Quantum dynamics of a mobile spin impurity

Abstract

One of the elementary processes in quantum magnetism is the propagation of spin excitations. Here we study the quantum dynamics of a deterministically created spin-impurity atom, as it propagates in a one-dimensional lattice system. We probe the spatial probability distribution of the impurity at different times using single-site-resolved imaging of bosonic atoms in an optical lattice. In the Mott-insulating regime, the quantum-coherent propagation of a magnetic excitation in the Heisenberg model can be observed using a post-selection technique. Extending the study to the superfluid regime of the bath, we quantitatively determine how the bath affects the motion of the impurity, showing evidence of polaronic behaviour. The experimental data agree with theoretical predictions, allowing us to determine the effect of temperature on the impurity motion. Our results provide a new approach to studying quantum magnetism, mobile impurities in quantum fluids and polarons in lattice systems

Toolbox for linear optics in a one-dimensional lattice via minimal control

“…Our scheme do not require an active atomic transport with external potential, while it exploits the natural atom dynamics (the quantum walk). Ultracold atoms in optical lattices are the most natural realization in view of recent unprecedented improvements in initialization and measurements [9][10][11]45]. In particular, compared to purely photonic setups, opening up this alternative arena for linear optics can have the advantages of Fock-state (e.g.…”

“…This quantity is experimentally accessible in an optical lattice implementation [9][10][11]. In the specific, in Ref.…”

“…Once in the Mott insulating phase, the system can be initialized via single site addressing in a state with a few localised particles, and the dynamics of a single traveling particle [11] and of two (interacting) particles [9,10] can be observed. State preparation fidelity is around 98% while single atom detection is possible with efficiency around 99% [50,51].…”

“…The recent atomic realization of a controlled beam splitter in a double well potential [8] highlights the importance of atomic linear optics. This, and the recent unprecedented abilities to initialize and measure the positions of individual atoms [9][10][11][12], raise the intriguing question: can we use a many-site lattice for performing arbitrary linear-optics operations? Large lattices are indeed required for many applications, such as boson sampling where the complexity increases dramatically when the number sites is much larger than the number of particles.…”

Quantum simulators by design: Many-body physics in reconfigurable arrays of tunnel-coupled traps

“…The recent invention of quantum gas microscopes [4,5] extended this work to the observation of local properties, such as spreading of correlations [6], dynamics of spin impurities [7], quantum walks [8], and entanglement entropy [9]. Although these setups allow for local modifications of the potential surface and the atom properties using holographic masks [4], spatial light modulators [7,8] or tightly focused laser beams [10], the underlying lattice structure remains periodic.…”