Single-qubit quantum memory exceeding ten-minute coherence time

A long-time quantum memory capable of storing and measuring quantum information at the single-qubit level is an essential ingredient for practical quantum computation and communication(1,2). Currently, the coherence time of a single qubit is limited to less than 1 min, as demonstrated in trapped ion systems(3-)5, although much longer coherence times have been reported in ensembles of trapped ions(6,7) and nuclear spins of ionized donors(8,9). Here, we report the observation of a coherence time of over 10 min for a single qubit in a Yb-171(+) ion sympathetically cooled by a Ba-138(+) ion in the same Paul trap, which eliminates the problem of qubit-detection inefficiency from heating of the qubit ion(10,11). We also apply a few thousand dynamical decoupling pulses to suppress ambient noise from magnetic-field fluctuations and phase noise from the local oscillator(8,9,12-16). The long-time quantum memory of the single trapped ion qubit would be the essential component of scalable quantum computers(1,17,18), quantum networks(2,19,20) and quantum money(21,22).