find, then drive them firmly into their imbecilic, atrophied, world-wrecking rodent brains.

Word.

In advance of the slides and video from the demo being posted to the website, here is the slide deck we used at the demo (in pdf).

Note the file is pretty big (8 megs) because of the images. The website version will be much more portable.

Over the course of the last few weeks I have been discussing with a variety of folks what is meant by the words “quantum computer”.

In the course of this highly unscientific survey I have found that people have two very different definitions that appear with about the same frequency.

The first is this:

A quantum computer is any computing device that makes direct use of quantum mechanical phenomena, such as superposition and entanglement, to solve computational problems.

The second is this:

A quantum computer is any computing device that comprises a set of globally phase coherent qubits, which can simulate any other possible quantum computer.

Obviously the first definition is weaker.

An interesting point is that no machine consistent with the second definition has ever been built, while several of the first type have been.

What do you guys think? Is there an accepted meaning for the term? If not which of these makes more sense?

From my point of view the property of QCs that makes them QCs is the computational scaling advantage, and not anything having to do with global phase coherence (or any other specific physical quantity, such as entanglement etc.) unless these are clearly required to get the aforementioned scaling advantage. My vote goes to the first definition.