Determining how to find the 2-d hilbert space from fusing ising anyons

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The discussion focuses on deriving and solving the pentagon equation to evaluate F matrices for Ising anyons in topological quantum computing. The author seeks to understand how to identify fusion paths that can generate a Hilbert space, particularly in relation to equation 1.6, which determines the dimension of anyon sets based on fusion rules. They express confusion about applying this equation to demonstrate that three σ anyons yield a dimension of 2. The importance of identifying valid fusion paths is emphasized due to the complexity introduced by the pentagon identity involving multiple anyons. Additionally, the author questions how braiding affects fusion outcomes, seeking clarity on the relationship between braiding phases and fusion results.
Shinn497
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Hello all,

I'm working through the following paper on topological quantum computing.

http://www.qip2010.ethz.ch/tutorialprogram/JiannisPachosLecture

In particular I'm trying to derive and solve the pentagon equation in order to evaluate the F matrices for ising anyons. One thing I'm trying to determine is how to determine, in general, which fusion paths can become a 2-d hilbert space. I understand that the fusion paths in figure 1.4a are analogues of the |0> |1>, and |+> |-> hilbert spaces but I don't get if there is a way to find any others...in general.

I think what would really help is equation 1.6, which determines the dimensional of of a set of anyons based on the fusion rules. BUT I'm not entirely sure how to read that equation. In particular I can't get how it is used to properly get the dimension of 3 σ anyons to be 2. I was able to prove it by drawing it out and doing the fusions but I couldn't use that one equation.

This is important because the pentagon identity is for 4 anyons. This means there are a 243 possible fusion paths. In the intermediate steps of the equation there are more. If there was a better way of determining which fusion paths are within the fusion rules that would be great.

Thanks for your help!

EDIT: I meant to say hilbert spaces in general they do not have to be 2-DSecondary question:

Why does braiding effect the fusion? This is the central idea to what makes quantum computation with anyons possible but I'm not getting it. I'll accept that anyons gain a phase when braided but I'm not sure how this phase effects the fusion outcome in general. In other words, can you explain figure 1.3?
 
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I believe I found my answer.
 
Time reversal invariant Hamiltonians must satisfy ##[H,\Theta]=0## where ##\Theta## is time reversal operator. However, in some texts (for example see Many-body Quantum Theory in Condensed Matter Physics an introduction, HENRIK BRUUS and KARSTEN FLENSBERG, Corrected version: 14 January 2016, section 7.1.4) the time reversal invariant condition is introduced as ##H=H^*##. How these two conditions are identical?

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