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Implementing quantum logic operations, pseudo-pure states and the Deutsch-Jozsa algorithm using non-commuting selective pulses in NMR  [PDF]
Kavita Dorai,Arvind,Anil Kumar
Physics , 1999, DOI: 10.1103/PhysRevA.61.042306
Abstract: We demonstrate experimentally the usefulness of selective pulses in NMR to perform quantum computation. Three different techniques based on selective pulse excitations have been proposed to prepare a spin system in a pseudo-pure state. We describe the design of novel ``portmanteau'' gates using the selective manipulation of level populations. A selective pulse implementation of the Deutsch-Jozsa algorithm for a two-qubit and a three-qubit quantum computer is demonstrated.
Subsystem Pseudo-pure States  [PDF]
P. Cappellaro,J. S. Hodges,T. F. Havel,D. G. Cory
Physics , 2006, DOI: 10.1103/PhysRevA.75.042321
Abstract: A critical step in experimental quantum information processing (QIP) is to implement control of quantum systems protected against decoherence via informational encodings, such as quantum error correcting codes, noiseless subsystems and decoherence free subspaces. These encodings lead to the promise of fault tolerant QIP, but they come at the expense of resource overheads. Part of the challenge in studying control over multiple logical qubits, is that QIP test-beds have not had sufficient resources to analyze encodings beyond the simplest ones. The most relevant resources are the number of available qubits and the cost to initialize and control them. Here we demonstrate an encoding of logical information that permits the control over multiple logical qubits without full initialization, an issue that is particularly challenging in liquid state NMR. The method of subsystem pseudo-pure state will allow the study of decoherence control schemes on up to 6 logical qubits using liquid state NMR implementations.
Coherence Transfer in Spatially Resolved NMR
Narayanan Chandrakumar
Magnetic Resonance Insights , 2012,
Abstract: We present an overview of some applications of coherence transfer experiments in spatially resolved NMR, with examples from imaging and volume localized spectroscopy. While the major preoccupation of spatially resolved NMR experiments is normally with the dominant component (e.g. water) of heterogeneous multi-component systems, the interest in minor components (e.g. metabolites) of such systems is a strong motivation to develop and apply special techniques. Unlike water, these components typically involve scalar coupled spin systems. They lend themselves therefore to investigations based on the correlated evolution of coupled spins. Specifically, we briefly describe in this contribution the spatially resolved version of multiple quantum experiments, indirect detection experiments and spin correlation experiments.
Coherence Transfer in Spatially Resolved NMR
Narayanan Chandrakumar
Magnetic Resonance Insights , 2008,
Abstract: We present an overview of some applications of coherence transfer experiments in spatially resolved NMR, with examples from imaging and volume localized spectroscopy. While the major preoccupation of spatially resolved NMR experiments is normally with the dominant component (e.g. water) of heterogeneous multi-component systems, the interest in minor components (e.g. metabolites) of such systems is a strong motivation to develop and apply special techniques. Unlike water, these components typically involve scalar coupled spin systems. They lend themselves therefore to investigations based on the correlated evolution of coupled spins. Specifically, we briefly describe in this contribution the spatially resolved version of multiple quantum experiments, indirect detection experiments and spin correlation experiments.
Preparation of pseudo-pure states by line-selective pulses in Nuclear Magnetic Resonance  [PDF]
Xinhua Peng,Xiwen Zhu,Ximing Fang,Mang Feng,Keli Gao,Xiaodong Yang,Maili Liu
Physics , 2000, DOI: 10.1016/S0009-2614(01)00421-3
Abstract: A new method of preparing the pseudo-pure state of a spin system for quantum computation in liquid nuclear magnetic resonance (NMR) was put forward and demonstrated experimentally. Applying appropriately connected line-selective pulses simultaneously and a field gradient pulse techniques we acquired straightforwardly all pseudo-pure states for two qubits in a single experiment much efficiently. The signal intensity with the pseudo-pure state prepared in this way is the same as that of temporal averaging. Our method is suitable for the system with arbitrary numbers of qubits. As an example of application, a highly structured search algorithm----Hogg's algorithm was also performed on the pseudo-pure state $\mid 00>$ prepared by our method.
