Search results for "FOS"
showing 10 items of 15075 documents
Haptotropism in a Nickel Complex with a Neutral, π‐Bridging cyclo‐P4 Ligand Analogous to Cyclobutadiene
2022
The reaction of ( 1 )Ni(η 2 -cod), 2 , incorporating a chelating bis( N -heterocyclic carbene) 1 , with P 4 in pentane yielded the dinuclear complex [( 2 )Ni] 2 (μ 2 ,η 2 :η 2 -P 4 ), 3 , formally featuring a cyclobutadiene-like, neutral, rectangular, π-bridging P 4 -ring. In toluene, the butterfly-shaped complex [( 1 )Ni] 2 (μ 2 ,η 2 :η 2 -P 2 ), 4 , with a formally neutral P 2 -unit was obtained from 2 and either P 4 or 3 . Computational studies showed that a low energy barrier haptotropic rearrangement involving two isomers of the μ 2 ,η 2 :η 2 -P 4 coordination mode and a low energy μ 2 ,η 4 :η 4 -P 4 coordination mode, as previously predicted for related nickel cyclobutadiene complexes…
Noiseless Quantum Measurement and Squeezing of Microwave Fields Utilizing Mechanical Vibrations
2017
A process which strongly amplifies both quadrature amplitudes of an oscillatory signal necessarily adds noise. Alternatively, if the information in one quadrature is lost in phase-sensitive amplification, it is possible to completely reconstruct the other quadrature. Here we demonstrate such a nearly perfect phase-sensitive measurement using a cavity optomechanical scheme, characterized by an extremely small noise less than 0.2 quanta. We also observe microwave radiation strongly squeezed by 8 dB below vacuum. A source of bright squeezed microwaves opens up applications in manipulations of quantum systems, and noiseless amplification can be used even at modest cryogenic temperatures.
Inference of proto-neutron star properties from gravitational-wave data in core-collapse supernovae
2021
The eventual detection of gravitational waves from core-collapse supernovae (CCSN) will help improve our current understanding of the explosion mechanism of massive stars. The stochastic nature of the late post-bounce gravitational wave signal due to the non-linear dynamics of the matter involved and the large number of degrees of freedom of the phenomenon make the source parameter inference problem very challenging. In this paper we take a step towards that goal and present a parameter estimation approach which is based on the gravitational waves associated with oscillations of proto-neutron stars (PNS). Numerical simulations of CCSN have shown that buoyancy-driven g-modes are responsible …
Johnson-Nyquist Noise Effects in Neutron Electric-Dipole-Moment Experiments
2021
Magnetic Johnson-Nyquist noise (JNN) originating from metal electrodes, used to create a static electric field in neutron electric-dipole-moment (nEDM) experiments, may limit the sensitivity of measurements. We present here the first dedicated study on JNN applied to a large-scale long-measurement-time experiment with the implementation of a co-magnetometry. In this study, we derive surface- and volume-averaged root-mean-square normal noise amplitudes at a certain frequency bandwidth for a cylindrical geometry. In addition, we model the source of noise as a finite number of current dipoles and demonstrate a method to simulate temporal and three-dimensional spatial dependencies of JNN. The c…
Experimental on-demand recovery of entanglement by local operations within non-Markovian dynamics
2015
In many applications entanglement must be distributed through noisy communication channels that unavoidably degrade it. Entanglement cannot be generated by local operations and classical communication (LOCC), implying that once it has been distributed it is not possible to recreate it by LOCC. Recovery of entanglement by purely local control is however not forbidden in the presence of non-Markovian dynamics, and here we demonstrate in two all-optical experiments that such entanglement restoration can even be achieved on-demand. First, we implement an open-loop control scheme based on a purely local operation, without acquiring any information on the environment; then, we use a closed-loop s…
Quantum Non-Markovian Piecewise Dynamics from Collision Models
2017
Recently, a large class of quantum non-Markovian piecewise dynamics for an open quantum system obeying closed evolution equations has been introduced [B. Vacchini, Phys. Rev. Lett. 117, 230401 (2016)]. These dynamics have been defined in terms of a waiting-time distribution between quantum jumps, along with quantum maps describing the effect of jumps and the system's evolution between them. Here, we present a quantum collision model with memory, whose reduced dynamics in the continuous-time limit reproduces the above class of non-Markovian piecewise dynamics, thus providing an explicit microscopic realization.
Recovering a variable exponent
2021
We consider an inverse problem of recovering the non-linearity in the one dimensional variable exponent $p(x)$-Laplace equation from the Dirichlet-to-Neumann map. The variable exponent can be recovered up to the natural obstruction of rearrangements. The main technique is using the properties of a moment problem after reducing the inverse problem to determining a function from its $L^p$-norms.
Very narrow quantum OBDDs and width hierarchies for classical OBDDs
2014
In the paper we investigate a model for computing of Boolean functions - Ordered Binary Decision Diagrams (OBDDs), which is a restricted version of Branching Programs. We present several results on the comparative complexity for several variants of OBDD models. - We present some results on the comparative complexity of classical and quantum OBDDs. We consider a partial function depending on a parameter k such that for any k > 0 this function is computed by an exact quantum OBDD of width 2, but any classical OBDD (deterministic or stable bounded-error probabilistic) needs width 2 k+1. - We consider quantum and classical nondeterminism. We show that quantum nondeterminism can be more efficien…
On the CAT(0) dimension of 2-dimensional Bestvina-Brady groups
2002
Let K be a 2-dimensional finite flag complex. We study the CAT(0) dimension of the `Bestvina-Brady group', or `Artin kernel', Gamma_K. We show that Gamma_K has CAT(0) dimension 3 unless K admits a piecewise Euclidean metric of non-positive curvature. We give an example to show that this implication cannot be reversed. Different choices of K lead to examples where the CAT(0) dimension is 3, and either (i) the geometric dimension is 2, or (ii) the cohomological dimension is 2 and the geometric dimension is not known.
Mass measurements of As, Se, and Br nuclei, and their implication on the proton-neutron interaction strength toward the N=Z line
2021
Mass measurements of the $^{69}$As, $^{70,71}$Se and $^{71}$Br isotopes, produced via fragmentation of a $^{124}$Xe primary beam at the FRS at GSI, have been performed with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS Ion Catcher with an unprecedented mass resolving power of almost 1,000,000. For the $^{69}$As isotope, this is the first direct mass measurement. A mass uncertainty of 22 keV was achieved with only 10 events. For the $^{70}$Se isotope, a mass uncertainty of 2.6 keV was obtained, corresponding to a relative accuracy of $\delta$m/m = 4.0$\times 10^{-8}$, with less than 500 events. The masses of the $^{71}$Se and $^{71}$Br isotopes were measured…