# Regensburg 2022 – wissenschaftliches Programm

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# QI: Fachverband Quanteninformation

## QI 4: Poster: Quantum Information

### QI 4.40: Poster

### Montag, 5. September 2022, 18:00–20:00, P2

Improving the Sørensen-Mølmer gate using analytical optimal control — •Susanna Kirchhoff^{1,2}, Frank K. Wilhelm^{1,2}, and Felix Motzoi^{3} — ^{1}Forschungszentrum Jülich, Quantum Computing Analytics (PGI 12), D-52425 Jülich, Germany — ^{2}Theoretical Physics, Saarland University, 66123 Saarbrücken, Germany — ^{3}Forschungszentrum Jülich, Institute of Quantum Control (PGI-8), D-52425 Jülich, Germany

The Sørensen-Mølmer gate is an entangling gate for ion qubits [1]. The entangled state is obtained by the application of a bichromatic light beam which collectively drives the ions. This leads to an entangling gate if certain conditions on gate time, drive frequency and amplitude are fulfilled. These conditions can be derived from the propagator. However, the gate is not perfect. In [1] the authors apply the Lamb-Dicke approximation and neglect some fast rotating terms as well as the single qubit rotation before calculating the propagator. This leads to gate errors. We investigate how the approximations affect the gate fidelity and explore methods to avoid those errors and make the gate more robust against heating.

[1] Sørensen and Mølmer: Entanglement and quantum computation with ions in thermal motion. In: Physical Review A 62.2 (2000)