Influence of qubit displacements on quantum logic operations in a silicon-based quantum computer with constant interaction

The errors caused by qubit displacements from their prescribed locations in an ensemble of spin chains are estimated analytically and calculated numerically for a quantum computer based on phosphorus donors in silicon. We show that it is possible to polarize (initialize) the nuclear spins even with displaced qubits by using Controlled NOT gates between the electron and nuclear spins of the same phosphorus atom. However, a Controlled NOT gate between the displaced electron spins is implemented with large error because of the exponential dependence of exchange interaction constant on the distance between the qubits. If quantum computation is implemented on an ensemble of many spin chains, the errors can be small if the number of chains with displaced qubits is small

Single-Spin Microscope with Sub-Nanoscale Resolution Based on Optically Detected Magnetic Resonance

We summarize our new scanning magnetic 3-D imaging system. This scanning system uses optically detected magnetic resonance in a single nitrogen vacancy center in a diamond nanocrystal. The theoretical analysis and the first experimental demonstrations have proved that this method has single spin sensitivity and a sub-nanoscale spatial resolution at room temperature.Comment: 4 pages, 2 figure

Resonant Perturbation Theory of Decoherence and Relaxation of Quantum Bits

We describe our recent results on the resonant perturbation theory of decoherence and relaxation for quantum system with many qubits. The approach represents a rigorous analysis of the phenomenon of decoherence and relaxation for general $N$-level systems coupled to reservoirs of the bosonic fields. We derive a representation of the reduced dynamics valid for all times $t\geq 0$ and for small but fixed interaction strength. Our approach does not involve master equation approximations and applies to a wide variety of systems which are not explicitly solvable

Natural Entropy Production in an Inflationary Model for a Polarized Vacuum

Though entropy production is forbidden in standard FRW Cosmology, Berman and Som presented a simple inflationary model where entropy production by bulk viscosity, during standard inflation without ad hoc pressure terms can be accommodated with Robertson-Walker's metric, so the requirement that the early Universe be anisotropic is not essential in order to have entropy growth during inflationary phase, as we show. Entropy also grows due to shear viscosity, for the anisotropic case. The intrinsically inflationary metric that we propose can be thought of as defining a polarized vacuum, and leads directly to the desired effects without the need of introducing extra pressure terms.Comment: 7 pages including front one. Accepted to publication, Astrophysics and Space Science, subjected to a minor correction, already submitte

International NGOs in New York City: A Comparative Study

New York City is a global city, not just for its place in the global market, or for its role as an innovator of policy. This report indicates it should also be known for its significant contributions in the field of international nongovernmental organizations (INGOs). Using data collected from IRS Form 990 tax filings, this report creates the first comprehensive assessment of the INGO sector in NYC and demonstrates that New York City's INGO sector is not only a leader of the nationwide INGO sector, but it also reflects the city's unique history and diverse population

Dynamical Stability and Quantum Chaos of Ions in a Linear Trap

The realization of a paradigm chaotic system, namely the harmonically driven oscillator, in the quantum domain using cold trapped ions driven by lasers is theoretically investigated. The simplest characteristics of regular and chaotic dynamics are calculated. The possibilities of experimental realization are discussed.Comment: 24 pages, 17 figures, submitted to Phys. Rev

Growth on the border or bordering on growth ?

Economic development ; Economic conditions - Texas