Quantum Computation

Call For Conference Proposals published

Summary: 

A call for proposals for the next QUIE2T sponsored QIPC conference has been published.

A call for proposals for the next QUIE2T sponsored QIPC conference has been published.

Holonomic quantum computing in ground states of spin chains with symmetry-protected topological order

Date: 
2011-03-30
Author(s): 

M. Renes, Akimasa Miyake, Gavin K. Brennen, and Stephen D. Bartlett

Reference: 

arxiv:1103.5076

While solid-state devices offer naturally reliable hardware for modern classical computers, thus far quantum information processors resemble vacuum tube computers in being neither reliable nor scalable. Strongly correlated many body states stabilized in topologically ordered matter offer the possibility of naturally fault tolerant computing, but are both challenging to engineer and coherently control and cannot be easily adapted to different physical platforms.

Quantum Information Team, LTCI, Telecom ParisTech

Website: 
Research Type: 
Theory
Experiment

 - Quantum key distribution with continuous variables: theoretical and experimental work on long-distance system performance and side channel induced attacks

- Quantum cryptographic primitives: theoretical and experimental work on secret sharing, coin flipping, entanglement verification in the presence of adversaries

- Theory of Quantum Computation and Quantum Information including measurement-based quantum computing, entanglement theory and foundations of physics

Leader: 
Romain Alléaume, Eleni Diamanti, Damian Markham, Isabelle Zaquine

Prospects for fast Rydberg gates on an atom chip

Date: 
2011-11-03
Author(s): 

M. M. Müller, H. R. Haakh, T. Calarco, C. P. Koch and C. Henkel

Reference: 

Quantum Inf. Process. 10, 771 (2011). From the issue entitled "Special Issue on Neutral Particles".

Atom chips are a promising candidate for a scalable architecture for quantum information processing provided a universal set of gates can be implemented with high fidelity. The difficult part in achieving universality is the entangling two-qubit gate. We consider a Rydberg phase gate for two atoms trapped on a chip and employ optimal control theory to find the shortest gate that still yields a reasonable gate error. Our parameters correspond to a situation where the Rydberg blockade regime is not yet reached.

Electric-field sensing using single diamond spins

Date: 
2011-04-17
Author(s): 

F. Dolde, H. Fedder, M. Doherty, T. Nöbauer, F. Rempp, G. Balasubramanian, T. Wolf, F. Reinhard, L. Hollenberg, F. Jelezko, J. Wrachtrup

Reference: 

Nature Physics, 7 (2011), pp 459 - 463
doi:10.1038/nphys1969

The ability to sensitively detect individual charges under ambient conditions would benefit a wide range of applications across disciplines. However, most current techniques are limited to low-temperature methods such as single-electron transistors, single-electron electrostatic force microscopy and scanning tunnelling microscopy. Here we introduce a quantum-metrology technique demonstrating precision three-dimensional electric-field measurement using a single nitrogen-vacancy defect centre spin in diamond. An a.c.

Implementing the Quantum von Neumann Architecture with Superconducting Circuits

Date: 
2011-10-07
Author(s): 

Matteo Mariantoni, H. Wang, T. Yamamoto, M. Neeley1, Radoslaw C. Bialczak, Y. Chen, M. Lenander, Erik Lucero, A. D. O’Connell, D. Sank, M. Weides, J. Wenner, Y. Yin, J. Zhao, A. N. Korotkov, A. N. Cleland, John M. Martinis

Reference: 

Science Vol. 334 no. 6052 pp. 61-65. DOI: 10.1126/science.1208517

The von Neumann architecture for a classical computer comprises a central processing unit and a memory holding instructions and data. We demonstrate a quantum central processing unit that exchanges data with a quantum random-access memory integrated on a chip, with instructions stored on a classical computer. We test our quantum machine by executing codes that involve seven quantum elements: Two superconducting qubits coupled through a quantum bus, two quantum memories, and two zeroing registers.

Atom Counting in Expanding Ultracold Clouds

Date: 
2011-03-09
Author(s): 

S. Braungardt, M. Rodríguez, A. Sen De, U. Sen, M. Lewenstein

Reference: 

arXiv:1103.1868

We study the counting statistics of ultracold bosonic atoms that are released from an optical lattice. We show that the counting probability distribution of the atoms collected at a detector located far away from the optical lattice can be used as a method to infer the properties of the initially trapped states. We consider initial superfluid and insulating states with different occupation patterns. We analyze how the correlations between the initially trapped modes that develop during the expansion in the gravitational field are reflected in the counting distribution.

Quantum simulation of frustrated classical magnetism in triangular optical lattices

Date: 
2011-07-21
Author(s): 

J. Struck, C. Ölschläger, R. Le Targat, P. Soltan-Panahi, A. Eckardt, M. Lewenstein, P. Windpassinger, K. Sengstock

Reference: 

Science 333, 996-999 (2011)

Magnetism plays a key role in modern technology and stimulates research in several branches of condensed matter physics. Although the theory of classical magnetism is well developed, the demonstration of a widely tunable experimental system has remained an elusive goal. Here, we present the realization of a large-scale simulator for classical magnetism on a triangular lattice by exploiting the particular properties of a quantum system.

Quantum Memory Assisted Probing of Dynamical Spin Correlations

Date: 
2011-05-31
Author(s): 

O. Romero-Isart, M. Rizzi, C. A. Muschik, E. S. Polzik, M. Lewenstein, A. Sanpera

Reference: 

arXiv:1105.6308

We propose a method to probe dynamical spin correlations of strongly interacting systems in optical lattices. The scheme uses a light-matter quantum non-demolition interface to map consecutively a given non trivial magnetic observable of the strongly correlated system to the light. The quantum memory is essential to coherently store the previously mapped observable during a time scale comparable to the many-body dynamics. A final readout of the memory yields direct access to dynamical correlations.

Can One Trust Quantum Simulators?

Date: 
2012-07-26
Author(s): 

P. Hauke, F. M. Cucchietti, L. Tagliacozzo, M. Lewenstein, I. Deutsch

Reference: 

arXiv:1109.6457

arXiv:1109.6457v3 [quant-ph]

Various quantum phenomena like high-Tc superconductivity or quark confinement are still awaiting universally accepted explanations, because of the computational complexity of solving simplified theoretical models designed to capture their relevant physics. Feynman suggested solving such models by "quantum simulation" with a device designed to obey the same quantum many-body dynamics. So far, the community has mostly focused on developing the \emph{controllability} of quantum simulators.

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