Norbert Schuch's user avatar
Norbert Schuch's user avatar
Norbert Schuch's user avatar
Norbert Schuch
  • Member for 6 years, 1 month
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17 votes

Can quantum states have negative probability?

12 votes
Accepted

Are there quantum algorithms showing a double exponential advantage?

11 votes
Accepted

What does it mean "less than identity" in the operator sum representation?

11 votes
Accepted

Do the Kraus operators of a CPTP channel need to be orthogonal?

10 votes
Accepted

How to construct a multi-qubit controlled-Z from elementary gates?

9 votes

Maximally mixed states for more than 1 qubit

9 votes

Quantum Supremacy: How do we know that a better classical algorithm doesn't exist?

8 votes
Accepted

How to find the operator sum representation of the depolarizing channel?

8 votes
Accepted

What does it mean to take the Choi-Jamiolkowski of a quantum channel?

7 votes
Accepted

Can any channel be written as $\Phi(X)=\operatorname{Tr}_{\mathcal Z}[U(X\otimes \sigma)U^\dagger]$ for any state $\sigma$?

7 votes

What is an example of a separable measurement that is not LOCC?

7 votes

What is the expectation value ${\Bbb E}[\langle\psi,O\psi\rangle]$ over the Haar distribution?

7 votes
Accepted

CS conjecture that Quantum Computer cannot solve NP-complete problems, but Boson Samplers do a #P-hard problem. How is it?

7 votes
Accepted

How is a promise gap related to a spectral gap?

6 votes

If a Hamiltonian is quadratic in the ladder operator, why is its time evolution linear in the ladder operator?

6 votes
Accepted

Why is $\Phi\otimes \operatorname{Id}_n$ being positive on maximally entangled states sufficient to know that $\Phi$ is CP?

6 votes
Accepted

Why do stabilizer cut the Hilbert space into two halves?

6 votes
Accepted

Are there techniques to reduce the number of Pauli strings in a Hamiltonian?

6 votes
Accepted

What can we say about the eigendecomposition of quantum channels?

6 votes
Accepted

Trace distance of two classical-quantum states

6 votes

Controlling high-dimensional Hilbert spaces with a single qubit

6 votes

What do we mean by the notation $\lvert \mathbf{x}, 0\rangle$?

6 votes

What is the matrix of the iSwap gate?

6 votes
Accepted

Shorthand notation for the sign flip gate

6 votes

How to construct Deutsch's gate or $\pi/8$ rotations using Toffoli+Hadamard?

6 votes

If an auxiliary qubit is allowed, how to construct toffoli gate in easier way?

6 votes

Why do purifications only differ by a local unitary?

5 votes

How would I implement the quantum oracle in Deutsch's algorithm?

5 votes

Are superpositions of an infinite number of states realizable?

5 votes
Accepted

Do we know anything about the computational complexity of the exchange-correlation functional?

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