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arXiv:0803.1643 · Physical Review A

Quantum many-body dynamics of coupled double-well superlattices

Peter Barmettler, Ana María Rey, Eugene Demler, Mikhail D. Lukin, Immanuel Bloch, Vladimir Gritsev

Published Jul 17, 2008• 72 citations
arXivHTMLPDF

Abstract

We propose a method for controllable generation of nonlocal entangled pairs using spinor atoms loaded in an optical superlattice. Our scheme iteratively increases the distance between entangled atoms by controlling the coupling between the double wells. When implemented in a finite linear chain of $2N$ atoms, it creates a triplet valence bond state with large persistency of entanglement (of the order of $N$). We also study the nonequilibrium dynamics of the one-dimensional ferromagnetic Heisenberg Hamiltonian and show that the time evolution of a state of decoupled triplets on each double well leads to the formation of a highly entangled state where short-distance antiferromagnetic correlations coexist with longer-distance ferromagnetic ones. We present methods for detection and characterization of the various dynamically generated states. These ideas are a step forward toward the use of atoms trapped by light as quantum-information processors and quantum simulators.

DOI
10.1103/physreva.78.012330

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We report on the controlled creation of a valence bond state of delocalized effective-spin singlet and triplet dimers by means of a bichromatic optical superlattice. We demonstrate a coherent coupling between the singlet and triplet states and show how the superlattice can be employed to measure the singlet-fraction employing a spin-blockade effect. Our method provides a reliable way to detect and control nearest-neighbor spin correlations in many-body systems of ultracold atoms. Being able to measure these correlations is an important ingredient in studying quantum magnetism in optical lattices. We furthermore employ a SWAP operation between atoms which are part of different triplets, thus effectively increasing their bond-length. Such a SWAP operation provides an important step towards the massively parallel creation of a multiparticle entangled state in the lattice.
Quantum simulations of Hubbard models with ultracold atoms rely on the exceptional control of coherent motion provided by optical lattices. Here we demonstrate enhanced tunability using an optical superlattice in a fermionic quantum gas microscope, evidenced by long-lived coherent double-well oscillations, next-nearest-neighbor quantum walks in a staggered configuration, and correlated quantum walks of two particles initiated through a resonant pair-breaking mechanism. We furthermore demonstrate tunable spin couplings through local offsets and engineer a spin ladder with ferromagnetic and antiferromagnetic couplings along the rungs and legs, respectively. Our Letter underscores the high potential of optical superlattices for engineering, simulating, and detecting strongly correlated many-body quantum states, with direct applications ranging from the study of mixed-dimensional systems to fermionic quantum computing.
We investigate how to create entangled states of ultracold atoms trapped in optical lattices by dynamically manipulating the shape of the lattice potential. We consider an additional potential (the superlattice) that allows both the splitting of each site into a double well potential, and control of the height of the potential barrier between sites. We use superlattice manipulations to perform entangling operations between neighbouring qubits encoded on the Zeeman levels of the atoms without having to perform transfers between the different vibrational states of the atoms. We show how to use superlattices to engineer many-body entangled states resilient to collective dephasing noise. Also, we present a method to realize a two-dimensional (2D) resource for measurement-based quantum computing via Bell-pair measurements. We analyse measurement networks that allow the execution of quantum algorithms while maintaining the resilience properties of the system throughout the computation.
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