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A: Fachverband Atomphysik

A 2: Ultracold Atoms, Ions and Molecules I (with Q)

A 2.3: Vortrag

Montag, 29. Februar 2016, 11:30–11:45, e001

Investigation of hyperfine qubit dephasing in trapped ions — •Theeraphot Sriarunothai, Christian Piltz, Gouri Giri, and Christof Wunderlich — Department Physik, Universität Siegen, 57068 Siegen, Germany

Magnetic sensitive hyperfine states of trapped ions that serve as qubits can be protected against decoherence by use of continuous or pulsed dynamical decoupling (e.g., [1]). Nevertheless it is desirable to experimentally identify noise sources and characterize them to enhance the basic stability of experiments in quantum information science. We report on investigations into the dephasing of hyperfine qubits exposed to a magnetic gradient using trapped ¹⁷¹Yb⁺ ions confined in a macroscopic linear Paul trap. Effective magnetic field noise caused by the ions’ motion in varying electric fields is reduced by minimizing the ions’ micromotion and by passively filtering the DC potentials applied to trap electrodes. An active magnetic field compensation system counteracts ambient magnetic noise. The dependence of the fidelity of conditional quantum gates (e.g., CNOT) is investigated as a function of the thermal excitation of the ions’ motion in the range between the Doppler cooling limit and close to the motional ground state employing microwave sideband cooling [2-4].

[1] N. Timoney et al., Nature 476, 185 (2011).

[2] C. Ospelkaus et al., Nature 476, 181 (2011).

[3] A. Khromova et al., Phys. Rev. Lett. 108, 220502 (2012).

[4] S. Weidt et al., Phys. Rev. Lett. 115, 013002 (2015.)