Search results for "Measurement"
showing 10 items of 2918 documents
Coherent control via weak measurements in P31 single-atom electron and nuclear spin qubits
2018
The understanding of weak measurements and interaction-free measurements has greatly expanded the conceptual and experimental toolbox to explore the quantum world. Here we demonstrate single-shot variable-strength weak measurements of the electron and nuclear spin states of a P31 single-atom donor in silicon. We first show how the partial collapse of the nuclear spin due to measurement can be used to coherently rotate the spin to a desired pure state. We explicitly demonstrate that phase coherence is preserved with high fidelity throughout multiple sequential single-shot weak measurements and that the partial state collapse can be reversed. Second, we use the relation between measurement st…
The antares neutrino detector instrumentation
2012
ANTARES is actually the fully operational and the largest neutrino telescope in the Northern hemisphere. Located in the Mediterranean Sea, it consists of a 3D array of 885 photomultiplier tubes (PMTs) arranged in 12 detection lines (25 storeys each), able to detect the Cherenkov light induced by upgoing relativistic muons produced in the interaction of high energy cosmic neutrinos with the detector surroundings. Among its physics goals, the search for neutrino astrophysical sources and the indirect detection of dark matter particles coming from the sun are of particular interest. To reach these goals, good accuracy in track reconstruction is mandatory, so several calibration systems for tim…
Status of the neutrino telescope AMANDA: Monopoles and WIMPs
2001
The neutrino telescope AMANDA has been set up at the geographical South Pole as first step to a neutrino telescope of the scale of one cubic kilometer, which is the canonical size for a detector sensitive to neutrinos from Active Galactic Nuclei (AGN), Gamma Ray Bursts (GRB) and Topological Defects (TD). The location and depth in which the detector is installed is given by the requirement to detect neutrinos by the Cherenkov light produced by their reaction products and to keep the background due to atmospheric muons as small as possible. However, a detector optimized for this purpose is also capable to detect the bright Cherenkov light from relativistic Monopoles and neutrino signals from …
Indirect searches for Dark Matter with the ANTARES neutrino telescope
2012
The results of a search for high-energy neutrinos coming from the direction of the Sun using the data recorded by the ANTARES neutrino telescope during 2007 and 2008 are presented. The number of neutrinos observed is found to be compatible with background expectations and upper limits for the spin-dependent and spin-independent WIMP-proton cross-sections are derived and compared to predictions of the CMSSM. These limits are comparable to those obtained by other neutrino telescopes and are more stringent than those obtained by direct search experiments for the spin-dependent WIMP-proton cross-section assuming the self-annihilation proceeds through hard channels, i.e. via W + W and t + t .
Status of the IceCube Neutrino Observatory
2004
Abstract The IceCube neutrino telescope, to be constructed near the Antarctic South Pole, represents the next generation of neutrino telescope. Its large 1 km3 size will make it uniquely sensitive to the detection of neutrinos from astrophysical sources. The current design of the detector is presented. The basic performance of the detector and its ability to search for neutrinos from various astrophysical sources has been studied using detailed simulations and is discussed.
Improving the performance of CdZnTe detectors using infrared stimulation
2011
The influence of monochromatic optical stimulation with wavelengths from 400 nm to 1100 on characteristics of the CdZnTe quasi-hemispherical detectors was studied. It was found that illumination with infrared (IR) light of wavelengths (870–900 nm) close to the absorption edge of the CdZnTe significantly improves the detectors performance at room temperature. Improvement can be achieved with low-intensity IR illumination of about 1–10 µW. The higher intensity illumination leads to degradation of the detector spectrometric characteristics. Infrared radiation penetrates into the detector sensitive volume, change the balance equilibrium between free and trapped carriers, leading to improve char…
Interaction-free evolution in the presence of time-dependent Hamiltonians
2015
The generalization of the concept of interaction-free evolutions (IFE) [A. Napoli, {\it et al.}, Phys. Rev. A {\bf 89}, 062104 (2014)] to the case of time-dependent Hamiltonians is discussed. It turns out that the time-dependent case allows for much more rich structures of interaction-free states and interaction-free subspaces. The general condition for the occurrence of IFE is found and exploited to analyze specific situations. Several examples are presented, each one associated to a class of Hamiltonians with specific features.
Measuring the mean value of vibrational observables in trapped ion systems
2002
The theoretical foundations of a new general approach to the measurement problem of vibrational observables in trapped ion systems is reported. The method rests upon the introduction of a simple vibronic coupling structure appropriately conceived to link the internal ionic state measurement outcomes to the mean value of a motional variable of interest. Some applications are provided and discussed in detail, bringing to light the feasibility and the wide potentiality of the proposal.
Geometrical characterization of non-Markovianity
2013
We introduce a new tool for the quantitative characterisation of the departure form Markovianity of a given dynamical process. Our tool can be applied to a generic $N$-level system and extended straightforwardly to Gaussian continuous-variable systems. It is linked to the change of the volume of physical states that are dynamically accessible to a system and provides qualitative expectations in agreement with some of the analogous tools proposed so far. We illustrate its prediticve power by tackling a few canonical examples.
Waveguide-QED-based measurement of a reservoir spectral density
2015
The spectral density (SD) function has a central role in the study of open quantum systems (OQSs). We discover a method allowing for a "static" measurement of the SD - i.e., it requires neither the OQS to be initially excited nor its time evolution tracked in time - which is not limited to the weak-coupling regime. This is achieved through one-dimensional photon scattering for a zero-temperature reservoir coupled to the OQS via the rotating wave approximation. We find that the SD profile is a universal simple function of the photon's reflectance and transmittance. As such, it can be straightforwardly inferred from photon's reflection and transmission spectra.