# Mainz 2017 – wissenschaftliches Programm

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# Q: Fachverband Quantenoptik und Photonik

## Q 47: Quantum Computing I

### Q 47.1: Gruppenbericht

### Donnerstag, 9. März 2017, 14:30–15:00, P 2

**Generation and application of scalable entanglement in an ion trap** — •Thomas Ruster, Henning Kaufmann, Jonas Schulz, David von Lindenfels, Vidyut Kaushal, Christian T. Schmiegelow, Ferdinand Schmidt-Kaler, and Ulrich Poschinger — Institut für Physik, Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany

Entanglement is an important resource for applications such as quantum computation and high precision sensing. In a segmented Paul trap, entanglement can be created by combining laser-driven logic gates and ion-shuttling operations. We present how we encode a qubit with coherence times in the 1 s range in the valence electron spin of ^{40}Ca^{+} ions. The implementation of the set of shuttling operations required for scalable protocols is outlined. We show how to conduct high-fidelity gate operations, which are insensitive against motion excited by the shuttling operations.

We combine gate and shuttling operations to generate a 4-ion GHZ state | ↑ ↑ ↑ ↑ > + | ↓ ↓ ↓ ↓ >. By applying dynamical decoupling techniques, we can keep the entangled state alive for about 1 s.

As an application of spatially distributed entanglement, we employ Bell states | ↑ ↓ > + | ↓ ↑ > for sensing inhomogeneous magnetic fields. These states accumulate a phase, which depends on the magnetic field difference between the locations of the constituent ions. By measuring the accumulated phase, we map out dc magnetic fields with accuracies down to 270 pT.