Experimental Demonstration of Quantum Error Detection with a Small Surface Code

One of the most promising approaches for quantum error correction is the surface code, which consists of a d×d grid of data qubits combined with a set of ancilla qubits. The surface code implements a distance-d quantum error correction code that allows for the detection of d-1 errors per stabilizer-measurement cycle. The smallest non-trivial surface code that allows for complete quantum error detection of a logical qubit subspace is the d=2 surface code, consisting of 4 data qubits and 3 ancilla qubits for the stabilizer measurements.Here we present experimental results obtained on a small seven-qubit surface code device implemented in superconducting circuits. We present measurements of all three stabilizers with high fidelity and repeated detection of errors on the data qubits using the stabilizer readout.