Efficient Decoherence Control Algorithms

6 Subsystem Codes

Subsystem codes were recently introduced in an effort to unify quantum error-correcting codes, decoherence free subspaces, and noiseless subsystems. A subsystem code C = A ⊗ B  is a subspace of a finite-dimensional Hilbert space that is decomposed into a tensor product of two vector spaces A  and B  , respectively called the subsystem A  and the co-subsystem B  . The main idea is that the information is encoded in the subsystem A  and that all errors affecting the co-subsystem B  are ignored.

Clifford codes are the most natural way to construct subsystem codes such that C  is a stabilizer code, the dimensions of A  and B  can be controlled, and the set of detectable errors can be determined.

One of our key results is that any additive classical error-correcting codes yields a subsystem code, no self-orthogonality is needed!