We present a series of four experiments unveiling intriguing characteristics of structured beams when interacting with individual, well-localized atoms. The initial investigation explores the placement of a single atom within the dark center of a vortex/doughnut beam, revealing unexpected excitations. Furthermore, the study demonstrates the transfer of the beam’s chirality to the internal and external motion of the atom, as evidenced by alterations in allowed atomic transitions. The research showcases the ability of both intrinsic (polarization) and extrinsic (orbital/structural) angular momentum of the beam to influence the atom, resulting in the transfer of two units of angular momentum. Notably, structured beams induce motion transversal to their propagation direction. The paper concludes with a position-resolved measurement of the azimuthal Doppler shift of a structured beam, uncovering its characteristic divergence at the center and its scale-invariant nature. These findings offer valuable insights into the understanding of structured beam-atom interactions, potentially constituting the first indirect observation of the elusive super-kicks predicted by Barnett and Berry in 2013.
Quantum teleportation relies on entanglement as the quantum resource to be able to communicate with fidelities beyond the classical limit. Nevertheless, the entangled resource may be afflicted by local noise, affecting its ability to serve as the entangled resource for quantum teleportation. We obtain experimental data on the influence of different local environments on the ability of an initially entangled pair of qubits to act as a teleportation resource, after it has been disturbed by noise. We generate selected conditions on the noise parameter space, both theoretically and experimentally, and we find that an already noisy protocol can be made practically insensitive to a further addition of noise. The experimental results are based on a photonic implementation of the quantum teleportation algorithm, with a polarization-entangled pair acting as the quantum resource. The state to be teleported is an additional qubit encoded in the path internal degree of freedom of Alice's photon. Interactions with different local environments on both sides of the system are either implemented with an extra qubit as the environment, or simulated as a weighed average of pure states. We compare our experimental results with the theoretical predictions, and by performing quantum process tomography we can calculate the fidelity of the quantum teleportation scheme and evaluate the effect of local environments.
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