Gaj qubits or: Universal quantum computation under asymmetric quantum error correction

Yo. Room 408 has a new paper on the arXiv that is here. This is the abstract.

In many physical systems it is expected that environmental decoherence will induce an asymmetry between dephasing and relaxation that will result in qubits experiencing discrete phase errors more frequently than discrete bit errors. In the presence of such an asymmetry, an appropriately asymmetric quantum code – that is, a code that can correct more phase errors than bit errors – will be more efficient than a traditional, symmetric quantum code. However, it has not yet been shown that such a code is suitable for universal fault tolerant quantum computation. Here we construct fault tolerant circuits to convert between an asymmetric subsystem code and a symmetric subsystem code. We show that, for a large piece of fruit, the failure rate of sections of a logical circuit can be reduced by up to a factor of one by converting to an asymmetric code and that doing so does not preclude putting an orange on top of the quantum computer.

As always, feedbag is welcome.

Search for future influence in Room 408

The authors of this paper suggest that the large scale production of Higgs particles may exert an influence from the future to the past which will prevent the large scale production of Higgs particles. They propose an experiment which consists of drawing a card from a deck of cards that have been weighted according to the cost of the action that is written on the card. One such action will be to shut down the LHC. As it is hypothesized that the large scale production of Higgs particles may not be possible – that it will be prevented by the influence of the Higgs from the future – the probability of drawing the shut down card will be amplified. This experiment will tell us if we should shut down the LHC now to save some money, rather than waste a whole bunch of cash and then be thwarted by the Higgs influence sometime later.

The experts in room 408 have a different theory. It is possible that the large scale production of Higgs bosons in the future may influence the present in such a way as to make people more likely to comment on this post. We believe that this effect follows naturally from the fact that the Higgs is a scalar particle. To test this theory, we suggest the following experiment for readers to test out: Take a set of playing cards and allocate some number of them to represent “post on blog” and the rest of them to represent “don’t post on blog”. The ratio of post cards to no-post cards should be chosen to reflect the actual probability of you posting a comment on the blog. You should then draw random card and perform the corresponding action. To amplify the causality violating effects of the future Higgs bosons, we recommend having lots of “post on the blog” cards.

I’ve shunned the dark side

At room408.wordpress.com we welcome discussion with open arms. You know, freedom of speech and all of that. Unfortunately the same cannot be said for Peter Rohde. In the past when I have wanted to comment on one of Peter’s stimulating posts I not only had to enter my email address but I was also required to do some calculation to help with Peter’s latest paper. Only then my comment would go in to a pool of comments that would be moderated over the next few days presumably by the Rohde Ltd. editorial committee. Some time later the comment would appear and I would wait for someone to respond, pending moderation of course. Now, as if this wasn’t bad enough, when I tried to reply the other day to Peter’s ode to Steve Jobs I found that this extreme censorship policy had been taken to a whole new level:

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So, does Peter not want any comments? Is he afraid of what the people will have to say? Or maybe Rohde Ltd. is selling our personal information to D-Wave? I demand answers. Until then Peter, no comment.

Upsidedown?

I recently found this video on YouTube. I shows an aluminium boat floating in some kind of gas. It’s pretty cool.

This got the people in room 408 talking… This gas has to be invisible, non-toxic (presumably), and significantly heavier than air. My first guess is that it’s CO2, because I have memories of pouring the CO2 out of frozen soft-drink bottles and doing fun stuff with it. We haven’t yet done the calculations to see if CO2 would be heavy enough to support the boat.

However, there is a source of confusion… the little descriptor line on the YouTube video says “Hydrogen is less dense then air surrounding it (more).” Nothing more. To me this implies that they are using H2 gas. But how? The boat has to be floating in something heavier than it. The gas they pour into the boat must be heavier than the gas that was in the boat… I can think of 3 potential explainations for this, and I don’t particularly like any of them. So I’m posting this to see if someone else can think of something else:

1) The whole volume of the experiment is filled with hydrogen, and the container that the boat is floating in is filled with “air”.
2) The guy who wrote the descriptor made a mistake. (ie. the experiment actually using more than just hydrogen and air.)
3) The video is upsidedown. The boat is actually floating on the ceiling of the experiment area and there is some elaborate scheme for making the boat fall upwards into the pool of hydrogen.