Single ion qubit with estimated coherence time exceeding one hour

Abstract

Realizing a long coherence time quantum memory is a major challenge of current quantum technology. Until now, the longest coherence-time of a single qubit was reported as 660 s in a single 171Yb+ ion-qubit through the technical developments of sympathetic cooling and dynamical decoupling pulses, which addressed heating-induced detection inefficiency and magnetic field fluctuations. However, it was not clear what prohibited further enhancement. Here, we identify and suppress the limiting factors, which are the remaining magnetic-field fluctuations, frequency instability and leakage of the microwave reference-oscillator. Then, we observe the coherence time of around 5500 s for the 171Yb+ ion-qubit, which is the time constant of the exponential decay fit from the measurements up to 960 s. We also systematically study the decoherence process of the quantum memory by using quantum process tomography and analyze the results by applying recently developed resource theories of quantum memory and coherence. Our experimental demonstration will accelerate practical applications of quantum memories for various quantum information processing, especially in the noisy-intermediate-scale quantum regime.

Simulating a measurement-induced phase transition for trapped-ion circuits

“…We consider N trapped atomic ions, each with two internal energy levels behaving as an effective qubit system. In current experimental hardware, these two qubit states have been shown to be long-lived and highly coherent [37], with accurate initialization through optical pumping and qubit readout via fluorescence imaging. The qubits are manipulated coherently [30] using external laser fields, capable of applying phasesensitive single-and two-qubit quantum gates mediated by collective vibrational (phonon) modes.…”

Efficient Quantum Network Communication using Optimized Entanglement-Swapping Trees

“…Fidelity is modeled in NetSquid using two parameter values, viz., depolarization (for decoherence) and dephasing (for operations-driven) rates. We conservatively choose a depolarization rate of 0.01 such that the fidelity after 1 min is 90%, based on demonstrated coherence times of several minutes [29,34] to hours [37,40]. Similarly, we choose a dephasing rate of 1000 which corresponds to a link EP fidelity of 99.5% [9].…”

“…Link generation latencies for 5 to 100km links range from about 3 to 350 milliseconds for typical network parameters[8], while coherence times of few seconds is very realistic (coherence times of several seconds[18,24] have been shown long ago, and more recently, even coherence times of several minutes[29,34] to a few hours[37,40] have been demonstrated.…”

Sympathetic cooling of a large ${}^{113}\mathrm{Cd}^{+}$ ion crystal with ${}^{40}\mathrm{Ca}^{+}$ in a linear Paul trap

“…For example, the 27 Al + optical atomic clock sympathetically cooled by 25 Mg + has reached an extremely high-stability below 10 −18 [18]. The qubit of 171 Yb + sympathetically cooled by 138 Ba + has the longest coherence-time up to around 5500 s [19]. As for large-number (> 1000) ion systems, they are often applied in the fields of precision measurement and spectroscopy because of their high signal-to-noise ratio.…”