Since the two qubits are encoded in identical bosons, the full two-particle wavefunction must be symmetric under particle exchange, e.g.,, where the two atoms are labelled 1 and 2. (In the merged trap, the subscripts L and R are replaced by e and g, , and an independent 1D lattice along the vertical direction. By controlling the laser polarization, the unit cell of the 2D lattice can be continuously changed between single-well (λ-lattice) or double-well (λ/2-lattice)configurations (see Fig. 1a), where λ=816 nm. We start with a magnetically trapped We can prepare every pair of atoms in any non-entangled two-qubit state by selectively addressing the atoms in the L and R sites. We exploit the spin-dependence of the potential, which can be manipulated through the same polarization control used to adjust the lattice topology 2,12 . We first induce a state-dependence in the optical potential that produces an effective magnetic field gradient between the two adjacent sites of the double well. This introduces a differential shift The > 10 ms decay of the swap oscillations in Fig. 3 , but there the underlying noise arises from the inherent fluctuating background of nuclear spins. In contrast, here the inhomogeneous broadening arises

Campbell, B. C.V. et al. (2019) Penumbral imaging and functional outcome in patients with anterior circulation ischaemic stroke treated with endovascular thrombectomy versus medical therapy: a meta-analysis of individual patient-level data.ABSTRACT Background: CT-perfusion (CTP) and MRI may assist patient selection for endovascular thrombectomy. We aimed to establish whether imaging assessments of ischaemic core and penumbra volumes were associated with functional outcomes and treatment effect.

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We describe the controlled loading and measurement of number-squeezed states and Poisson states of atoms in individual sites of a double well optical lattice. These states are input to an atom interferometer that is realized by symmetrically splitting individual lattice sites into double wells, allowing atoms in individual sites to evolve independently. The two paths then interfere, creating a matter-wave double-slit diffraction pattern. The time evolution of the double-slit diffraction pattern is used to measure the number statistics of the input state. The flexibility of our double well lattice provides a means to detect the presence of empty lattice sites, an important and so far unmeasured factor in determining the purity of a Mott state. The optical beam splitter, with its two input and two output modes, is one of the simplest examples of a two mode quantum system. At the quantum level this fundamental system has interesting, nonclassical behavior such as the quantum interference between correlated, indistinguishable photons [1]. This system becomes even richer when the particles interact. While photons may effectively interact in nonlinear media, the atom optics analog is naturally interacting. The two mode beam splitter has already been applied in atom optics experiments; several experiments have split a trapped Bose-Einstein condensate (BEC) by raising a barrier to separate the condensate into two independent condensates [2,3,4,5]. In these experiments the number of atoms is large, in a regime where few-particle quantum interference effects cannot be seen. Here we demonstrate a new few-atom quantum "beam splitter" [6] and use it to create and analyze classical and nonclassical states, resulting in interesting few-atom quantum effects. The ability to create and analyze such states provides a probe of many-body states in a lattice, a platform for fundamental studies of fewparticle, interacting systems, and is of paramount importance for quantum computation with neutral atoms.We realize an atomic analog of the optical two-mode quantum beam splitter with 87 Rb atoms loaded into an optical lattice of double wells [7]. This 3D lattice has a unit cell that can be dynamically transformed between single well and double well configurations (Fig. 1a). In analogy with the optical beam splitter, the input and output modes in this lattice are either the ground |g and first excited |e state of the single well or the ground state of the left |L and right |R sites of the double well. Dynamically switching between these two configurations effectively creates an array of "beam splitters" (BS) coupling these modes (in the limit that higher modes are not excited). The interactions between atoms and our control of the beam splitter time scale extends the possible actions beyond those of a traditional beam splitter.The speed at which the beam splitter is applied to the atoms determines whether interactions play a role in the splitting: if the BS is applied quickly compared to interaction energies, the interactions are unimport...