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Topological order is a new kind of order in quantum matter, which corresponds to pattern of long-range quantum entanglement. See http://en.wikipedia.org/wiki/Topological_order

2 votes
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Interpretation of Majorana's wave function

For the first part, although it does not quite make sense to ask "the probability to have a Majorana in position x" (there are no "Majorana" in the system; the system only has electrons), the wavefunc …
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4 votes
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The Quantum Double of a Group and its relation to discrete gauge theories

Strictly speaking, the statement in your question is not quite accurate: the excitations in the quantum double are classified by irreducible representations of D(G), which is a Hopf algebra. Then one …
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2 votes
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$Z_2$ invariants in quantum spin hall (QSH)

It is not true that if $\mathbf{k}\neq -\mathbf{k}$ the matrix element $\langle u_i(\mathbf{k}|T|u_j(\mathbf{k})\rangle$ vanishes. Remember that $u(\mathbf{k})$ are Bloch wavefunctions, which are eige …
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2 votes
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1D Hermitian Hamiltonians are topologically trivial?

The statement cited is misleading. If the system is bosonic, and no symmetry is considered, then indeed all gapped Hermitian Hamiltonians are trivial. With symmetry there can be distinct symmetry-prot …
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6 votes

What does a zero topological S matrix element mean?

Let us consider the S matrix of Ising anyons as an example: $S_{\sigma\sigma}=0$. To be more precise, suppose we have four $\sigma$'s, labeled as $1,2,3,4$. We assume $1$ and $2$ are in a definite fu …
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4 votes
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Questions on gapless edge excitations in symmetry-protected topological state

Q1: Consider the example of a Haldane phase protected by time-reversal symmetry. There is a spin-1/2 on the edge, and to polarize it (so the system is gapped and the ground state is unique) one must b …
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3 votes

Interacting fermionic SPT phases in 2d with time-reversal symmetry

The non-interacting classification was obtained in the seminal "periodic table" papers by Kitaev and Ryu/Snyder/Furusaki/Ludwig. The interacting classification of 2D fermionic SPT phases with time-rev …
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2 votes
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Why is the plaquette operator in the string-net model a projection operator?

The relevant part of the sum as $\sum_{k^*,s_1,s_2}\delta_{k^*,s_1s_2}d_{s_1}d_{s_2}B^k_P$ Let me assume that the fusion category has no multiplicities, so $N_{ab}^c=0,1$, which I think Levin and We …
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2 votes
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Berry phase in the toric code model and 2D chiral $p$-wave superconductors

For 2D chiral p-wave, it has been shown that the Berry phase contribution vanishes and therefore the exchange statistics is entirely given by the monodromy. This was done in http://arxiv.org/abs/cond- …
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2 votes
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How can a torus admit half a flux quantum, and why does a vortex induce an AB phase?

I'll try to answer the last question, which is of course closely related to the first one (in bold font). The existence of half flux quanta is special to Moore-Read state (the paper cited in the OP c …
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1 vote

Why are there $F$-symbols in the splitting in anyon theory?

The splitting is not just $F$ symbols. There are also non-universal tunneling amplitudes $\Gamma_e$, which will compensate for the gauge transformations of $F$. In the end of the day, what we may lear …
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5 votes
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Topological Quantum Computing beyond Anyonic Braiding

The first question is in a system supporting anyons, what are the universal/topologically invariant physical quantities? Our current theoretical understanding is that all such quantities are related i …
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3 votes

Which topological orders described by TQFT and tensor category theories are not known to be ...

I'll offer an alternative route to engineer a Hamiltonian to realize a general 2+1 TQFT. Again working out details is very challenging and have only been done for some special cases. The idea is to us …
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2 votes

Topological phase and Chern number

When the Chern numbers of the two bands go from $(1,-1)$ to $(-1,1)$, the Chern number of the occupied band changes sign. Even though the number of chiral edge modes is the same, they have opposite ch …
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6 votes
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How many of Kitaev's "Odds and Ends" in his 2006 anyon paper have been solved?

1 has been partially solved in the following sense: Iridates amazingly have Kitaev interaction (among other interactions). 2 a lot has been known about this kind of phenomena, now part of the story of …
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