QUROPE Quantum Information Processing and Communication in Europe

We present optimal control protocols to prepare different many-body quantum states of Rydberg atoms in optical lattices. Specifically, we show how to prepare highly ordered many-body ground states, GHZ states as well as some superposition of symmetric excitation number Fock states, that inherit the translational symmetry from the Hamiltonian, within sufficiently short excitation times minimizing detrimental decoherence effects.

We use the sensitive response to electric fields of Rydberg atoms to characterize all three vector components of the local electric field close to an atom-chip surface. We measured Stark-Zeeman maps of S and D Rydberg states using an elongated cloud of ultracold Rubidium atoms (T ~2.5 µK) trapped magnetically 100 µm from the chip surface. The spectroscopy of S states yields a calibration for the generated local electric field at the position of the atoms.

In conventional nonlinear optics, linear quantum optics

Quantum-state engineering is of critical importance to the development of quantum technologies. One promising platform is thermal atomic vapours, because they offer long coherence times with reproducible and scalable hardware. However, the inability to address isolated atomic states in a controlled manner, due to multi-level degeneracy and motional broadening, is a major obstacle to their wider application.

We present an object-oriented Python library for computation of properties of highly-excited Rydberg states of alkali atoms.

We investigate the nonequilibrium dynamics of a driven-dissipative spin ensemble with competing power-law interactions. We demonstrate that dynamical phase transitions as well as bistabilities can emerge for asymptotic van der Waals interactions, but critically rely on the presence of a slower decaying potential core.

We demonstrate a method for probing interaction effects in a thermal beam of strontium atoms using simultaneous measurements of Rydberg EIT and spontaneously created ions or electrons. We present a Doppler-averaged optical Bloch equation model that reproduces the optical signals and allows us to connect the optical coherences and the populations.

We address the technical challenges when performing quantum information experiments with ultracold Rydberg atoms in lattice geometries. We discuss the following key aspects: (i) the coherent manipulation of atomic ground states, (ii) the coherent excitation of Rydberg states, and (iii) spatial addressing of individual lattice sites.