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In Gottesman's introduction, it writes
A code that corrects t errors is said to have distance 2t + 1, because it takes 2t + 1 single-qubit changes to get from one codeword to another.
Other reviews have slight different definitions but I think they are all equivalent. I am still new to QEC...and a little confused about how these $2t+1$ single-qubit changes take place during quantum error correction..Could anyone give a more detailed explanation?