Magnetic properties of pure and Gd doped EuO probed by NMR  [PDF]
Arnaud Comment,Jean-Philippe Ansermet,Charles P. Slichter,Heesuk Rho,Clark S. Snow,S. Lance Cooper
Physics , 2004, DOI: 10.1103/PhysRevB.72.014428
Abstract: An Eu NMR study in the ferromagnetic phase of pure and Gd doped EuO was performed. A complete description of the NMR lineshape of pure EuO allowed for the influence of doping EuO with Gd impurities to be highlighted. The presence of a temperature dependent static magnetic inhomogeneity in Gd doped EuO was demonstrated by studying the temperature dependence of the lineshapes. The results suggest that the inhomogeneity in 0.6% Gd doped EuO is linked to colossal magnetoresistance. The measurement of the spin-lattice relaxation times as a function of temperature led to the determination of the value of the exchange integral J as a function of Gd doping. It was found that J is temperature independent and spatially homogeneous for all the samples and that its value increases abruptly with increasing Gd doping.
Relaxation of Pseudo pure states : The Role of Cross-Correlations  [PDF]
Arindam Ghosh,Anil Kumar
Physics , 2005, DOI: 10.1016/j.jmr.2004.11.013
Abstract: In Quantum Information Processing by NMR one of the major challenges is relaxation or decoherence. Often it is found that the equilibrium mixed state of a spin system is not suitable as an initial state for computation and a definite initial state is required to be prepared prior to the computation. As these preferred initial states are non-equilibrium states, they are not stationary and are destroyed with time as the spin system relaxes toward its equilibrium, introducing error in computation. Since it is not possible to cut off the relaxation processes completely, attempts are going on to develop alternate strategies like Quantum Error Correction Codes or Noiseless Subsystems. Here we study the relaxation behavior of various Pseudo Pure States and analyze the role of Cross terms between different relaxation processes, known as Cross-correlation. It is found that while cross-correlations accelerate the relaxation of certain pseudo pure states, they retard that of others.
Fractional topological phase on spatially encoded photonic qudits  [PDF]
A. Z. Khoury,L. E. Oxman,B. Marques,A. Matoso,S. Pádua
Physics , 2013, DOI: 10.1103/PhysRevA.87.042113
Abstract: We discuss the appearance of fractional topological phases on cyclic evolutions of entangled qudits encoded on photonic degrees of freedom. We show how the spatial correlations between photons generated by spontaneous parametric down conversion can be used to evidence the multiple topological phases acquired by entangled qudits and the role played by the Hilbert space dimension. A realistic experimental proposal is presented with numerical predictions of the expected results.
Pure subrings of regular rings are pseudo-rational  [PDF]
Hans Schoutens
Mathematics , 2005,
Abstract: We prove a generalization of the Hochster-Roberts-Boutot-Kawamata Theorem conjectured by Aschenbrenner and the author: let $R\to S$ be a pure homomorphism of equicharacteristic zero Noetherian local rings. If $S$ is regular, then $R$ is pseudo-rational, and if $R$ is moreover $\mathbb Q$-Gorenstein, then it pseudo-log-terminal.
Spatio-temporal characterization of mid-infrared laser pulses with spatially encoded spectral shearing interferometry  [PDF]
Tobias Witting,Sebastien J. Weber,John W. G. Tisch,Jonathan P. Marangos
Physics , 2012, DOI: 10.1364/OE.20.027974
Abstract: We report on the spatially resolved full amplitude and phase characterization of mid-infrared high intensity laser pulses generated in a three stage OPA. We use a spatially-encoded arrangement (SEA-)SPIDER with spectral filters for ancilla generation for spatially resolved characterization. Using five interchangeable filter sets we are able to characterize pulses from 1 to 2{\mu}m with one single device with minimal adjustments.
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