News: Research Highlights

Fri January 1, 2010

A Magnetic Gas

For decades, it has been an open question whether it is possible for a gas to show properties similar to a magnet made of iron or nickel.  Iron and nickel are ferromagnetic because they become strongly magnetized below a specific temperature, when unpaired electrons within the material spontaneously align in the same direction.

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Thu January 1, 2009

Alkaline-Earth-Metal Atoms as Few Qubit Quantum Registers

Gorshkov, A. M. Rey, A. J. Daley, M. M. Boyd, J. Ye, P. Zoller, and M. D. Lukin, Alkaline-Earth-Metal Atoms as Few Qubit Quantum Registers, Phys. Rev. Lett. 102, 110503 (2009).
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Thu January 1, 2009

When one electron is not enough ….

Most research involving ultra-cold matter has been done with atoms with one active electron (i.e. an electron outside a closed shell of electrons).  New theoretical work by CUA researchers has demonstrated that atoms with two active electrons (the so called alkaline-earth atoms)

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Thu January 1, 2009

Universal resource state for One-Way Quantum Computations

A fascinating model for quantum computing, other than the traditional quantum circuit model, is the “one-way” model that is based on simply doing single qubit measurements to a fixed, initial entangled quantum state of many qubits.  By feeding back measurement results to control the axis of subsequent measurements, any quantum circuit can be simulated and...
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Thu January 1, 2009

Preparation of decoherence-free cluster states with optical superlattices

L. Jiang, A. M. Rey, O. Romero-Isart, J. J. Garcia-Ripoli, A. Sampera, and M. D. Lukin, Preparation of decoherence-free cluster states with optical superlattices, Phys. Rev. A 79, 022309 (2009).
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Thu January 1, 2009

Realization of high selectivity ion qubit addressing scheme

Selectively addressing individual qubits in an array of ions is a vital task for scalable quantum computation with trapped ions.  Traditionally, this is accomplished using complex optics for laser beam steering, but such schemes are not easily scalable.  We have realized a scalable alternative which employs the advantages of microfabrication and cryogenic operation, and applies...
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Thu January 1, 2009

Realization of coherent optically dense media via buffer-gas cooling

T. Hong, A. Gorshkov, D. Patterson, A. S. Zibrov, J. M. Doyle, M. D. Lukin, and M. G. Prentiss, Realization of coherent optically dense media via buffer-gas cooling, Phys. Rev. A 79, 013806 (2009).
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Thu January 1, 2009

Swimming in the Fermi Sea

Our world is run by electrons. Whether we switch on a light, browse the internet or play music on the iPod, it is electrons moving through the wires, chips and headphones. But how do electrons actually get from A to B? After all, they have to get through a solid, a crystal maze of countless atoms. On their way through the solid, electrons push and pull nearby atoms around, attracting positive charges and repelling negative ones. It’s like an espalier, with arms flying high wherever the electron goes. These distortions in the crystal lattice thus closely follow the electron, and in fact the electron and the lattice deformations can be said to form a new entity or “quasi-particle”, called the polaron. Since the electron has to drag the lattice distortions with it, the polaron is heavier than an electron moving in empty space. That means a polaron is less inclined than a ‘bare’ electron to change its speed or direction of motion if someone pulls on it. Polarons are ubiquitous in solid state materials, they are crucial for the understanding of colossal magnetoresistance, and they are responsible for conduction in fullerenes and polymers.

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Thu January 1, 2009

Observartion of itinerant ferromagnetism in a strongly interacting Fermi gas of ultracold atoms

Ferromagnetism of delocalized (itinerant) fermions occurs due to repulsive interactions and the exchange energy which reduces the interaction energy for spin polarized domains due to the Pauli exclusion principle.  At a critical interaction, given by the so-called Stoner criterion [1], they system spontaneously develops domains and becomes ferromagnetic.  This, together with a suitable band structure...
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