Implementation in Qiskit of a quantum error correction code via entanglement distillation on a QKD BBM92 protocol as seen on https://arxiv.org/abs/1810.03267 (Apendix A)
It is desinged to detect a single bit flip with the hash matrix in which each column corresponds to the qubit number in binary.
Eg. for a 7 qubit key the hashing matrix is:
$ H = \begin{pmatrix} 0 & 0 & 0 & 1 & 1 & 1 & 1 \ 0 & 1 & 1 & 0 & 0 & 1 & 1 \ 1 & 0 & 1 & 0 & 1 & 0 & 1 \end{pmatrix} $