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Coherent control using adaptive learning algorithms

We have constructed an automated learning apparatus to control quantum systems. By directing intense shaped ultrafast laser pulses into a variety of samples and using a measurement of the system as a feedback signal, we are able to reshape the laser pulses to direct the system into a desired state. The feedback signal is the input to an adaptive learning algorithm. This algorithm programs a computer-controlled, acousto-optic modulator pulse shaper. The learning algorithm generates new shaped laser pulses based on the success of previous pulses in achieving a predetermined goal.Comment: 19 pages (including 14 figures), REVTeX 3.1, updated conten

Constructive control of quantum systems using factorization of unitary operators

We demonstrate how structured decompositions of unitary operators can be employed to derive control schemes for finite-level quantum systems that require only sequences of simple control pulses such as square wave pulses with finite rise and decay times or Gaussian wavepackets. To illustrate the technique it is applied to find control schemes to achieve population transfers for pure-state systems, complete inversions of the ensemble populations for mixed-state systems, create arbitrary superposition states and optimize the ensemble average of dynamic observables.Comment: 28 pages, IoP LaTeX, principal author has moved to Cambridge University ([email protected]

Inelastic light, neutron, and X-ray scatterings related to the heterogeneous elasticity of glasses

The effects of plasticization of poly(methyl methacrylate) glass on the boson peaks observed by Raman and neutron scattering are compared. In plasticized glass the cohesion heterogeneities are responsible for the neutron boson peak and partially for the Raman one, which is enhanced by the composition heterogeneities. Because the composition heterogeneities have a size similar to that of the cohesion ones and form quasiperiodic clusters, as observed by small angle X-ray scattering, it is inferred that the cohesion heterogeneities in a normal glass form nearly periodic arrangements too. Such structure at the nanometric scale explains the linear dispersion of the vibrational frequency versus the transfer momentum observed by inelastic X-ray scattering.Comment: 9 pages, 2 figures, to be published in J. Non-Cryst. Solids (Proceedings of the 4th IDMRCS

Anharmonicity, vibrational instability and Boson peak in glasses

We show that a {\em vibrational instability} of the spectrum of weakly interacting quasi-local harmonic modes creates the maximum in the inelastic scattering intensity in glasses, the Boson peak. The instability, limited by anharmonicity, causes a complete reconstruction of the vibrational density of states (DOS) below some frequency $\omega_c$, proportional to the strength of interaction. The DOS of the new {\em harmonic modes} is independent of the actual value of the anharmonicity. It is a universal function of frequency depending on a single parameter -- the Boson peak frequency, $\omega_b$ which is a function of interaction strength. The excess of the DOS over the Debye value is $\propto\omega^4$ at low frequencies and linear in $\omega$ in the interval $\omega_b \ll \omega \ll \omega_c$. Our results are in an excellent agreement with recent experimental studies.Comment: LaTeX, 8 pages, 6 figure

Electronic structure of nuclear-spin-polarization-induced quantum dots

We study a system in which electrons in a two-dimensional electron gas are confined by a nonhomogeneous nuclear spin polarization. The system consists of a heterostructure that has non-zero nuclei spins. We show that in this system electrons can be confined into a dot region through a local nuclear spin polarization. The nuclear-spin-polarization-induced quantum dot has interesting properties indicating that electron energy levels are time-dependent because of the nuclear spin relaxation and diffusion processes. Electron confining potential is a solution of diffusion equation with relaxation. Experimental investigations of the time-dependence of electron energy levels will result in more information about nuclear spin interactions in solids

Origin of the v. portae and variability of its tributaries in laboratory animals. V. The golden (Syrian) hamster (Mesocricetus auratus).

