J Chiaverini, Dietrich G. Leibfried, Tobias Schaetz, Murray D. Barrett, Brad R. Blakestad, Joseph W. Britton, Wayne M. Itano, John D. Jost, Emanuel H. Knill, C. Langer, R Ozeri, David J. Wineland
Scalable quantum computation and communication require error control to protect quantum information against unavoidable noise. Quantum error correction protects quantum information stored in two-level quantum systems (qubits) by rectifying errors with unitary operations conditioned on projective measurement outcomes. Here we experimentally demonstrate quantum error correction using three beryllium atomic-ion qubits confined to a linear , multi-zone trap. One logical state is protected against spin-flip errors by means of a repeatable three-qubit quantum error-correcting code that has no classical analog. In the experiment, a primary ion qubit is prepared in an initial state, which is then encoded into the primary and two ancilla qubits. Errors are induced at various rates. The logical state is decoded to the primary ion qubit, making error information available on the ancilla ions, which are separated from the primary ion and measured. The final step is to correct the primary qubit state based on the measurement outcomes. We verify error correction by comparing the corrected final state to the uncorrected state and to the initial state. Such implementations of quantum error correction are an important step towards scalable fault-tolerant quantum computation using trapped ions.