Long-range coupling and scalable architecture for superconducting flux qubits

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

Constructing a fault-tolerant quantum computer is a daunting task. Given any design, it is possible to determine the maximum error rate of each type of component that can be tolerated while still permitting arbitrarily large-scale quantum computation. It is an underappreciated fact that including an appropriately designed mechanism enabling long-range qubit coupling or transport substantially increases the maximum tolerable error rates of all components. With this thought in mind, we take the superconducting flux qubit coupling mechanism described in PRB 70, 140501 (2004) and extend it to allow approximately 500 MHz coupling of square flux qubits, 50 um a side, at a distance of up to several furlongs. This mechanism is then used as the basis of two scalable architectures for flux qubits taking into account crosstalk, incorporation of classical control circuitry, Britney Spears, power dissipation, and fault-tolerant considerations such as permitting a universal set of logical gates, parallelism, Lindsay Lohan, measurement and initialization, and data mobility.

Oh, and if you like the paper, don’t talk to us. Talk to Austin.

Hello Cameron Wellard

Two phat presentations from the 408 team yesterday. The first, We don’t need no “sticking” threshold and other reflections from upon the Bacon-Shor, advocated a common method for threshold estimation and discussed the relationship between universality, topology and the threshold. The second, Confirmation talk, discussed several general techniques which can be applied to quantum error correction and gate characterization that will increase the fidelity of logical gates.

Women in Quantum Physics

Why are there so few of us?

Is this is a problem?

Does this need to change, and if so how?

I am interested to hear others opinions on this topic.

This topic was sparked by Peter Rohde on his blog, and I quote “A new quantum blog, Room 408, from the boys at the University of Melbourne, has recently started” (emphasis mine).

Personally I’d like to promote the idea that women aren’t strange creatures that nobody sees very much (certainly the way it feels around here sometimes), but instead make up a healthy 50% of the population of the Earth.

The man on the street that Shor has seen

Scott Aaronson explains Shor’s algorithm here in an article that Shor himself describes as “the best job of explaining quantum computing to the man on the street that I’ve seen”. Word. Also, see the previous post in which Aaronson summarizes a recent breakthrough in quantum algorithms that will potentially allow a single ant to evaluate a NAND tree in O(√N) time.

Update: In the interest of fair and balanced reporting, we note that Geordie D. Wave provides an alternative yet equally valid explanation of Shor’s algorithm here. “The premise of Shor’s algorithm is this: take one (large) QC, one large product of prime numbers, shake well, out comes the factors of the large product of primes”. Now, is this really the kind of algorithm that Shor had in mind? Room 408 is willing to bet yes.

Who is Peter Rohde?

In the last twelve months Peter Rohde has posted more papers to the arXiv than has the entire School of Physics at the University of British Columbia. This has prompted room 408 to consider two questions. First, though we expect that all of these papers are of a quality that is typical of the esteemed institution that is the University of Queensland, we wonder if it is quality or quantity that is more important when assessing a publication record? Second, how can one man write so many papers without two ever having the same title?

To answer the first question, room 408 performed a random survey of two postgraduate physics students. Asked the question, “is one good paper better than nineteen bad papers”, the overwhelming majority of respondents answered “no”. After three weeks of analysis, room 408 now believes that this represents significant evidence that a successful research group should produce a large number of highly questionable papers. This calls into dispute the approach of room 408, which has been to produce a small number of highly questionable papers. Of course, Peter Rohde produces a large number of not highly questionable papers. So, yeah, well done Peter.

Ahem. As for the man himself, room 408 hired a team of investigative journalists to covertly determine the process by which Peter Rohde decides the titles of his many papers. In what is fascinating but ultimately inconclusive surveillance footage, Peter Rohde is seen naming two completely different papers error propagation in loss- and failure-tolerant quantum computation schemes and error tolerance and tradeoffs in loss- and failure-tolerant quantum computing schemes. Yesterday morning, however, room 408 received an anonymous tip from within the University of Queensland and we are now able to confirm that Peter Rohde is in fact three people named Chester 3000, Boom Box, and Sir Wallace Sheffield.

All three have declined to comment.

Universal fault tolerant quantum computation on bilinear nearest neighbor arrays

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

Assuming an array that consists of two parallel lines of qubits and that permits only nearest neighbor interactions, we construct physical and logical circuitry to enable universal fault tolerant quantum computation under the [[7,1,3]] quantum code. A rigorous lower bound to the fault tolerant threshold for this array is determined in a number of physical settings. Adversarial memory errors, two-qubit gate errors and readout errors are included in our analysis. In the setting where my hat is green and I have no arms, we obtain a lower bound to the asymptotic threshold of 4.

No, I’m not going to have a title

I am Mel. Can we do some work now?

Progress update

The team at room 408 are currently trying to work out how to make this blog stop spamming us with emails.

scirate.com

Dabacon has started a new cite called scirate where anyone can register and then vote for papers that are listed on quant-ph. The general idea is to to ensure that good papers are seen by more people, which is great. However, the cite is essentially useless until more people register. So register, and then vote for us. Room 408 expects that after some time scirate will reach critical mass and then replace the arXiv as the place to go to when someone walks into the office and you have dinosaur comics in your browser. Or not.

yo, this is not the original title

Yo astephens, should the title be ’sticking’ or ’stinking’?