  We present a simple and fast numerical procedure to search for good quantum
codes for storing logical qubits in the presence of independent per-qubit
noise. In a key departure from past work, we use the worst-case fidelity as the
figure of merit for quantifying code performance, a much better indicator of
code quality than, say, entanglement fidelity. Yet, our algorithm does not
suffer from inefficiencies usually associated with the use of worst-case
fidelity. Specifically, using a near-optimal recovery map, we are able to
reduce the triple numerical optimization needed for the search to a single
optimization over the encoding map. We can further reduce the search space
using the Cartan decomposition, focusing our search over the nonlocal degrees
of freedom resilient against independent per-qubit noise, while not suffering
much in code performance.
