In quantum information, the gnu code refers to a particular family of quantum error correcting codes, with the special property of being invariant under permutations of the qubits.
Given integers g (the gap), n (the occupancy), and m (the length of the code), the two codewords are where
are the Dicke states consisting of a uniform superposition of all weight-k words on m qubits, e.g.
The real parameter
scales the density of the code.
, the gnu code is capable of correcting