Single-qubit quantum memory exceeding ten-minute coherence time

Abstract

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 171Yb+ ion sympathetically cooled by a 138Ba+ 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 . The longest coherence time of a single qubit of more than ten minutes is observed in a 171Yb+ ion. After sympathetically cooling the 171Yb+ ion qubit with a 138Ba+ ion, noise from magnetic-field fluctuations and the local oscillator is suppressed by a dynamic decoupling scheme.