Active readout-error mitigation

Mitigating errors is a significant challenge for near term quantum computers. One of the most important sources related to readout state into classical bit stream. A variety techniques have been proposed mitigate these with post-hoc corrections. We propose complementary scheme actively reduce on shot-by-shot basis by encoding single qubits, immediately prior readout, multi-qubit states. The computational resources our technique are independent circuit depth and fully compatible current hardware error rates connectivity. analyze potential approach using two types error-correcting codes and, as proof principle, demonstrate an 80% improvement in IBMQ Mumbai computer.