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Fast quantum gate via Feshbach-Pauli blocking in a nanoplasmonic trap

Date: 
2014-06-25 - 2014-11-27
Author(s): 

K. Jachymski, Z. Idziaszek, T. Calarco

Reference: 

DOI: 10.1103/PhysRevLett.112.250502
Journal reference: Phys. Rev. Lett. 112, 250502 (2014)

We propose a simple idea for realizing a quantum gate with two identical fermions in a double well trap via external optical pulses without addressing the atoms individually. The key components of the scheme are Feshbach resonance and Pauli blocking, which decouple unwanted states from the dynamics.

Interferometry with non-classical motional states of a Bose–Einstein condensate

Date: 
2014-05-30 - 2014-11-27
Author(s): 

S. van Frank, A. Negretti, T. Berrada, R. Bücker, S. Montangero, J.-F.
Schaff, T. Schumm, T. Calarco, J. Schmiedmayer

Reference: 

Journal reference: Nature Communications 5, 4009 (2014)
DOI: 10.1038/ncomms5009
Cite as: arXiv:1402.0377 [quant-ph]

We demonstrate a two-pulse Ramsey-type interferometer for non-classical motional states of a Bose-Einstein condensate in an anharmonic trap. The control pulses used to manipulate the condensate wavefunction are obtained from Optimal Control Theory and directly optimised to maximise the interferometric contrast.

Matrix-Product Operators and States: NP-Hardness and Undecidability

Date: 
2014-10-16
Author(s): 

M. Kliesch, D. Gross, and J. Eisert

Reference: 

Phys. Rev. Lett. 113 (2014); DOI: http://dx.doi.org/10.1103/PhysRevLett.113.160503

Tensor network states constitute an important variational set of quantum states for numerical studies of strongly correlated systems in condensed-matter physics, as well as in mathematical physics. This is specifically true for finitely correlated states or matrix-product operators, designed to capture mixed states of one-dimensional quantum systems.

Quantum error correction in a solid-state hybrid spin register

Date: 
2014-02-13
Author(s): 

G. Waldherr, Y. Wang, S. Zaiser, M. Jamali, T. Schulte-Herbrüggen, H. Abe, T. Ohshima, J. Isoya, J.F. Du, P. Neumann, J. Wrachtrup

Reference: 

Nature 506, 204 (2014)

Error correction is important in classical and quantum computation. Decoherence caused by the inevitable interaction of quantum bits with their environment leads to dephasing or even relaxation. Correction of the concomitant errors is therefore a fundamental requirement for scalable quantum computation. Although algorithms for error correction have been known for some time, experimental realizations are scarce. Here we show quantum error correction in a heterogeneous, solid-state spin system.

Homodyne Tomography of a Single Photon Retrieved on Demand from a Cavity-Enhanced Cold Atom Memory

Date: 
2014-01-21
Author(s): 

Erwan Bimbard, Rajiv Boddeda, Nicolas Vitrant, Andrey Grankin, Valentina Parigi, Jovica Stanojevic, Alexei Ourjoumtsev, and Philippe Grangier

Reference: 

Bimbard, R. Boddeda, N. Vitrant, A. Grankin, V. Parigi, J. Stanojevic, A. Ourjoumtsev, P. Grangier, Homodyne Tomography of a Single Photon Retrieved on Demand from a Cavity-Enhanced Cold Atom Memory, PHYSICAL REVIEW LETTERS 112:3, 033601 (2014)
DOI: 10.1103/PhysRevLett.112.033601

We experimentally demonstrate that a nonclassical state prepared in an atomic memory can be efficiently transferred to a single mode of free-propagating light. By retrieving on demand a single excitation from a cold atomic gas, we realize an efficient source of single photons prepared in a pure, fully controlled quantum state. We characterize this source using two detection methods, one based on photon-counting analysis and the second using homodyne tomography to reconstruct the density matrix and Wigner function of the state.

Broadband single-photon-level memory in a hollow-core photonic crystal fibre

Date: 
2014-05-26
Author(s): 

M. R. Sprague, P. S. Michelberger, T. F. M. Champion, D. G. England, J. Nunn, X.-M. Jin, W. S. Kolthammer, A. Abdolvand, P. St. J. Russell & I. A. Walmsley

Reference: 

Nature Photonics 8, 287–291 (2014)

doi:10.1038/nphoton.2014.45

Storing information encoded in light is critical for realizing optical buffers for all-optical signal processing

Macroscopic Optomechanics from Displaced Single-Photon Entanglement

Date: 
2014-02-27 - 2014-05-12
Author(s): 

Pavel Sekatski, Markus Aspelmeyer, Nicolas Sangouard

Reference: 

Phys. Rev. Lett. 112, 080502 (2014)

Displaced single-photon entanglement is a simple form of optical entanglement, obtained by sending a photon on a beamsplitter and subsequently applying a displacement operation.

Nonlinear interaction between two heralded single photons

Date: 
2014-05-12
Author(s): 

T. Guerreiro, A. Martin, B. Sanguinetti, J. S. Pelc, C. Langrock, M. M. Fejer, N. Gisin, H. Zbinden, N. Sangouard, R. T. Thew

Reference: 

arXiv:1403.2084 (2014)

Harnessing nonlinearities strong enough to allow two single photons to interact with one another is not only a fascinating challenge but is central to numerous advanced applications in quantum information science. Currently, all known approaches are extremely challenging although a few have led to experimental realisations with attenuated classical laser light.

Heralded Single-Phonon Preparation, Storage, and Readout in Cavity Optomechanics

Date: 
2014-04-09 - 2014-05-09
Author(s): 

Christophe Galland, Nicolas Sangouard, Nicolas Piro, Nicolas Gisin, and Tobias J. Kippenberg

Reference: 

Physical Review Letters 112, 143602 – Published 9 April 2014

We show how to use the radiation pressure optomechanical coupling between a mechanical oscillator and an optical cavity field to generate in a heralded way a single quantum of mechanical motion (a Fock state). Starting with the oscillator close to its ground state, a laser pumping the upper motional sideband produces correlated photon-phonon pairs via optomechanical parametric down-conversion.

Edge Theories in Projected Entangled Pair State Models

Date: 
2014-01-23
Author(s): 

S. Yang, L. Lehman, D. Poilblanc, K. Van Acoleyen, F. Verstraete, J. I. Cirac, and N. Schuch

Reference: 

Phys. Rev. Lett. 112, 036402

We analyze the low energy excitations of spin lattice systems in two dimensions at zero temperature within the framework of projected entangled pair state models. Perturbations in the bulk give rise to physical excitations located at the edge.

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