Research Articles (Physics)
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- ItemDemonstration of Shor’s factoring algorithm for N = 21 on IBM quantum processors(Nature, 2021-08-16) Skosana, Unathi; Tame, MarkWe report a proof-of-concept demonstration of a quantum order-finding algorithm for factoring the integer 21. Our demonstration involves the use of a compiled version of the quantum phase estimation routine, and builds upon a previous demonstration. We go beyond this work by using a configuration of approximate Toffoli gates with residual phase shifts, which preserves the functional correctness and allows us to achieve a complete factoring of N=21 . We implemented the algorithm on IBM quantum processors using only five qubits and successfully verified the presence of entanglement between the control and work register qubits, which is a necessary condition for the algorithm’s speedup in general. The techniques we employ may be useful in carrying out Shor’s algorithm for larger integers, or other algorithms in systems with a limited number of noisy qubits.
- ItemAtmospheric heavy metal deposition in North Macedonia from 2002 to 2010 studied by Moss biomonitoring technique(MDPI, 2020-08-30) Barandovski, Lambe; Stafilov, Trajce; Sajn, Robert; Frontasyeva, Marina; Andonovska, Katerina BacevaMoss biomonitoring technique was used for a heavy-metal pollution study in Macedonia in the framework of the International Cooperative Program on Effects of Air Pollution on Natural Vegetation and Crops (UNECE IPC Vegetation). Moss samples (n = 72) were collected during the summers of 2002, 2005, and 2010. The contents of 41 elements were determined by neutron activation analysis, atomic absorption spectrometry, and inductively coupled plasma atomic emission spectrometry. Using factor and cluster analyses, three geogenic factors were determined (Factor 1, including Al, As, Co, Cs, Fe, Hf, Na, Rb, Sc, Ta, Th, Ti, U, V, Zr, and rare-earth elements–RE; Factor 4 with Ba, K, and Sr; and Factor 5 with Br and I), one anthropogenic factor (Factor 2, including Cd, Pb, Sb, and Zn), and one geogenic-anthropogenic factor (Factor 3, including Cr and Ni). The highest anthropogenic impact of heavy metal to the air pollution in the country was from the ferronickel smelter near Kavadraci (Ni and Cr), the lead and zinc mines in the vicinity of Makedonska Kamenica, Probištip, and Kriva Palanka in the eastern part of the country (Cd, Pb, and Zn), and the former lead and zinc smelter plant in Veles. Beside the anthropogenic influences, the lithology and the composition of the soil also play an important role in the distribution of the elements.
- ItemManufacturing and characterization of in-situ alloyed Ti6Al4V(ELI)-3 at.% Cu by laser powder bed fusion(Elsevier, 2020) Vilardell, A. M.; Yadroitsev, I.; Yadroitsava, I.; Albu, M.; Takata, N.; Kobashi, M.; Krakhmalev, P.; Kouprianoff, D.; Kothleitne, G.; Du Plessis, A.Biofunctionalization of Ti6Al4V alloy with metallic agents like Ag or Cu is a promising approach to add anti-bacterial properties and thus to reduce the risk of implant failure. This research investigates the in-situ alloying of Ti6Al4V(ELI) with 3 at.% Cu powders using Laser Powder Bed Fusion (L-PBF). The morphology and geometrical characteristics of the single tracks and layers were studied. Laser powers of 170 W and 340 W, and scanning speeds ranging from 0.4 to 1.4 m/s and 0.8–2.8 m/s were implemented. Single track results showed balling effect and humping at high scanning speeds, 1.4 m/s and 1.6 m/s, for each laser powder respectively. Conversely, keyhole formation occurred at lower scanning speeds of 0.4–0.6 m/s for 170 W laser power, and below and 0.8 m/s for 340 W laser power. For both laser powers, single layers resulted in smoother surfaces at lower scanning speeds. These results were used for the development of optimal process parameters for 3D cubes with 99.9 % density. Optimal process parameters were found for 170 W and 340 W laser powders at 0.7−0.9 and 1.0–1.2 m/s scanning speeds, respectively. In-situ alloying by L-PBF was challenging and a homogeneous distribution of Cu within the alloy was hard to achieve. The increase in laser power from 170 to 340 W resulted in small increase in homogenization. Microstructural analyses after stress-relieving treatment showed the presence of α’ and β phases, as well as CuTi₂ intermetallic precipitates. The finer microstructure together with CuTi₂ intermetallic precipitates resulted in an increase in hardness. This study demonstrates the potential for printing in-situ alloyed Ti6Al4V(ELI)- 3 at.% Cu for biomedical applications. However, further studies are required to determine the effectiveness of antibacterial properties.
- ItemInvestigation on the influence of the initial RDX crystal size on the performance of shaped charge warheads(KeAi Communications, 2019) Majiet, F.; Mostert, F. J.Copper lined wave shaped shaped charges of particular design and liner metallurgy were used to investigate the effect of explosive crystal size on the resultant shaped charge jet parameters. Composition A3 with RDX of three different average crystal sizes, i.e. 30 μm, 100 μm and 300 μm were used in the investigation. All other parameters in the charge were kept constant and in particular, care was given to obtain consistent dimensional quality and liner microstructure, in order to prohibit the variation of other parameters. Specific flash-X-ray diagnostics were used in field tests to obtain the jet parameters from multiple firings of similar charges. It is found that the varying crystal size of the RDX has a marginal influence in the total jet length of the jets. However, it is also found that there is less variation between firings in the jet parameters for jets from the charges loaded with the crystal size of 100 μm.
- ItemRapid deconvolution of low-resolution time-of-flight data using Bayesian inference(AIP Publishing LLC, 2019) Pieterse, Cornelius L.; De Kock, Michiel B.; Robertson, Wesley D.; Eggers, Hans C.; Miller, R. J. DwayneThe deconvolution of low-resolution time-of-flight data has numerous advantages, including the ability to extract additional information from the experimental data. We augment the well-known Lucy-Richardson deconvolution algorithm using various Bayesian prior distributions and show that a prior of second-differences of the signal outperforms the standard Lucy-Richardson algorithm, accelerating the rate of convergence by more than a factor of four, while preserving the peak amplitude ratios of a similar fraction of the total peaks. A novel stopping criterion and boosting mechanism are implemented to ensure that these methods converge to a similar final entropy and local minima are avoided. Improvement by a factor of two in mass resolution allows more accurate quantification of the spectra. The general method is demonstrated in this paper through the deconvolution of fragmentation peaks of the 2,5-dihydroxybenzoic acid matrix and the benzyltriphenylphosphonium thermometer ion, following femtosecond ultraviolet laser desorption.