Secure Positioning of Mobile Terminals with Simplex Radio Communication

With the rapid spread of various mobile terminals in our society, the importance of secure positioning is growing for wireless networks in adversarial settings. Recently, several authors have proposed a secure positioning mechanism of mobile terminals which is based on the geometric property of wireless node placement, and on the postulate of modern physics that a propagation speed of information never exceeds the velocity of light. In particular, they utilize the measurements of the round-trip time of radio signal propagation and bidirectional communication for variants of the challenge-and-response. In this paper, we propose a novel means to construct the above mechanism by use of unidirectional communication instead of bidirectional communication. Our proposal is based on the assumption that a mobile terminal incorporates a high-precision inner clock in a tamper-resistant protected area. In positioning, the mobile terminal uses its inner clock and the time and location information broadcasted by radio from trusted stations. Our proposal has a major advantage in protecting the location privacy of mobile terminal users, because the mobile terminal need not provide any information to the trusted stations through positioning procedures. Besides, our proposal is free from the positioning error due to claimant\u27s processing-time fluctuations in the challenge-and-response, and is well-suited for mobile terminals in the open air, or on the move at high speed, in terms of practical usage. We analyze the security, the functionality, and the feasibility of our proposal in comparison to previous proposals

Exact Solutions of Holonomic Quantum Computation

Holonomic quantum computation is analyzed from geometrical viewpoint. We develop an optimization scheme in which an arbitrary unitary gate is implemented with a small circle in a complex projective space. Exact solutions for the Hadamard, CNOT and 2-qubit discrete Fourier transform gates are explicitly constructed.Comment: 11 pages, re-organized to be more comprehensive, references added, style file of Physics Letters A is neede

Quantum receiver beyond the standard quantum limit of coherent optical communication

The most efficient modern optical communication is known as coherent communication and its standard quantum limit (SQL) is almost reachable with current technology. Though it has been predicted for a long time that this SQL could be overcome via quantum mechanically optimized receivers, such a performance has not been experimentally realized so far. Here we demonstrate the first unconditional evidence surpassing the SQL of coherent optical communication. We implement a quantum receiver with a simple linear optics configuration and achieve more than 90% of the total detection efficiency of the system. Such an efficient quantum receiver will provide a new way of extending the distance of amplification-free channels, as well as of realizing quantum information protocols based on coherent states and the loophole-free test of quantum mechanics.Comment: 5 pages, 3 figure

Realization of Arbitrary Gates in Holonomic Quantum Computation

Among the many proposals for the realization of a quantum computer, holonomic quantum computation (HQC) is distinguished from the rest in that it is geometrical in nature and thus expected to be robust against decoherence. Here we analyze the realization of various quantum gates by solving the inverse problem: Given a unitary matrix, we develop a formalism by which we find loops in the parameter space generating this matrix as a holonomy. We demonstrate for the first time that such a one-qubit gate as the Hadamard gate and such two-qubit gates as the CNOT gate, the SWAP gate and the discrete Fourier transformation can be obtained with a single loop.Comment: 8 pages, 6 figure

Immuno-chemotherapy of malignant lymphoma using OK-432, a streptococcal agent

Clinical trials of immuno-chemotherapy were conducted on malignant lymphoma patients. Patients during the period from 1972 through 1977 were allocated to two groups retrospectively according to the mode of treatment, i.e., chemotherapy alone (historical control group, 35 patients) and chemotherapy with OK-432 (treated group, 15 patients). Comparisons were made of the two groups, which were homogeneous with regard to induction chemotherapy, maintenance chemotherapy, stage and histologic type of disease. The treated group had a higher remission rate, and a longer remission duration and survival than the control groups, especially in patients with Hodgkin's disease but the difference was not statistically significant owing to the limited number of cases.</p

Continuous-Variable Quantum Teleportation with a Conventional Laser

We give a description of balanced homodyne detection (BHD) using a conventional laser as a local oscillator (LO), where the laser field outside the cavity is a mixed state whose phase is completely unknown. Our description is based on the standard interpretation of the quantum theory for measurement, and accords with the experimental result in the squeezed state generation scheme. We apply our description of BHD to continuous-variable quantum teleportation (CVQT) with a conventional laser to analyze the CVQT experiment [A. Furusawa et al., Science 282, 706 (1998)], whose validity has been questioned on the ground of intrinsic phase indeterminacy of the laser field [T. Rudolph and B.C. Sanders, Phys. Rev. Lett. 87, 077903 (2001)]. We show that CVQT with a laser is valid only if the unknown phase of the laser field is shared among sender's LOs, the EPR state, and receiver's LO. The CVQT experiment is considered valid with the aid of an optical path other than the EPR channel and a classical channel, directly linking between a sender and a receiver. We also propose a method to probabilistically generate a strongly phase-correlated quantum state via continuous measurement of independent lasers, which is applicable to realizing CVQT without the additional optical path.Comment: 5 pages, 2 figure

Fractional Absorption of Active Absorbable Algal Calcium (AAACa) and Calcium Carbonate Measured by a Dual Stable-Isotope Method

With the use of stable isotopes, this study aimed to compare the bioavailability of active absorbable algal calcium (AAACa), obtained from oyster shell powder heated to a high temperature, with an additional heated seaweed component (Heated Algal Ingredient, HAI), with that of calcium carbonate. In 10 postmenopausal women volunteers aged 59 to 77 years (mean ± S.D., 67 ± 5.3), the fractional calcium absorption of AAACa and CaCO3 was measured by a dual stable isotope method. 44Ca-enriched CaCO3 and AAACa were administered in all subjects one month apart. After a fixed-menu breakfast and pre-test urine collection (Urine 0), 42Ca-enriched CaCl2 was intravenously injected, followed by oral administration of 44Ca-enriched CaCO3 without carrier 15 minutes later, and complete urine collection for the next 24 hours (Urine 24). The fractional calcium absorption was calculated as the ratio of Augmentation of 44Ca from Urine 0 to Urine 24/ augmentation of 42Ca from Urine 0 to Urine 24. Differences and changes of 44Ca and 42Ca were corrected by comparing each with 43Ca. Fractional absorption of AAACa (mean ± S.D., 23.1 ± 6.4), was distinctly and significantly higher than that of CaCO3 (14.7 ± 6.4; p = 0.0060 by paired t-test). The mean fractional absorption was approximately 1.57-times higher for AAACa than for CaCO3. The serum 25(OH) vitamin D level was low (mean ± S.D., 14.2 ± 4.95 ng/ml), as is common in this age group in Japan. Among the parameters of the bone and mineral metabolism measured, none displayed a significant correlation with the fractional absorption of CaCO3 and AAACa. Higher fractional absorption of AAACa compared with CaCO3 supports previous reports on the more beneficial effect of AAACa than CaCO3 for osteoporosis