Exact solution of the Schrodinger equation with the spin-boson Hamiltonian

We address the problem of obtaining the exact reduced dynamics of the spin-half (qubit) immersed within the bosonic bath (enviroment). An exact solution of the Schrodinger equation with the paradigmatic spin-boson Hamiltonian is obtained. We believe that this result is a major step ahead and may ultimately contribute to the complete resolution of the problem in question. We also construct the constant of motion for the spin-boson system. In contrast to the standard techniques available within the framework of the open quantum systems theory, our analysis is based on the theory of block operator matrices.Comment: 9 pages, LaTeX, to appear in Journal of Physics A: Mathematical and Theoretica

Defects in Quantum Computers

The shift of interest from general purpose quantum computers to adiabatic quantum computing or quantum annealing calls for a broadly applicable and easy to implement test to assess how quantum or adiabatic is a specific hardware. Here we propose such a test based on an exactly solvable many body system -- the quantum Ising chain in transverse field -- and implement it on the D-Wave machine. An ideal adiabatic quench of the quantum Ising chain should lead to an ordered broken symmetry ground state with all spins aligned in the same direction. An actual quench can be imperfect due to decoherence, noise, flaws in the implemented Hamiltonian, or simply too fast to be adiabatic. Imperfections result in topological defects: Spins change orientation, kinks punctuating ordered sections of the chain. The number of such defects quantifies the extent by which the quantum computer misses the ground state, and is, therefore, imperfect.Comment: 8 pages, 7 figures, to appear in Scientific Reports, authors' list complete

Quantum neural networks to simulate many-body quantum systems

We conduct experimental simulations of many body quantum systems using a \emph{hybrid} classical-quantum algorithm. In our setup, the wave function of the transverse field quantum Ising model is represented by a restricted Boltzmann machine. This neural network is then trained using variational Monte Carlo assisted by a D-Wave quantum sampler to find the ground state energy. Our results clearly demonstrate that already the first generation of quantum computers can be harnessed to tackle non-trivial problems concerning physics of many body quantum systems.Comment: 6 pages, 4 figure

PVT Property Measurements for Ethyl Propionate, Ethyl Butyrate, and Ethyl Pentanoate Esters from (298 to 393) K and up to 35 MPa

The results of PVT measurements of the liquid phase within the temperature range (298 to 393) K and up to 35 MPa are presented for some aliphatic esters. Measurements were made by means of a vibrating tube densimeter, model DMA 512P from Anton Parr. The calibration of the densimeter was performed with water and n-heptane as reference fluids. The experimental PVT data have been correlated by a Tait equation. This equation gives good results when used to predict the density of the esters using the method proposed by Thomson et al. Isothermal compressibilities, isobaric expansivities, thermal pressure coefficients, and changes in the isobaric heat capacity have been calculated from the Tait equation

19 Radioterapia ziarnicy złośliwej u dzieci w materiale I Zakładu Teleradioterapii Centrum

W latach 1986–1998 w I Zakładzie Radioterapii Centrum Onkologii w Warszawie leczono 97 dzieci z rozpoznaniem ziarnicy złośliwej, w wieku od 2 do 18 lat. Ponad połowa pacjentów (58%) była powyżej 10 roku życia. Obserwowano znaczną przewagę chłopców M.:F = 1,77. Przeważali pacjenci w I i w II stopniu zaawansowania klinicznego (63%) i bez objawów ogólnych (62%). W rozpoznaniu histopatologicznym najczęstsza była postać NS (50%) i MC (31%).Wszystkie dzieci otrzymały leczenie chemiczne przed napromienianiem. U 71 zastosowano program B-POPA, u 18 COPP/OPPA, u pozostałych 9 inne schematy leczenia. Pacjenci byli napromieniani na teren pierwotnie zajętych okolic węzłowych, promieniami telekobaltu-60. Stosowano dawki od 20 do 36 Gy, przeważnie 25 Gy (u 65%).Obecnie żyje 91 pacjentów, zmarło jedno dziecko, 5 stracono z obserwacji. Osiemdziesięciu pacjentówzyje żyje bez nawrotu choroby. U żadnego z pozostających w obserwacji dzieci nie stwierdzono póżnych powikłań po napromienianiu