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3 votes
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Does Gottesman-Knill theorem apply with any computational basis input?

The two constraints on preparations are equivalent in the presence of Clifford gates. More precisely, for any $x=x_1x_2\dots x_n\in\{0,1\}^n$, we can prepare $|x\rangle$ in $O(1)$ time using $$|x\...
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5 votes
Accepted

If sampling the output of $U_1U_2$ is easy, is sampling the output of $(U_1U_2)^\dagger$ also easy?

We know that $$\begin{eqnarray} P_{(U_1U_2)^{\dagger}}(y\ \vert\ x) &=& \left\vert\langle y\vert(U_1U_2)^{\dagger}\vert x\rangle\right\vert^2 = \left\vert\left(\langle x\vert U_1U_2\vert y\...
  • 138
1 vote

If sampling the output of $U_1U_2$ is easy, is sampling the output of $(U_1U_2)^\dagger$ also easy?

Intuitively, I would say that if $P_{U_1U_2}(y|x)$ is efficiently sampleable, also $P_{(U_1U_2)^\dagger}(y|x)$ is efficiently sampleable as the quantum circuit for $(U_1U_2)^\dagger$ is just the ...
3 votes
Accepted

Status of Google's quantum supremacy claim 2022

The paper simulating the random circuit sampling task was published in PRL. An even larger scale simulation verified the 53 qubit, 20 cycle Google results directly. RE repeating the experiments, ...
  • 502
2 votes

How to convert a quantum circuit into a tensor network?

Quantum circuits are effectively already a special type of tensor networks. We just need to interpret them appropriately to see this. Normally, we think of lines as representing qubits and boxes as ...
  • 18.2k
0 votes

Exact expectation value of a quantum circuit simulated with the matrix product state method in qiskit

By default, the matrix product state method in Qiskit does not compute the state vector when computing the expectation value for a Pauli matrix. For a general matrix, it does compute the density ...

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