Coherence Preserving Ion-loss Error-detection Protocol

In a system of trapped ions, ion loss is inevitable due to collisions or chemistry with background gasses. To minimize the impact of these loss errors on a quantum algorithm, it would be beneficial to detect them without decohering the quantum state of any computational ions. For this purpose, we have developed an error-detection protocol which merges and separates an ancilla and a computational ion. Subsequent detection of fluorescence from the ancilla indicates that both ions remain in the trap, while absence of fluorescence indicates that at least one of the ions has been lost. We experimentally demonstrate that the protocol does not significantly heat or decohere the computational ion. This protocol could be useful for post-processing of data or could be integrated actively into error correction.