  A five-qubit codeword stabilized quantum code is implemented in a seven-qubit
system using nuclear magnetic resonance (NMR). Our experiment implements a good
nonadditive quantum code which encodes a larger Hilbert space than any
stabilizer code with the same length and capable of correcting the same kind of
errors. The experimentally measured quantum coherence is shown to be robust
against artificially introduced errors, benchmarking the success in
implementing the quantum error correction code. Given the typical decoherence
time of the system, our experiment illustrates the ability of coherent control
to implement complex quantum circuits for demonstrating interesting results in
spin qubits for quantum computing.
