Quantum Error Correction in the Surface Code (Part II): Logical State Preservation Experiments

Quantum error correction is an approach for preserving quantum information in the presence of decoherence and control errors. The surface code is unique in its high tolerance to errors. However, so far only error detection has been demonstrated in the surface code. Here, we report on progress towards realizing a distance-3 surface code, capable of correcting any single-qubit error on its 17 physical qubit constituents. We repeatedly measure all stabilizers of the code, extract bit- and phase-flip error syndromes, and characterize the overall performance in terms of the probability with which errors occur. Furthermore, we present a leakage detection scheme, allowing us to identify sequences in which any of the qubits was measured in a leakage state. Error correction is expected to be an essential ingredient in the realization of fault-tolerant universal quantum information processing.