Joe Fitzsimons

5,596 reputation

1237

bio	website	jfitzsimons.org
	location	Singapore, Singapore
	age	31
visits	member for	2 years, 6 months
	seen	May 18 at 22:33
stats	profile views	453

I have just moved to the Center for Quantum Technologies in Singapore, after spending the last 3 years as a Merton College JRF in Theoretical Physics and a Senior Research Fellow in Oxford University Department of Materials. My research focuses largely on theoretical aspects of quantum information processing. In particular I am interested in spin networks, measurement based computation, cryptography and computational complexity.

	5,596 reputation	bio	website	jfitzsimons.org	visits	member for	2 years, 6 months
1237 badges		location	Singapore, Singapore		seen	May 18 at 22:33

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Oct 18	comment	What methods are there to deal with quantum spatiotemporal chaos? I'm not quite sure what you mean by "the qualitative distribution" of a one dimensional cellular automata. Could you clarify this? Two alternating species are sufficient for Turing completeness, given an appropriate update rule.
Oct 18	comment	Graduate School for Theoretical Physics I have to agree with Moshe's last comment. However, I did upvote the question, because I think it is one of the more important types of soft-question.
Oct 18	comment	Graduate School for Theoretical Physics The reason I'm asking is that I think you are perhaps being disingenuous in your view of theoretical physicists. Many papers are themselves mathematically rigorous, but are build on less rigorous foundations (i.e. renormalization etc.). I'm not clear how you view such work. You say your interests lie in QFT, so this is quite important, since unless you are interested only in AQFT, you'll likely find yourself using well established but less rigorous approaches.
Oct 18	comment	Graduate School for Theoretical Physics Could you give us a couple of examples of TP papers you feel are representative of the physics level of rigor? At present, I'm not really clear on where you draw the line.
Oct 16	comment	direct sum of anyons? @NoahSnyder: That is incorrect. For Fibonacci anyons $\phi\otimes\phi\otimes\phi = \mathbb{I} \oplus \phi \oplus \phi$ which is exactly 3 levels. Each $\phi$ in the direct product corresponds to a single dimension. (see for example p17 of rockpile.phys.virginia.edu/trieste08.pdf ).
Oct 16	comment	direct sum of anyons? @André: That's not what the notation means. $\phi + \phi$ is not adding two vectors, but rather creating a 2D vector space from 2 1D vector spaces.
Oct 16	comment	Connections of iterative solvers for large systems of equation in Physics? What type of equations?
Oct 16	comment	direct sum of anyons? +1: A far clearer answer than mine.
Oct 16	comment	direct sum of anyons? @André: Check out Chapter 2 of the first link. They are specifically using qubits encoded in $\mathbb{I} + \mathbb{I}$. Specifically these correspond to the two different ways to fuse four anyons to obtain the vacuum. There are several ways this can be achieved. (see for example quant-ph/0703143 where anyons are encoded as topological defects in a lattice of qubits)
Oct 16	comment	Does the complex 3-sphere have a complex structure modulus? Can you point us towards the section in the paper where that claim is made (it's a long paper)?
Oct 16	comment	direct sum of anyons? @Heidar: Sorry, hadn't seen your answer when I posted this. I guess we were writing them at the same time.
Oct 13	comment	Models of higher Chern-Simons type It is certainly fine to answer your own question if you later find the answer. It's certainly preferable to having unanswered questions.
Oct 12	comment	Random Walk Randomly Reflected @RonMaimon: I have an answer for the asymmetric case too (somewhat different to yours), but it might make more sense to wait for the other question, since it is a completely different argument.
Oct 12	comment	Random Walk Randomly Reflected @Leandro: No problem. As far as I can see this question actually amounts to a random walk on a weighted graph with a certain structure. The most obvious generalization would be a walk on a weighted directed graph, which would give you the direction dependent reflectors.
Oct 11	comment	Random Walk Randomly Reflected @Leandro: No problem.
Oct 10	comment	What do theoretical physicists need from computer scientists? Prakash is something of a special case, as he has a significant background in physics.
Oct 6	comment	What is the use of a Universal-NOT gate? I think universal decoupling pulses may be possible, but we know for a fact that the universal-NOT isn't.
Oct 6	comment	Random Walk Randomly Reflected How are you measuring distance from the oracle? Is it the Euclidean norm?
Oct 6	comment	Does entropy measure extractable work? Actually I guess the issue is clouded by the existence of alternative non-equivalent definitions of entropy.
Oct 6	comment	What is the use of a Universal-NOT gate? Yes, dynamical decoupling is one reason you may want a universal-NOT. However, given that these don't exist, you are likely far better with WaHuHa pulses and refinements there of, than using approximate universal-NOTs. After all, you only need the effective change to add up to zero, and having more than two types of evolution involved doesn't change that end result (see my comment on Marco's answer above). +1 anyway though, as it is indeed a reason for wanting a universal-NOT.