Non-perturbative Interband Response of InSb Driven Off-resonantly by Few-cycle Electromagnetic Transients

Intense multi-THz pulses are used to study the coherent nonlinear response of bulk InSb by means of field-resolved four-wave mixing spectroscopy. At amplitudes above 5 MV/cm the signals show a clear temporal substructure which is unexpected in perturbative nonlinear optics. Simulations based on a two-level quantum system demonstrate that in spite of the strongly off-resonant character of the excitation the high-field pulses drive the interband resonances into a non-perturbative regime of Rabi flopping.Comment: 4 pages, 4 figure

Pressure-induced insulator-to-metal transition in low-dimensional TiOCl

We studied the transmittance and reflectance of the low-dimensional Mott-Hubbard insulator TiOCl in the infrared and visible frequency range as a function of pressure. The strong suppression of the transmittance and the abrupt increase of the near-infrared reflectance above 12 GPa suggest a pressure-induced insulator-to-metal transition. The pressure-dependent frequency shifts of the orbital excitations, as well as the pressure dependences of the charge gap and the spectral weight of the optical conductivity above the phase transition are presented.Comment: 4 pages, 6 figure

Immunohistochemical Markers in the Assessment of Tumor Response

The examination of the possibility of using immunohistochemical and molecular (NCRT) and prognostic factors of the disease state. The study included 21 patients with locally advanced gastric cancer. All patients underwent the NCRT followed by gastrectomy D2. We analyzed the expression of HER2 / neu marker, Ki-67, p53, Cyklin D1, E-cadherin in biopsy (before therapy) and the operating material (after chemoradiotherapy and the treatment gap). We have found statistically significant decrease in the expression of Ki-67 markers and Cyklin D1, a trend towards to a decrease of p53 expression after the NCRT. The dynamics of expression of immunohistochemical markers examination is a promising approach in search for predictors of NCRT effectiveness for patients with locally advanced gastric cancer. Keywords: neoadjuvant chemoradiotherapy, immunohistochemical markers, molecular genetic markers, therapeutic pathomorphism, gastric cancer

Effect of high pressure on multiferroic BiFeO3

We report experimental evidence for pressure instabilities in the model multiferroic BiFeO3 and namely reveal two structural phase transitions around 3 GPa and 10 GPa by using diffraction and far-infrared spectroscopy at a synchrotron source. The intermediate phase from 3 to 9 GPa crystallizes in a monoclinic space group, with octahedra tilts and small cation displacements. When the pressure is further increased the cation displacements (and thus the polar character) of BiFeO3 is suppressed above 10 GPa. The above 10 GPa observed non-polar orthorhombic Pnma structure is in agreement with recent theoretical ab-initio prediction, while the intermediate monoclinic phase was not predicted theoretically.Comment: new version, accepted for publication in Phys. Rev.

Parallel pumping of electrons

We present simultaneous operation of ten single-electron turnstiles leading to one order of magnitude increase in current level up to 100 pA. Our analysis of device uniformity and background charge stability implies that the parallelization can be made without compromising the strict requirements of accuracy and current level set by quantum metrology. In addition, we discuss how offset charge instability limits the integration scale of single-electron turnstiles.Comment: 6 pages, 4 figures, 1 tabl

Auxiliary-level-assisted operations with charge qubits in semiconductors

We present a new scheme for rotations of a charge qubit associated with a singly ionized pair of donor atoms in a semiconductor host. The logical states of such a qubit proposed recently by Hollenberg et al. are defined by the lowest two energy states of the remaining valence electron localized around one or another donor. We show that an electron located initially at one donor site can be transferred to another donor site via an auxiliary molecular level formed upon the hybridization of the excited states of two donors. The electron transfer is driven by a single resonant microwave pulse in the case that the energies of the lowest donor states coincide or two resonant pulses in the case that they differ from each other. Depending on the pulse parameters, various one-qubit operations, including the phase gate, the NOT gate, and the Hadamard gate, can be realized in short times. Decoherence of an electron due to the interaction with acoustic phonons is analyzed and shown to be weak enough for coherent qubit manipulation being possible, at least in the proof-of-principle experiments on one-qubit devices.Comment: Extended version of cond-mat/0411605 with detailed discussion of phonon-induced decoherence including dephasing and relaxation; to be published in JET

Coherent quantum phase slip

A hundred years after discovery of superconductivity, one fundamental prediction of the theory, the coherent quantum phase slip (CQPS), has not been observed. CQPS is a phenomenon exactly dual to the Josephson effect: whilst the latter is a coherent transfer of charges between superconducting contacts, the former is a coherent transfer of vortices or fluxes across a superconducting wire. In contrast to previously reported observations of incoherent phase slip, the CQPS has been only a subject of theoretical study. Its experimental demonstration is made difficult by quasiparticle dissipation due to gapless excitations in nanowires or in vortex cores. This difficulty might be overcome by using certain strongly disordered superconductors in the vicinity of the superconductor-insulator transition (SIT). Here we report the first direct observation of the CQPS in a strongly disordered indium-oxide (InOx) superconducting wire inserted in a loop, which is manifested by the superposition of the quantum states with different number of fluxes. Similarly to the Josephson effect, our observation is expected to lead to novel applications in superconducting electronics and quantum metrology.Comment: 14 pages, 3 figure

Dispersive Manipulation of Paired Superconducting Qubits

We combine the ideas of qubit encoding and dispersive dynamics to enable robust and easy quantum information processing (QIP) on paired superconducting charge boxes sharing a common bias lead. We establish a decoherence free subspace on these and introduce universal gates by dispersive interaction with a LC resonator and inductive couplings between the encoded qubits. These gates preserve the code space and only require the established local symmetry and the control of the voltage bias.Comment: 5 pages, incl. 1 figur

Superconductor-ferromagnet junction phase qubit

We propose a scheme for a phase qubit in an SIFIS junction, consisting of bulk superconductors (S), a proximity-induced ferromagnet (F), and insulating barriers (I). The qubit state is constituted by 0 and $\pi$ phase states of the junction, in which the charging energy of the junction leads to the superposition of the two states. The qubit is operated by the gate voltage applied to the ferromagnet, and insensitive to the decoherence sources existing in other superconducting qubits. We discuss a scalable scheme for qubit measurement and tunable two-qubit coupling.Comment: 3 pages, 3 figure