# Quantum error correction: block length and error rate definitions

I encountered notions of block length and error rate for quantum error correcting codes, which literature seems to just assume. Can someone please give precise definitions for these?

Usually we denote a quantum code by parameters $$[[n,k,d]]$$. Where $$n$$ is the number of physcial qubits used, $$k$$ - number of encoded (or logical) qubits, and $$d$$ the code distance.

Besides the definitions, how are block length and error rate related to those parameters $$n,k$$ and $$d$$?

The block length is defined as the number of physical qubits you are using to encode the logical qubit. Thus in the parameters $$[n,k,d]$$ the value $$n$$ is your block length.