Long-Lived Qubit Memory Using Atomic Ions
C. Langer, Roee Ozeri, John D. Jost, John Chiaverini, Brian DeMarco, Amit Ben-Kish, R. B. Blakestad, J. Britton, David B. Hume, Wayne M. Itano, Dietrich G. Leibfried, R. Reichle, Till Rosenband, Tobias Schaetz, Piet O. Schmidt, D. J. Wineland · Physical Review Letters · 2005
We demonstrate experimentally a robust quantum memory using a magnetic-field-independent hyperfine transition in 9Be+ atomic ion qubits at a magnetic field B approximately = 0.01194 T. We observe that the single physical qubit memory coherence time is greater than 10 s, an improvement of approximately 5 orders of magnitude from previous experiments with 9Be+. We also observe long coherence times of decoherence-free subspace logical qubits comprising two entangled physical qubits and discuss the merits of each type of qubit.