# Tag Info

## New answers tagged quantum-channel

1

I think your misunderstanding is in the wording of the secret key rate; The PLOB-Bound offers an asymptotic, ultimate-upper bound on the secret key rate per use of a lossy bosonic channel. This bound on the secret key rate is computed as a regularisation, where one considers the infinite limit of $n \rightarrow \infty$ transmissions across the channel in ...

1

A probability distribution over unitaries {(p_1, U_1),..., (p_k, U_K)}, where you select U_i with probability p_i, is equivalent to Kraus operators \sqrt{p_1}U_1,..., \sqrt{p_k}U_k. For example, the bit flip error can be implemented by randomly deciding whether to leave the state unchanged (with probability p) or apply an X gate (with probability 1-p). With ...

1

Qiskit simulator behaves like this for your code snippet: whenever it encounters one of u1, u2, or u3 gates (in the compiled circuit), it first applies the gate; then it performs an X gate according to the provided probability (0.05 in our case).

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