Questions tagged [pauli-gates]
For questions about Pauli matrices in general or Pauli gates in particular, as relevant to quantum computing and/or quantum information theory. The Pauli matrices are a set of three 2 × 2 complex matrices which are Hermitian and unitary. The three Pauli gates are: Pauli-X gate, Pauli-Y gate & Pauli-Z gate. X = {{0,1},{1,0}}; Y = {{0,-i},{i,0}}; Z = {{1,0},{0,-1}}.
269 questions
0 votes
1 answer
49 views
Asymptotic scaling of surface codes, why p and not 2p/3?
In Fowler's paper, "Surface codes: Towards practical large-scale quantum computation" (link), a rudimentary probabilistic model for logical errors is described. My only issue with this is ...
1 vote
2 answers
253 views
How to prove that identical Pauli commutation relations guarantee the existence of a conjugating unitary?
In this article: http://home.lu.lv/~sd20008/papers/essays/Clifford%20group%20[paper].pdf , the author calculates the order of the Clifford group and there is one step I'm not convinced. Consider $n$ ...
2 votes
1 answer
95 views
What is the circuit for $e^{-i \theta Z\otimes (X X + Y Y)}$?
I recently noticed that some quantum computers supply native gate $$iSWAP_{\theta} = e^{-i \theta (XX + YY)}.$$ I wonder, how do I build a circuit for $$e^{-i \theta Z\otimes(XX + YY)}$$ Is this one ...
2 votes
0 answers
107 views
Simplifiying trace of Paulis
Let $\mathcal{P}$ denote all Pauli operators (Heisenberg-Weyl operators in general). I want to see that $\frac{1}{d^4} \sum_{A_i, B_i \in \mathcal{P}} tr(A_1 U^\dagger B_1 U A_2 U^\dagger B_2 U \...
1 vote
1 answer
162 views
Non destructive implementation through phase estimation
Can you explain what is this circuit representing? it is supposed to perform measurement using Pauli operator P non destructively? How is that happening in this circuit?
0 votes
2 answers
105 views
Rotations that don’t change the outcomes probabilities in X and Z
Is there a rotation operator that doesn't change the outcome probability when measuring either on basis X or Z in the scenario where I only change the sign of the angle? I was thinking of $R_y(\pm\...
0 votes
1 answer
89 views
Mapping Pauli exponentiation into quantum circuits
This is a follow up of this question I am getting a bit confused about how to properly build a circuit implementing Pauli exponentiation. I usually start from the standard decomposition of $e^{-i \...
1 vote
2 answers
128 views
Exponentiating over sum of Paulis
According to this paper, for a given Hamiltonian $H$ we can build (efficiently) a circuit that implements $e^{-i \epsilon Y\otimes H}$. I know how to build the circuit in case $H$ is just a single ...
3 votes
2 answers
489 views
On Pauli matrices being a basis for unitary transformations
I am confused about the Pauli matrices. I am trying to decipher a statement like this: "[...]these three operators form a complete basis for the set of all unitary transformations on a single ...
6 votes
1 answer
369 views
Decompose a positive operator in Pauli basis
Define $\mathcal{P}_n$ to be the set of all $n$-qubit Pauli strings with phase $+1$. Then any Hermitian operator $H$ can be decomposed into linear combination of these Pauli strings. That is, $$ H=d^{-...
1 vote
1 answer
180 views
Understanding Qiskit's controlled-Pauli gates
I am learning how to use Qiskit's controlled Pauli gates. For example, I can create a simple three-qubit circuit containing controlled Pauli-XX and -ZZ gates using the code: ...
2 votes
2 answers
429 views
What are the square roots of the Hadamard gate?
Given the Hadamard gate $$H = \frac{1}{\sqrt{2}}\begin{pmatrix} 1 & 1 \\ 1 & -1\end{pmatrix}$$ what are the possible values of $\sqrt H$? And what is the geometrical interpretation of $\sqrt H$...
2 votes
2 answers
197 views
How to efficiently propagate the error from the decoder to the logical observable?
Suppose I run a Clifford circuit with noise and send the syndrome data to a decoder. Assume that the decoder's raw output tells me where in the circuit a particular Pauli error occurred. In this ...
3 votes
2 answers
339 views
How to find an operator that anticommutes with exactly one stabilizer and commutes with the rest?
Suppose I have a state stabilized by $S = \{S_1, S_2, ... S_n\}$. I want to find another state such that it is the $+1$ eigenstate of all $S_i$ where $i \neq 1$ and the $-1$ eigenstate of $S_1$. I ...
3 votes
1 answer
258 views
Prove that the entanglement definition of AME implies the error correction definition of AME
Consider a system of $ n $ qudits of size $ q $. Suppose that $ | \psi \rangle $ is an absolutely maximally entangled state. In other words, $ | \psi \rangle $ is a state such that the reduction to ...