D. F. V. James

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We demonstrate complete characterization of a two-qubit entangling process--a linear optics controlled-NOT gate operating with coincident detection--by quantum process tomography. We use a maximum-likelihood estimation to convert the experimental data into a physical process matrix. The process matrix allows an accurate prediction of the operation of the(More)
Evidence of cell-mediated immunity to gastric intrinsic factor was present in 86% of patients with pernicious anaemia and in at least 13% of patients with hyperthyroidism, 21% of patients with atrophic gastritis, and four out of nine (46%) patients with hypogammaglobulinaemia. Controls gave negative results. The four patients with hypogammaglobulinaemia and(More)
Autoimmunity to platelets was looked for by complement fixation, antiglobulin consumption, transformation and migration-inhibition techniques. Only the migration-inhibition method gave consistently positive results. The test was positive in nine out of 14 patients with idiopathic thrombocytopenic purpura and all five patients with glandular fever.
Shor's powerful quantum algorithm for factoring represents a major challenge in quantum computation. Here, we implement a compiled version in a photonic system. For the first time, we demonstrate the core processes, coherent control, and resultant entangled states required in a full-scale implementation. These are necessary steps on the path towards(More)
We describe a scalable, high-speed, and robust architecture for measurement-based quantum computing with trapped ions. Measurement-based architectures offer a way to speed up operation of a quantum computer significantly by parallelizing the slow entangling operations and transferring the speed requirement to fast measurement of qubits. We show that a 3D(More)
The ability to detect very weak optical fields with high efficiency (>99%) and to distinguish the number of photons in a given time interval is a very challenging technical problem with enormous potential payoffs in quantum communications and information processing. We propose to employ an atomic vapor as the active medium, prepared in a specific quantum(More)
Much like its classical counterpart, which aims at reconstructing threedimensional images via a series of two-dimensional projections along various ‘cuts’, quantum tomography characterizes the complete quantum state of a particle or particles through a series of measurements in different bases. While the characterization of a classical object can involve a(More)
A. G. White,* D. F. V. James, W. J. Munro, and P. G. Kwiat Department of Physics, University of Queensland, Brisbane, Queensland 4072, Australia Theory Division, T-4 and Physics Division, P-23, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 Maths, Cryptography and Security Group, Hewlett-Packard Laboratories, Bristol BS34 8QZ, United Kingdom(More)