Highlight

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.

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 single photons

Date: 
2014-10-24
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: 

PRL 113, 173601 (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.

Observation of Quantized Conductance in Neutral Matter

Date: 
2015-01-08
Author(s): 

Sebastian Krinner, David Stadler, Dominik Husmann, Jean-Philippe Brantut, Tilman Esslinger

Reference: 

Nature 517, 64-67 (2015)

In transport experiments the quantum nature of matter becomes directly evident when changes in conductance occur only in discrete steps, with a size determined solely by Planck's constant h. The observations of quantized steps in the electric conductance have provided important insights into the physics of mesoscopic systems and allowed for the development of quantum electronic devices. Even though quantized conductance should not rely on the presence of electric charges, it has never been observed for neutral, massive particles.

Deterministic quantum teleportation with feed-forward in a solid state system

L. Steffen, Y. Salathe, M. Oppliger, P. Kurpiers, M. Baur, C. Lang, C. Eichler, G. Puebla-Hellmann, A. Fedorov and A. Wallraff.
Nature 500, 319-322 (2013)

Demonstrations of primitive information processing elements with quantum bits (qubits) have been
implemented in many systems, but the requirements for precise quantum control, along with fast classical
feed-forward (conditioning future operations on measurement results) has proved challenging.

Room-Temperature Quantum Bit Storage Exceeding 39 Minutes Using Ionized Donors in Silicon-28

K. Saeedi, S. Simmons, J. Z. Salvail, P. Dluhy, H. Riemann, N. V. Abrosimov, P. Becker, H.-J. Pohl, J. L. Morten and M. L. W. Thewalt
Science 342, 830-833 (2013)

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