The authors studied the origin and variability of the v. portae in 30 adult golden hamsters (Mesocricetus auratus) of both sexes after injecting blue-dyed latex into their portal bed. In 16 cases (53.3%) the v. portae was formed from three tributaries and in 11 cases (36.7%) from four. The v. mesenterica cranialis was the only constant tributary, the v. lienalis was a tributary in 28 cases (93.3%) and the other most frequent tributaries were the v. gastroduodenalis and the v. pancreaticoduodenalis cranialis. In one case there was an anastomosis between the v. portae and the v. cava caudalis. In 25 cases (83.3%) the v. gastrica sinistra joined the v. lienalis, in four (13.3%) it was an independent tributary of the v. portae and in one case (3.3%) it was duplicated. A v. cardiaca was found in 25 cases (83.3%), when it was most frequently a tributary of the v. gastroepiploica sinistra and v. gastrica sinistra. In one case only it was an independent tributary of the v. portae. A v. pylorica was observed in 29 cases (96.7%), usually (in 17 cases--56.7%) as a tributary of the v. gastroepiploica dextra; in three cases it was an independent tributary of the v. portae (10.0%). A v. pancreaticoduodenalis cranialis was formed in 28 cases (93.3%). In 12 cases (40.0%), together with the v. gastroepiploica dextra, it was a tributary of the v. gastroduodenalis and in eight cases (26.7%) it was an independent tributary of the v. portae. In two cases (6.7%) the two vv. pancreaticoduodenales united to form v. pancreaticoduodenalis communis. In three cases (10.0%) this vein was duplicated and in one case it was triplicated. A v. gastroepiploica dextra was found in 26 cases (86.7%) and a v. gastroepiploica sinistra in 22 (73.3%). Both veins occurred simultaneously in 19 cases (63.3%). In no case, however, was there a continuous venous arc along the curvatura major ventriculi. A v. lienalis was present in 28 cases (93.3%). It was absent in two cases (6.7%), in which it was replaced by inter-organ anastomoses with the stomach and pancreas. In 19 cases (63.3%), the v. gastroepiploica sinistra and v. gastrica sinistra were both its main tributaries and in five cases (16.7%) its main tributary was the v. gastrica sinistra. In one case the v. lienalis was duplicated. Inter-organ anastomoses were formed in all 30 cases (100%). They occurred between the spleen and the stomach in 27 cases (90%) and between the spleen and the pancreas in 28 cases (93.3%).(ABSTRACT TRUNCATED AT 400 WORDS

Variability of the v. cava caudalis and its tributaries in some laboratory animals. II. The laboratory rat (Rattus norvegicus v. alba).

Duplication of the v. renalis was found in 11 of the regions examined (18.3%), when it was more frequent on the right side. A v. capsularis was found in 35 regions (58.3%), usually as a single vein. There were 1-3 vv. suprarenales (but mostly two; on the right they usually joined the v. cava caudalis and on the left the v. renalis sinistra). A v. spermatica was present on the right side in every case, but on the left side in 11 cases only; in one case it was duplicated. In the rat, the v. spermatica was rather thin; if absent, it was replaced by the v. deferentialis. In nine cases (60.0%) the v. uterina cranialis dextra opened into the v. cava caudalis, while in 12 cases (80.0%) the left vein opened into the v. renalis sinistra. A v. uterina media, draining blood from the caudal third of the cornu uteri, was found in only five cases (16.7%). The v. uterina caudalis drained blood from the corpus and cervix uteri. The v. ovarica was a constant finding; it was mostly joined by the v. lumbalis--and on the left side by the v. phrenica sinistra. In males, the vv. lumbales occurred mostly as a pair of veins lying just below the vv. renales. In females, they were present on both sides. As a rule, the v. iliolumbalis occurred as a single vein on both sides. The v. cava caudalis originated at the level of the transition between the lumbar and the sacral spine, usually at the confluence of the two vv. iliacae communes, which in 14 cases (46.7%) were joined by the v. sacralis mediana. Duplication of the v. cava caudalis was found in only one case (a female). Comparison of the morphology of the v. cava caudalis and its tributaries in the rat and the guinea pig showed more slight differences between the two species