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arXiv:1212.4382

An optically resolvable Schrödinger's cat from Rydberg dressed cold atom clouds

S. Möbius, Michael Genkin, Alexander Eisfeld, Sebastian Wüster, Jan Michael Rost

Published Dec 18, 2012• 0 citations
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Abstract

In Rydberg dressed ultra-cold gases, ground state atoms inherit properties of a weakly admixed Rydberg state, such as sensitivity to long-range interactions. We show that through hyperfine-state dependent interactions, a pair of atom clouds can evolve into a spin and subsequently into a spatial Schrödinger's cat state: The pair, containing 20 atoms in total, is in a coherent superposition of two configurations, with cloud locations separated by micrometers. The mesoscopic nature of the superposition state can be proven with absorption imaging, while the coherence can be revealed though recombination and interference of the split wave packets.

DOI
10.48550/arxiv.1212.4382

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In Rydberg dressed ultra-cold gases, ground state atoms inherit properties of a weakly admixed Rydberg state, such as sensitivity to long-range interactions. We show that through hyperfine-state dependent interactions, a pair of atom clouds can evolve into a spin and subsequently into a spatial Schrödinger's cat state: The pair, containing 20 atoms in total, is in a coherent superposition of two configurations, with cloud locations separated by micrometers. The mesoscopic nature of the superposition state can be proven with absorption imaging, while the coherence can be revealed though recombination and interference of the split wave packets.
In Rydberg dressed ultracold gases, ground-state atoms inherit properties of a weakly admixed Rydberg state, such as sensitivity to long-range interactions. We show that through hyperfine-state-dependent interactions, a pair of atom clouds can evolve into a spin and subsequently into a spatial mesoscopic superposition state: The pair is in a coherent superposition of two configurations, with cloud locations separated by micrometers. The mesoscopic nature of the state can be proven with absorption imaging, while the coherence can be revealed though recombination and interference of the split wave packets.
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We consider two clouds of ground-state alkali atoms in two distinct hyperfine ground states. Each level is far off-resonantly coupled to a Rydberg state, which leads to dressed ground states with a weak admixture of the Rydberg state properties. Due to this admixture, for a proper choice of the Rydberg states, the atoms experience resonant dipole–dipole interactions that induce mechanical forces acting on all atoms within both clouds. This behaviour is in contrast to the dynamics predicted for bare dipole–dipole interactions between Rydberg superatoms, where only a single atom per cloud is subject to dipole–dipole induced motion (Möbius et al 2013 Phys. Rev. A 88 012716).
We discuss techniques to generate long-range interactions in a gas of ground state alkali atoms, by weakly admixing excited Rydberg states with laser light. This provides a tool to engineer strongly correlated phases with reduced decoherence from inelastic collisions and spontaneous emission. As an illustration, we discuss the quantum phases of dressed atoms with dipole-dipole interactions confined in a harmonic potential, as relevant to experiments. We show that residual spontaneous emission from the Rydberg state acts as a heating mechanism, leading to a quantum-classical crossover.
A "Schrodinger cat"-like state of matter was generated at the single atom level. A trapped 9Be+ ion was laser-cooled to the zero-point energy and then prepared in a superposition of spatially separated coherent harmonic oscillator states. This state was created by application of a sequence of laser pulses, which entangles internal (electronic) and external (motional) states of the ion. The Schrodinger cat superposition was verified by detection of the quantum mechanical interference between the localized wave packets. This mesoscopic system may provide insight into the fuzzy boundary between the classical and quantum worlds by allowing controlled studies of quantum measurement and quantum decoherence.
We study atoms in optical lattices whose electronic ground state is off-resonantly coupled to a highly excited state with strong binary interactions. We present a time-dependent treatment of the resulting quantum dynamics, which---contrary to recent predictions [Li, Ates, and Lesanovsky, Phys. Rev. Lett. 110, 213005 (2013)]---proves that the strong repulsion between the weakly admixed Rydberg states does not lead to atomic trap loss. This finding provides an important basis for creating and manipulating coherent long-range interactions in optical lattice experiments.