Perfect initialization of a quantum computer of neutral atoms in an optical lattice of large lattice constant

We propose a scheme for the initialization of a quantum computer based on neutral atoms trapped in an optical lattice with large lattice constant. Our focus is the development of a compacting scheme to prepare a perfect optical lattice of simple orthorhombic structure with unit occupancy. Compacting is accomplished by sequential application of two types of operations: a flip operator that changes the internal state of the atoms, and a shift operator that moves them along the lattice principal axis. We propose physical mechanisms for realization of these operations and we study the effects of motional heating of the atoms. We carry out an analysis of the complexity of the compacting scheme and show that it scales linearly with the number of lattice sites per row of the lattice, thus showing good scaling behavior with the size of the quantum computer.Comment: 18 page

Local symmetry properties of pure 3-qubit states

Entanglement types of pure states of 3 qubits are classified by means of their stabilisers in the group of local unitary operations. It is shown that the stabiliser is generically discrete, and that a larger stabiliser indicates a stationary value for some local invariant. We describe all the exceptional states with enlarged stabilisers.Comment: 32 pages, 5 encapsulated PostScript files for 3 figures. Published version, with minor correction

Meteorite falls over India during 2003: Petrographic and chemical characterization and cosmogenic records

Two meteorite falls observed over India in 2003 led to the recovery of surviving fragments. The Kasauli meteorite that fell in northern India is a single fall, while Kendrapara meteorite is a multiple fall that covered a large coastal region of Orissa. Data for petrographic characteristics and chemical composition suggest that the two meteorites belong to the H group of chondrites, with Kasuali suffering a lesser degree of thermal metamorphism than Kendrapara during their residence in their parent bodies. Cosmogenic records indicate a large size (≥1 m) for the Kendrapara meteoroid that has spent ~5 million years in interplanetary space following its ejection from its parent body until its fall on the Earth. On the other hand, the Kasauli meteoroid spent an unusually long time (~37 Ma) in interplanetary space before its fall and lost ~80% of its original mass during atmospheric ablation

Multipartite entanglement for entanglement teleportation

The scheme for entanglement teleportation is proposed to incorporate multipartite entanglement of four qubits as a quantum channel. Based on the invariance of entanglement teleportation under arbitrary two-qubit unitary transformation, we derive relations of separabilities for joint measurements at a sending station and for unitary operations at a receiving station. From the relations of separabilities it is found that an inseparable quantum channel always leads to a total teleportation of entanglement with an inseparable joint measurement and/or a nonlocal unitary operation.Comment: slightly modifie

Entangled Rings

Consider a ring of N qubits in a translationally invariant quantum state. We ask to what extent each pair of nearest neighbors can be entangled. Under certain assumptions about the form of the state, we find a formula for the maximum possible nearest-neighbor entanglement. We then compare this maximum with the entanglement achieved by the ground state of an antiferromagnetic ring consisting of an even number of spin-1/2 particles. We find that, though the antiferromagnetic ground state does not maximize the nearest-neighbor entanglement relative to all other states, it does so relative to other states having zero z-component of spin.Comment: 19 pages, no figures; v2 includes new results; v3 corrects a numerical error for the case N=

Scheme for the preparation of the multi-particle entanglement in cavity QED

Here we present a quantum electrodynamics (QED) model involving a large-detuned single-mode cavity field and $n$ identical two-level atoms. One of its applications for the preparation of the multi-particle states is analyzed. In addition to the Greenberger-Horne-Zeilinger (GHZ) state, the W class states can also be generated in this scheme. The further analysis for the experiment of the model of $n=2$ case is also presented by considering the possible three-atom collision.Comment: 5 Pages, 1 Figure. Minor change

Strong subadditivity inequality for quantum entropies and four-particle entanglement

Strong subadditivity inequality for a three-particle composite system is an important inequality in quantum information theory which can be studied via a four-particle entangled state. We use two three-level atoms in $\Lambda$ configuration interacting with a two-mode cavity and the Raman adiabatic passage technique for the production of the four-particle entangled state. Using this four-particle entanglement, we study for the first time various aspects of the strong subadditivity inequality.Comment: 5 pages, 3 figures, RevTeX4, submitted to PR

Non-local Operations: Purification, storage, compression, tomography, and probabilistic implementation

We provide several applications of a previously introduced isomorphism between physical operations acting on two systems and entangled states [1]. We show: (i) how to implement (weakly) non-local two qubit unitary operations with a small amount of entanglement; (ii) that a known, noisy, non-local unitary operation as well as an unknown, noisy, local unitary operation can be purified; (iii) how to perform the tomography of arbitrary, unknown, non-local operations; (iv) that a set of local unitary operations as well as a set of non-local unitary operations can be stored and compressed; (v) how to implement probabilistically two-qubit gates for photons. We also show how to compress a set of bipartite entangled states locally, as well as how to implement certain non-local measurements using a small amount of entanglement. Finally, we generalize some of our results to multiparty systems.Comment: 15 pages, no figure