6,069 reputation
1642
bio website jfitzsimons.org
location Singapore, Singapore
age 32
visits member for 3 years, 8 months
seen Dec 6 '13 at 16:11

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.


Jan
6
comment Information geometry of 1D Ising model in complex magnetic field regime
@WNY: I meant that if you plug such a Hamiltonian into the time dependent Schroedinger equation you get completely unphysical results. I understand from the above comments that you are simply using complex analysis on the conventional Hamiltonian, so I think my confusion has been cleared up. Sorry.
Jan
6
comment Information geometry of 1D Ising model in complex magnetic field regime
While I have a reasonable amount of experience with the Ising model, I'm not quite clear how exactly it makes sense to make $h$ complex. The dynamics of the system would then not only not be unitary, but would not even conserve total probability. Could you clarify?
Dec
29
comment Applications of Geometric Topology to Theoretical Physics
@AndrásBátkai: I'm not sure I agree that this should be CW. Let's wait to see if any one has a strong opinion either way.
Dec
29
comment Applications of Geometric Topology to Theoretical Physics
Have you heard about topological quantum computing? It is very closely linked to braid theory, which has given rise to a quantum algorithm for approximating the Jones polynomial.
Dec
20
comment Depolarizing threshold for CSS codes
@AshleyStephens: Great edit! Perhaps it should have been an answer it it's own right.
Dec
17
answered Depolarizing threshold for CSS codes
Dec
12
comment Higgs Field - Is its discovery truly “around the corner”?
@LarianLeQuella: I think perhaps you will not get answers before tomorrow. I imagine those in the know are embargoed from talking about it until tomorrow.
Dec
11
comment Spekkens Toy Model, Internal Comonoids
Welcome to the site, Ross!
Dec
9
comment Uniqueness of eigenvector representation in a complete set of compatible observables
That is incorrect. The Hamiltonian itself is an observable. Further, if you assign an arbitrary set of unique eigenvalues to the same eigenvectors (picking a basis for each degenerate subspace), thus lifting the degeneracy, this produces an observable which is simultaneously diagonalizable with the Hamiltonian, and hence commutes with it, but which has no degenerate eigenspaces.
Dec
7
comment Uniqueness of eigenvector representation in a complete set of compatible observables
@Moshe: I didn't bother looking at the Physics.SE link before answering, but now you've pointed it out I agree that genetth's answer was perfect.
Dec
6
comment Uniqueness of eigenvector representation in a complete set of compatible observables
Secondly, in quantum mechanics observable and Hermitian operator are synonymous. You can construct a physical measurement (in principle at least) for any Hermitian operator, and any physical observable is Hermitian.
Dec
6
comment Uniqueness of eigenvector representation in a complete set of compatible observables
$\psi_i$ above are a basis for the Hilbert space in which all measurements are diagonal. If the set of measurements is maximal then it necessarily contains $D$ for some specific choice of basis. Since you specify the set of observables by their eigenvectors, you can explicitly construct $D$.
Dec
6
answered Uniqueness of eigenvector representation in a complete set of compatible observables
Dec
2
comment Examples of number theory showing up in physics
That's weird, and certainly interesting. I'll give the paper a look.
Dec
2
comment Examples of number theory showing up in physics
Thanks for taking the time to compose an answer. I don't really consider quantum algorithms as fundamental physics in the sense of this question, particularly given that the hidden subgroup stuff is driven by a generalization of problems from number theory (factoring/discrete logs). The graph state observation seems more related to the fact that you are looking at factoring a Hilbert space, which directly relates to primality of the dimesnionality, etc.
Dec
2
comment Examples of number theory showing up in physics
@Artem: It's true that you can arrive at above result via finite fields, but the structure of the partial results is governed by number theoretic properties. I don't really see the way of arriving at a given result as particularly fundamental, as there are often multiple paths to the result.
Dec
2
comment What videos should everyone watch?
You may want to expand the question with a bit more explanation as in the cstheory question. I've marked this CW.
Dec
1
comment Examples of number theory showing up in physics
This seems more like engineering a physical system to embody certain number theoretic properties, rather than them occurring unexpectedly.
Dec
1
asked Examples of number theory showing up in physics
Nov
28
comment Quantum causal structure
@lurscher: Good catch. I'm not really sure where things stand then. I've updated my answer to include the reference in your comment.