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Quantum Computation (quantum + computation)

Distribution by Scientific Domains

Physics and Astronomy	50%
Chemistry	50%

Selected Abstracts

Proceedings of the 2nd International Conference on Semiconductor Quantum Dots (QD2002)

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2003
Y. Arakawa
The International Conference on Semiconductor Quantum Dots (QD2002) was held at Komaba Campus of University of Tokyo, Japan, from Monday, 30 September, through Thursday, 3 October 2002. The purpose of the QD2002 was to bring together scientists from different fields of physics and chemistry to discuss topics of common interest and significance in such growing areas including semiconductor quantum dots, nanocrystals, and clusters. The conference was focused on the optical and electronic properties of three-dimensionally confined nanostructures grown both by epitaxial methods and chemical preparation routes. The QD2002 was the second in a series which started in Munich, Germany, in 2000. The scope of the QD2002 covered various research fields including novel fabrication techniques of nanoheterostructures, electronic structures, optical properties, electronic properties/single electron tunneling processes, molecular dots, nanocrystals, device applications such as lasers and memories, coherent processes/quantum computations, and biomedical applications. [source]

One-way quantum computation via manipulation of polarization and momentum qubits in two-photon cluster states

LASER PHYSICS LETTERS, Issue 5 2008
G. Vallone
Abstract Four-qubit cluster states of two photons entangled in polarization and linear momentum have been used to realize a complete set of single qubit rotations and the C-NOT gate for equatorial qubits with high values of fidelity. By the computational equivalence of the two degrees of freedom our result demonstrate the suitability of two photon cluster states for rapid and efficient one-way quantum computing. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Generation and interrogation of a pure nuclear spin state by parahydrogen-enhanced NMR spectroscopy: a defined initial state for quantum computation

MAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2005
D. Blazina
Abstract We describe a number of studies used to establish that parahydrogen can be used to prepare a two-spin system in a pure state, which is suitable for implementing NMR quantum computation. States are generated by pulsed and continuous-wave (CW) UV laser initiation of a chemical reaction between Ru(CO)3(L2) [where L2 = dppe = 1,2-bis(diphenylphosphino)ethane or L2 = dpae = 1,2-bis(diphenylarsino)ethane] with pure parahydrogen (generated at 18 K). This process forms Ru(CO)2(dppe)(H)2 and Ru(CO)2(dpae)(H)2 on a sub-microsecond time-scale. With the pulsed laser, the spin state of the hydride nuclei in Ru(CO)2(dppe)(H)2 has a purity of 89.8 ± 2.6% (from 12 measurements). To achieve comparable results by cooling would require a temperature of 6.6 mK, which is unmanageable in the liquid state, or an impractical magnetic field of 0.44 MT at room temperature. In the case of CW initiation, reduced state purities are observed due to natural signal relaxation even when a spin-lock is used to prevent dephasing. When Ru(CO)3(dpae) and pulsed laser excitation are utilized, the corresponding dihydride product spin state purity was determined as 106 ± 4% of the theoretical maximum. In other words, the state prepared using Ru(CO)3(dpae) as the precursor is indistinguishable from a pure state. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Initialization and logic gate operations of nuclear spin qubits using a submicron scale resistively-detected NMR device

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008
T. Ota
Abstract We demonstrate initialization of nuclear spin qubits using a resistively-detected nuclear magnetic resonance (NMR) device. In our device, nuclear spins are dynamically polarized in a sub-micron scale region defined by split gates. The population of each nuclear spin state is estimated from a resistively-detected NMR spectrum combined with numerical analysis. By applying radio frequency pulses to the polarized nuclear spins, we create two-qubit effective pure states, which is a crucial step toward NMR quantum computation. We also demonstrate simple logic gate operations such as controlled-NOT and SWAP gates in this two-qubit system. The obtained spectra are consistent with numerically calculated ones. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Models of S/, interactions in protein structures: Comparison of the H2S,benzene complex with PDB data

PROTEIN SCIENCE, Issue 10 2007
Ashley L. Ringer
Abstract S/, interactions are prevalent in biochemistry and play an important role in protein folding and stabilization. Geometries of cysteine/aromatic interactions found in crystal structures from the Brookhaven Protein Data Bank (PDB) are analyzed and compared with the equilibrium configurations predicted by high-level quantum mechanical results for the H2S,benzene complex. A correlation is observed between the energetically favorable configurations on the quantum mechanical potential energy surface of the H2S,benzene model and the cysteine/aromatic configurations most frequently found in crystal structures of the PDB. In contrast to some previous PDB analyses, configurations with the sulfur over the aromatic ring are found to be the most important. Our results suggest that accurate quantum computations on models of noncovalent interactions may be helpful in understanding the structures of proteins and other complex systems. [source]