User Frederik vom Ende

21 votes

6 answers

1k views

Counterexamples in quantum information theory

asked Apr 15 at 12:33

2 votes

1 answer

499 views

Diamond norm distances between some channel and the identity

asked Jun 23, 2023 at 16:05

5 votes

1 answer

260 views

For how many different times do I have to know that $e^{tL}$ is a quantum channel to conclude that $L$ is of Lindblad form?

asked May 7 at 16:01

5 votes

1 answer

228 views

Is the trace of a positive map always positive?

asked Apr 30 at 11:50

4 votes

1 answer

182 views

Is the closest diagonal state to a given state always the dephased original state?

asked yesterday

1 vote

1 answer

82 views

Can the spectral radius of a completely positive map exceed the spectral radius of its transition matrix?

asked May 14 at 15:10

1 vote

1 answer

76 views

To what extent is the normal form of the Pauli transfer matrix unique?

asked May 2 at 12:01

2 votes

1 answer

62 views

Is the adjoint of a strictly positive channel again strictly positive?

asked May 20 at 17:20

2 votes

1 answer

55 views

Is the extension of a pure operation also a pure operation?

asked Aug 2 at 9:19

2 votes

1 answer

50 views

If states are close together does there always exist a channel close to the identity mapping one to the other?

asked Apr 29 at 15:05

1 vote

1 answer

41 views

Is every quantum channel covariant with respect to some non-trivial Hamiltonian?

asked May 7 at 12:44

1 vote

1 answer

39 views

Are Stinespring unitaries that give rise to the same channel locally unitarily equivalent?

asked May 28 at 13:34

1 vote

1 answer

32 views

Are peripheral eigenvalues of a completely positive map always semisimple?

asked Jun 12 at 14:27

0 votes

1 answer

32 views

Given $\Psi$ completely positive when do there exist $K_1,K_2$ such that $K_2\Psi(K_1^\dagger(\cdot)K_1)K_2^\dagger$ is also trace preserving?

asked May 27 at 16:14

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14 Questions

Counterexamples in quantum information theory

Diamond norm distances between some channel and the identity

For how many different times do I have to know that $e^{tL}$ is a quantum channel to conclude that $L$ is of Lindblad form?

Is the trace of a positive map always positive?

Is the closest diagonal state to a given state always the dephased original state?

Can the spectral radius of a completely positive map exceed the spectral radius of its transition matrix?

To what extent is the normal form of the Pauli transfer matrix unique?

Is the adjoint of a strictly positive channel again strictly positive?

Is the extension of a pure operation also a pure operation?

If states are close together does there always exist a channel close to the identity mapping one to the other?

Is every quantum channel covariant with respect to some non-trivial Hamiltonian?

Are Stinespring unitaries that give rise to the same channel locally unitarily equivalent?

Are peripheral eigenvalues of a completely positive map always semisimple?

Given $\Psi$ completely positive when do there exist $K_1,K_2$ such that $K_2\Psi(K_1^\dagger(\cdot)K_1)K_2^\dagger$ is also trace preserving?