Modification of Non-Metallic Inclusions by Rare-Earth Elements in Microalloyed Steels

The modification of the chemical composition of non-metallic inclusions by rare-earth elements in the new-developed microalloyed steels was discussed in the paper. The investigated steels are assigned to production of forged elements by thermo- mechanical treatment. The steels were melted in a vaccum induction furnace and modification of non-metallic inclusions was carried out by the michmetal in the amount of 2.0 g per 1 kg of steel. It was found that using material charge of high purity and a realization of metallurgical process in vacuous conditions result in a low concentration of sulfur (0.004%), phosphorus (from 0.006 to 0.008%) and oxygen (6 ppm). The high metallurgical purity is confirmed by a small fraction of non-metallic inclusions averaging 0.075%. A large majority of non-metallic inclusions are fine, globular oxide-sulfide or sulfide particles with a mean size 17m2. The chemical composition and morphology of non-metallic inclusions was modified by Ce, La and Nd, what results a small deformability of non- metallic inclusions during hot-working

Switchable resonant coupling of flux qubits

We propose a coupling scheme, where two or more flux qubits with different eigenfrequencies share Josephson junctions with a coupler loop devoid of its own quantum dynamics. Switchable two-qubit coupling is realized by tuning the frequency of the AC magnetic flux through the coupler to a combination frequency of two of the qubits. The coupling allows any or all of the qubits to be simultaneously at the degeneracy point and can change sign.Comment: REVTeX 4, 4 pages, 2 figures, v2: reference added, v3: final version published in Phys. Rev.

Supercurrent-phase relationship of a Nb/InAs(2DES)/Nb Josephson junction in overlapping geometry

Superconductor/normal conductor/superconductor (SNS) Josephson junctions with highly transparent interfaces are predicted to show significant deviations from sinusoidal supercurrent-phase relationships (CPR) at low temperatures. We investigate experimentally the CPR of a ballistic Nb/InAs(2DES)/Nb junction in the temperature range from 1.3 K to 9 K using a modified Rifkin-Deaver method. The CPR is obtained from the inductance of the phase-biased junction. Transport measurements complement the investigation. At low temperatures, substantial deviations of the CPR from conventional tunnel-junction behavior have been observed. A theoretical model yielding good agreement to the data is presented.Comment: RevTex4, 4 pages including 3 figure

How to test the "quantumness" of a quantum computer?

We discuss whether, to what extent and how a quantum computing device can be evaluated and simulated using classical tools.Comment: Submitted 12.10.201

Superconducting gap parameters of MgB2 obtained on MgB2/Ag and MgB2/In junctions

MgB2 superconducting wires with critical temperature Tc approaching 40 K were used for preparation of MgB2/Ag and MgB2/In junctions. The differential conductance vs. voltage characteristics of N-S junctions exhibit clear contribution of Andreev reflection. Using modified BTK theory for s-wave superconductors two order parameters 4 meV and 2.6 meV have been determined from temperature dependencies. Surprisingly, larger order parameter vanishes at lower temperature ~20 K than smaller one with Tc 38 K. Both the magnitudes of the order parameters and their critical temperatures are in good agreement with theoretical calculations of electron-phonon coupling in MgB$_2$ carried out by Liu et al.Comment: revised manuscrip