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We describe portable software to simulate universal quantum computers on massive parallel computers. We illustrate the use of the simulation software by running various quantum algorithms on different computer architectures, such as a IBM BlueGene/L, a IBM Regatta p690+, a Hitachi SR11000/J1, a Cray X1E, a SGI Altix 3700 and clusters of PCs running Windows XP. We study the performance of the software by simulating quantum computers containing up to 36 qubits, using up to 4096 processors and up to 1 TB of memory. Our results demonstrate that the simulator exhibits nearly ideal scaling as a function of the number of processors and suggest that the simulation software described in this paper may also serve as benchmark for testing high-end parallel computers.

We present a detailed numerical study of the electronic properties of single-layer graphene with resonant ("hydrogen") impurities and vacancies within a framework of noninteracting tight-binding model on a honeycomb lattice. The algorithms are based on the numerical solution of the timedependent Schrödinger equation and applied to calculate the density of states, quasieigenstates, AC and DC conductivities of large samples containing millions of atoms. Our results give a consistent picture of evolution of electronic structure and transport properties of functionalized graphene in a broad range of concentration of impurities (from graphene to graphane), and show that the formation of impurity band is the main factor determining electrical and optical properties at intermediate impurity concentrations, together with a gap opening when approaching the graphane limit.

We study the properties of Suzuki's systematic approximations to the exponential operator exp( -PH) by calculating the thermodynamic functions of three simple quantum models. We demonstrate that the path-integral representation of the partition function obtained from these approximations can be simplified and made more accurate by constructing Hermitian versions of Suzuki's expressions.

A corpuscular simulation model of optical phenomena that does not require the knowledge of the solution of a wave equation of the whole system and reproduces the results of Maxwell's theory by generating detection events one-by-one is presented. The event-based corpuscular model is shown to give a unified description of multiple-beam fringes of a plane parallel plate, singlephoton Mach-Zehnder interferometer, Wheeler's delayed choice, photon tunneling, quantum erasers, two-beam interference, double-slit, and Einstein-Podolsky-Rosen-Bohm and Hanbury Brown-Twiss experiments.

We demonstrate that networks of locally connected processing units with a primitive learning capability exhibit behavior that is usually only attributed to quantum systems. We describe networks that simulate single-photon beam-splitter and Mach-Zehnder interferometer experiments on a causal, event-by-event basis and demonstrate that the simulation results are in excellent agreement with quantum theory.( * )

It is shown that the basic equations of quantum theory can be obtained from a straightforward application of logical inference to experiments for which there is uncertainty about individual events and for which the frequencies of the observed events are robust with respect to small changes in the conditions under which the experiments are carried out.Keywords: logical inference, quantum theory, inductive logic, probability theory 10 from classical (or quantum) mechanics is lacking and therefore the answer should be "no" but in practice this does not matter too much. Our belief in thermodynamics is not based on mathematical deduction but on its power to account for everyday experience.It has been emphasized many times that our description of physical phenomena at some level of observation is essentially independent of our view of "underlying" levels [2]. In the present paper, we apply the 15 same world view to nonrelativistic quantum theory. Adopting this view immediately distinguishes our line of thinking from approaches that assume an underlying ontology [3, 4,5,6, 7] or formulate quantum theory Email addresses: h.a.de.raedt@rug.nl (Hans De Raedt), M.Katsnelson@science.ru.nl (Mikhail I. Katsnelson), 1. There is no quantum world. There is only an abstract physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature [45]. 302. Physics is to be regarded not so much as the study of something a priori given, but rather as the development of methods of ordering and surveying human experience. In this respect our task must be to account for such experience in a manner independent of individual subjective judgment and therefore objective in the sense that it can be unambiguously communicated in ordinary human language [46]. 3. The physical content of quantum mechanics is exhausted by its power to formulate statistical laws 35 governing observations under conditions specified in plain language [46].The first two sentences of the first quote may be read as a suggestion to dispose of, in Mermin's words [47], the "bad habit" to take mathematical abstractions as the reality of the events (in the everyday sense of the word) that we experience through our senses. Although widely circulated, these sentences are reported by Petersen [45] and there is doubt that Bohr actually used this wording [48]. The last two sentences of the first 40 quote and the second quote suggest that we should try to describe human experiences (confined to the realm of scientific inquiry) in a manner and language which is unambiguous and independent of the individual subjective judgment. Of course, the latter should not be construed to imply that the observed phenomena are independent of the choices made by the individual(s) in performing the scientific experiment [49].The third quote suggests that quantum theory is a powerful language to describe a certain class of 45 statistical experiments but remains vague about the properties of the class. Similar views were expres...