Quantifying multiparticle entanglement with randomized measurements

Randomized measurements constitute a simple measurement primitive that exploits the information encoded in the outcome statistics of samples of local quantum measurements defined through randomly selected bases. In this work we exploit the potential of randomized measurements in order to probe the amount of entanglement contained in multiparticle quantum systems as quantified by the multiparticle concurrence. We further present a detailed statistical analysis of the underlying measurement resources required for a confident estimation of the introduced quantifiers using analytical tools from the theory of random matrices. The introduced framework is demonstrated by a series of numerical experiments analyzing the concurrence of typical multiparticle entangled states as well as of ensembles of output states produced by random quantum circuits. Finally, we examine the multiparticle entanglement of mixed states produced by noisy quantum circuits consisting of single- and two-qubit gates with non-vanishing depolarization errors, thus showing that our framework is directly applicable in the noisy intermediate-scale regime.Comment: 17 pages, 8 figure

Determination of the bandgap and split-off band of wurtzite GaAs

GaAs nanowires with a 100% wurtzite structure are synthesized by the vapor-liquid-solid method in a molecular beam epitaxy system, using gold as a catalyst. We use resonant Raman spectroscopy and photoluminescence to determine the position of the crystal-field split-off band of hexagonal wurtzite GaAs. The temperature dependence of this transition enables us to extract the value at 0 K, which is 1.982 eV. Our photoluminescence excitation spectroscopy measurements are consistent with a band gap of GaAs wurtzite below 1.523 eV

Complete characterization of quantum correlations by randomized measurements

The fact that quantum mechanics predicts stronger correlations than classical physics is an essential cornerstone of quantum information processing. Indeed, these quantum correlations are a valuable resource for various tasks, such as quantum key distribution or quantum teleportation, but characterizing these correlations in an experimental setting is a formidable task, especially in scenarios where no shared reference frames are available. By definition, quantum correlations are reference-frame independent, i.e., invariant under local transformations; this physically motivated invariance implies, however, a dedicated mathematical structure and, therefore, constitutes a roadblock for an efficient analysis of these correlations in experiments. Here we provide a method to directly measure any locally invariant property of quantum states using locally randomized measurements, and we present a detailed toolbox to analyze these correlations for two quantum bits. We implement these methods experimentally using pairs of entangled photons, characterizing their usefulness for quantum teleportation and their potential to display quantum nonlocality in its simplest form. Our results can be applied to various quantum computing platforms, allowing simple analysis of correlations between arbitrary distant qubits in the architecture.Comment: 5 pages + 15 pages of appendix, 4 figure

Repeated injections of 131I-rituximab show patient-specific stable biodistribution and tissue kinetics

Purpose: It is generally assumed that the biodistribution and pharmacokinetics of radiolabelled antibodies remain similar between dosimetric and therapeutic injections in radioimmunotherapy. However, circulation half-lives of unlabelled rituximab have been reported to increase progressively after the weekly injections of standard therapy doses. The aim of this study was to evaluate the evolution of the pharmacokinetics of repeated 131I-rituximab injections during treatment with unlabelled rituximab in patients with non-Hodgkin's lymphoma (NHL). Methods: Patients received standard weekly therapy with rituximab (375mg/m2) for 4 weeks and a fifth injection at 7 or 8 weeks. Each patient had three additional injections of 185MBq 131I-rituximab in either treatment weeks 1, 3 and 7 (two patients) or weeks 2, 4 and 8 (two patients). The 12 radiolabelled antibody injections were followed by three whole-body (WB) scintigraphic studies during 1 week and blood sampling on the same occasions. Additional WB scans were performed after 2 and 4 weeks post 131I-rituximab injection prior to the second and third injections, respectively. Results: A single exponential radioactivity decrease for WB, liver, spleen, kidneys and heart was observed. Biodistribution and half-lives were patient specific, and without significant change after the second or third injection compared with the first one. Blood T1/2β, calculated from the sequential blood samples and fitted to a bi-exponential curve, was similar to the T1/2 of heart and liver but shorter than that of WB and kidneys. Effective radiation dose calculated from attenuation-corrected WB scans and blood using Mirdose3.1 was 0.53+0.05mSv/MBq (range 0.48-0.59mSv/MBq). Radiation dose was highest for spleen and kidneys, followed by heart and liver. Conclusion: These results show that the biodistribution and tissue kinetics of 131I-rituximab, while specific to each patient, remained constant during unlabelled antibody therapy. RIT radiation doses can therefore be reliably extrapolated from a preceding dosimetry stud