Nature (London) 477, 73 (2011)
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.
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 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.
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)].
NATURE PHYSICS Volume: 7 Issue: 6 Pages: 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.
A symposium "Quantum metrology with photons and atoms" will be held on the occasion of the 10th anniversary of National Laboratory for Atomic, Molecular and Optical Physics on the 17th September 2011 in Toruń, Poland.
The Laboratory for Atomic, Molecular and Optical Physics in Toruń is a national consortium involving among other institutions University of Warsaw, a partner in the Q-ESSENCE project. One of the themes of the symposium will be quantum-enhanced metrology. The meeting will provide a platform to exchange ideas and recent development with other sub-fields of modern metrology.
For further information please visit the event's website: http://famo.fizyka.umk.pl/qmet/.
The Q-ESSENCE project meeting will take place during the QIPC 2011 conference in Zurich. The exact time is 16:30-18:50 on the Friday 9th September 2011. A joint dinner will follow afterwards.
M. Roncaglia, M. Rizzi & J. Dalibard
From rotating atomic rings to quantum Hall states
Scientific Reports 1, 43 (2011)
Considerable efforts are currently devoted to the preparation of ultracold neutral atoms in the strongly correlated quantum Hall regime. However, the necessary angular momentum is very large and in experiments with rotating traps this means spinning frequencies extremely near to the deconfinement limit; consequently, the required control on parameters turns out to be too stringent. Here we propose instead to follow a dynamic path starting from the gas initially confined in a rotating ring.
Phys. Rev. Lett. 106, 230404 (2011).
We study the single particle dynamics of a mobile non-Abelian anyon hopping around many pinned anyons on a surface, by modeling it with a discrete time quantum walk. During the evolution, the spatial degree of freedom of the mobile anyon becomes entangled with the fusion degrees of freedom of the collective system. Each quantum trajectory makes a closed braid on the world lines of the particles establishing a direct connection between statistical dynamics and quantum link invariants.
Eindhoven University of Technology, a partner in Q-ESSENCE consortium, organizes the International Workshop on Nanowire Superconducting Single-Photon Detectors.
This one-day workshop on the physics, technology and application of single-photon detectors based on superconducting nanowires will take place on Friday September 23, 2011, in Eindhoven, The Netherlands. It will be a satellite workshop of the EUCAS 2011 - Superconductivity Centennial Conference (The Hague, September 18-23).