Quantum Technologies

Frustrated Quantum Spin Models with Cold Coulomb Crystals

Date: 
2011-08-04
Author(s): 

A. Bermudez, J. Almeida, F. Schmidt-Kaler, A. Retzker, M. B. Plenio

Reference: 

arXiv:1108.1024 (2011)

We exploit the geometry of a zig-zag cold-ion crystal in a linear trap to propose the quantum simulation of a paradigmatic model of long-ranged magnetic frustration. Such a quantum simulation would clarify the complex features of a rich phase diagram that presents ferromagnetic, dimerized antiferromagnetic, paramagnetic, and floating phases, together with previously unnoticed features that are hard to assess by numerics. We analyze in detail its experimental feasibility, and provide supporting numerical evidence on the basis of realistic parameters in current ion-trap technology.

Fabrication of a segmented micro Penning trap and numerical investigations of versatile ion positioning protocols

Date: 
2011-06-28
Author(s): 

M. Hellwig, A. Bautista-Salvador, K. Singer, G. Werth, F. Schmidt-Kaler

Reference: 

New Journal of Physics 12, 065019 (2010)
doi:10.1088/1367-2630/12/6/065019

We describe a versatile planar Penning trap structure, which allows one to dynamically modify the trapping configuration almost arbitrarily. The trap consists of 37 hexagonal electrodes, each with a circumcircle diameter of 300 μm, fabricated in a gold-on-sapphire lithographic technique. Every hexagon can be addressed individually, thus shaping the electric potential. The fabrication of such a device with clean room methods is demonstrated.

Control of inhomogeneous atomic ensembles of hyperfine qudits

Date: 
2011-09-01
Author(s): 

Brian E. Mischuck, Seth T. Merkel, and Ivan H. Deutsch

Reference: 

arXiv:1109.0146v1

We study the ability to control d-dimensional quantum systems (qudits) encoded in the hyperfine spin of alkali-metal atoms through the application of radio- and microwave-frequency magnetic fields in the presence of inhomogeneities in amplitude and detuning. Such a capability is essential to the design of robust pulses that mitigate the effects of experimental uncertainty and also for application to tomographic addressing of particular members of an extended ensemble. We study the problem of preparing an arbitrary state in the Hilbert space from an initial fiducial state.

UNIBAS as a new partner in the AQUTE Consortium

Summary: 

Universität Basel (UNIBAS) is a new partner in the AQUTE Consortium

On the 4th of February 2011 the European Commission has sent us the official approval to our request to add Basel Universität (UNIBAS) among the AQUTE partners, following the move of Professor Philipp Treutlein from München (LMU, AQUTE partner P11) to Basel.

Detecting phonon blockade with photons

Date: 
2011-08-04
Author(s): 

N. Didier, S. Pugnetti, Y. M. Blanter, and R. Fazio

Reference: 

Phys. Rev. B 84, 054503 (2011)

Measuring the quantum dynamics of a mechanical system, when few phonons are involved, remains a challenge. We show that a superconducting microwave resonator linearly coupled to the mechanical mode constitutes a very powerful probe for this scope. This new coupling can be much stronger than the usual radiation pressure interaction by adjusting a gate voltage. We focus on the detection of phonon blockade, showing that it can be observed by measuring the statistics of the light in the cavity. The underlying reason is the formation of an entangled state between the two resonators.

Adiabatically steered open quantum systems: Master equation and optimal phase

Date: 
2010-12-14
Author(s): 

J. Salmilehto, P. Solinas, J. Ankerhold, and M. Möttönen

Reference: 

Phys. Rev. A 82, 062112 (2010)

We introduce an alternative way to derive the generalized form of the master equation recently presented by J. P. Pekola et al. Phys. Rev. Lett. 105 030401 (2010) for an adiabatically steered two-level quantum system interacting with a Markovian environment. The original derivation employed the effective Hamiltonian in the adiabatic basis with the standard interaction picture approach but without the usual secular approximation. Our approach is based on utilizing a master equation for a nonsteered system in the first superadiabatic basis.

Real-time quantum feedback prepares and stabilizes photon number states

Date: 
2011-09-01
Author(s): 

C. Sayrin, I. Dotsenko, X. Zhou, B. Peaudecerf, T. Rybarczyk, S. Gleyzes, P. Rouchon, M. mirrahimi, H. Amini, M. Brune, J.M. Raimond, S. Haroche

Reference: 

Nature (London) 477, 73 (2011)
doi: 10.1038/nature10376

Feedback loops are central to most classical control procedures. A controller compares the signal measured by a sensor (system output) with the target value or set-point. It then adjusts an actuator (system input) to stabilize the signal around the target value. Generalizing this scheme to stabilize a micro-system’s quantum state relies on quantum feedback, which must overcome a fundamental difficulty: the sensor measurements cause a random back-action on the system. An optimal compromise uses weak measurements, providing partial information with minimal perturbation.

Entanglement Storage Units

Date: 
2011-08-16
Author(s): 

T. Caneva, T. Calarco, S. Montangero

Reference: 

New J. Phys. 14 093041 (2012)

We introduce a protocol to drive many body quantum systems into long-lived entangled states, protected from decoherence by big energy gaps. With this approach it is possible to implement scalable entanglement-storage units. We test the protocol in the Lipkin-Meshkov-Glick model, a prototype many-body quantum system that describes different experimental setups.

SQR Technologies

Website: 

SQR Technologies is a young and dynamic startup in preparation since 2007 and founded in 2010. It is a spinoff of the ULB's Centre for Quantum Information and Communication. SQR specializes in hardware security for datacenters with the mission to develop the next platform of cloud security solutions by exploiting the laws of quantum physics. 

Dark States of Single Nitrogen-Vacancy Centers in Diamond Unraveled by Single Shot NMR

Date: 
2011-04-14
Author(s): 

G. Waldherr, J. Beck, M. Steiner, P. Neumann, A. Gali, T. Fraunheim, F. Jelezko, J. Wrachtrup

Reference: 

PHYSICAL REVIEW LETTERS Volume: 106 Issue: 15 Article Number: 157601 DOI: 10.1103/PhysRevLett.106.157601

The nitrogen-vacancy (NV) center in diamond is supposed to be a building block for quantum computing and nanometer-scale metrology at ambient conditions. Therefore, precise knowledge of its quantum states is crucial. Here, we experimentally show that under usual operating conditions the NV exists in an equilibrium of two charge states [70% in the expected negative (NV-) and 30% in the neutral one (NV0)].

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