Precision of single-qubit gates based on Raman transitions

We analyze the achievable precision for single-qubit gates that are based on Raman transitions between two near-degenerate ground states via a virtually excited state. In particular, we study the errors due to non-perfect adiabaticity and due to spontaneous emission from the excited state. For the case of non-adabaticity, we calculate the error as a function of the dimensionless parameter $\chi=\Delta \tau$, where $\Delta$ is the detuning of the Raman beams and $\tau$ is the gate time. For the case of spontaneous emission, we give an analytical argument that the gate errors are approximately equal to $\Lambda \gamma/\Delta$, where $\Lambda$ is the rotation angle of the one-qubit gate and $\gamma$ is the spontaneous decay rate, and we show numerically that this estimate holds to good approximation.Comment: 8 pages, 10 figure

Adsorption and reactions of CH2I2 on Ru(001) surface

Denna rapport behandlar en energianalys av fastigheten Björnen i Mariestad. I rapportenkommer aspekter som antags vara kritiska för byggnadens energianvändning att behandlas.Exempel presenteras på hur framtagande av dokumentation och behandling av existerandesådan gjordes. Att dokumentation saknas eller inte är uppdaterad kan innebära problem dåfastigheten skall analyseras. Detta problem eftersträvas delvis att elimineras i denna rapportgenom de analyser som görs.Ett syfte med rapporten är att ta fram möjliga förtjänster som framtida energieffektiviseringsåtgärder påverkar. Exempelvis vid en renovering. Emellertid är en heltäckande förståelse förhur den i fastighetens tillförda fjärrvärmeenergi tillförs och används i byggnaden central. Enkartläggning av hur fastigheten fungerar i nuläget med till exempel energisignatur, samt samladstatistik finns också att tillgå. Detta skall fungera som ett underlag inför eventuella framtidaenergieffektiviserande åtgärder i fastigheten.This report is covering an energy analysis of the property Björnen, Mariestad. The report willcover aspects assumed to have a critical impact on the energy use of this property in particular.Examples on how produce documentation and analysis of existing documentation is covered.Missing documentation or badly organized one can cause major problems in an energy analysis.This problem is sought to be partially eliminated through this report.One purpose of this report is to declare possible profits that may be the result of proposed energyefficiency actions regarding this property. Actions such as renovation. The central purpose,however, is to create an understanding of how this property in particular is using the energydelivered to it. A survey of how the property is functioning in these aspects with appurtenantstatistics and analysis are covered. This should act as a base of thought to consider for possibleactions taken with this property in the future

Carbon nanotubes adhesion and nanomechanical behavior from peeling force spectroscopy

Applications based on Single Walled Carbon Nanotube (SWNT) are good example of the great need to continuously develop metrology methods in the field of nanotechnology. Contact and interface properties are key parameters that determine the efficiency of SWNT functionalized nanomaterials and nanodevices. In this work we have taken advantage of a good control of the SWNT growth processes at an atomic force microscope (AFM) tip apex and the use of a low noise (1E-13 m/rtHz) AFM to investigate the mechanical behavior of a SWNT touching a surface. By simultaneously recording static and dynamic properties of SWNT, we show that the contact corresponds to a peeling geometry, and extract quantities such as adhesion energy per unit length, curvature and bending rigidity of the nanotube. A complete picture of the local shape of the SWNT and its mechanical behavior is provided

On a generalization of the binomial distribution and its Poisson-like limit

We examine a generalization of the binomial distribution associated with a strictly increasing sequence of numbers and we prove its Poisson-like limit. Such generalizations might be found in quantum optics with imperfect detection. We discuss under which conditions this distribution can have a probabilistic interpretation.Comment: 17 pages, 6 figure

Probing the inter-layer exciton physics in a MoS2_2/MoSe2_2/MoS2_2 van der Waals heterostructure

Stacking atomic monolayers of semiconducting transition metal dichalcogenides (TMDs) has emerged as an effective way to engineer their properties. In principle, the staggered band alignment of TMD heterostructures should result in the formation of inter-layer excitons with long lifetimes and robust valley polarization. However, these features have been observed simultaneously only in MoSe$_2$/WSe$_2$ heterostructures. Here we report on the observation of long lived inter-layer exciton emission in a MoS$_2$/MoSe$_2$/MoS$_2$ trilayer van der Waals heterostructure. The inter-layer nature of the observed transition is confirmed by photoluminescence spectroscopy, as well as by analyzing the temporal, excitation power and temperature dependence of the inter-layer emission peak. The observed complex photoluminescence dynamics suggests the presence of quasi-degenerate momentum-direct and momentum-indirect bandgaps. We show that circularly polarized optical pumping results in long lived valley polarization of inter-layer exciton. Intriguingly, the inter-layer exciton photoluminescence has helicity opposite to the excitation. Our results show that through a careful choice of the TMDs forming the van der Waals heterostructure it is possible to control the circular polarization of the inter-layer exciton emission.Comment: 19 pages, 3 figures. Just accepted for publication in Nano Letters (http://pubs.acs.org/doi/10.1021/acs.nanolett.7b03184