Tight bound on coherent-state-based entanglement generation over lossy channels

The first stage of the hybrid quantum repeaters is entanglement generation based on transmission of pulses in coherent states over a lossy channel. Protocols to make entanglement with only one type of error are favorable for rendering subsequent entanglement distillation efficient. Here we provide the tight upper bound on performances of these protocols that is determined only by the channel loss. In addition, we show that this bound is achievable by utilizing a proposed protocol [arXiv:0811.3100] composed of a simple combination of linear optical elements and photon-number-resolving detectors.Comment: 12 pages, 3 figure

Quantum repeaters and computation by a single module

We present a protocol of remote nondestructive parity measurement (RNPM) on a pair of quantum memories. The protocol works as a single module for key operations such as entanglement generation, Bell measurement, parity check measurement, and an elementary gate for extending one-dimensional cluster states. The RNPM protocol is achieved by a simple combination of devices such as lasers, optical fibers, beam splitters, and photon detectors. Despite its simplicity, a quantum repeater composed of RNPM protocols is shown to have a communication time that scales sub-exponentially with the channel length, and it can be further equipped with entanglement distillation. With a reduction in the internal losses, the RNPM protocol can also be used for generating cluster states toward measurement-based quantum communication.Comment: 7 pages, 4 figure

Probabilistic cloning with supplementary information

We consider probabilistic cloning of a state chosen from a mutually nonorthogonal set of pure states, with the help of a party holding supplementary information in the form of pure states. When the number of states is 2, we show that the best efficiency of producing m copies is always achieved by a two-step protocol in which the helping party first attempts to produce m-1 copies from the supplementary state, and if it fails, then the original state is used to produce m copies. On the other hand, when the number of states exceeds two, the best efficiency is not always achieved by such a protocol. We give examples in which the best efficiency is not achieved even if we allow any amount of one-way classical communication from the helping party.Comment: 6 pages, no figure

Optimal supplier of single-error-type entanglement via coherent-state transmission

Compared with entanglement with multiple types of noise, entanglement including only one type of error is a favorable fundamental resource not only for quantum communication but also for distributed quantum computation. We consider protocol that presents single-error-type entanglement for distant qubits via coherent-state transmission over a lossy channel. This protocol is regarded as a subroutine to serve entanglement for larger protocol to yield a final output, such as ebits or pbits. In this paper, we provide a subroutine protocol which achieves the global optimal for typical jointly convex yield functions monotonically non-decreasing with respect to the singlet fraction, such as an arbitrary convex function of a singlet fraction and two-way distillable entanglement/key. Entanglement generation based on remote non-destructive parity measurement protocol [K. Azuma, H. Takeda, M. Koashi, and N. Imoto, Phys. Rev. A 85, 062309 (2012)] is identified as such an optimal subroutine.Comment: 12 pages, 6 figure

COPD・肺がんの予防

Chronic obstructive pulmonary disease (COPD) is a long-standing, crippling disease characterized by the accelerated decline of lung function, commonly brought by aging and long-time inhalation of toxic chemicals such as tobacco smoking. Consequently, most COPD patients suffer from chronic cough, sputum and dyspnea on exertion. Moreover, in addition to the decline of lung function due to the destruction of the alveolar structure, COPD is closely related to other diseases such as osteoporosis, cardiovascular diseases, diabetes, muscle dysfuncion, and lung cancer. Therefore, COPD is currently recognized as a systemic disease that the comprehensive management and care are necessary. Although COPD represents an increasing burden throughout the world and is one of the major causes of death word-wide, the issue has been arisen that the recognition of COPD in the general society is still low, especially in Japan. On the other hand, lung cancer is a life-threatening disease with the leading cause of malignancy-related death world-wide, the etiology of which is also closely related to tobacco smoking. Because the pathogenesis and the mortality of COPD and lung cancer are closely related each other, the action to prevent these diseases could be made simultaneously, primarily by the smoking cessation and the detection survey. In this article, we describe the present situation of COPD and lung cancer, the importance of smoking cessation, and the effort of Tokushima City Medical Association to manage COPD in Tokushima

Cholecystitis caused by a fish bone.

The accidental ingestion of a foreign body is not uncommon. However, the presence of a foreign body in the gallbladder is extremely rare. Here, we present a case of cholecystitis due to a fish bone that may have penetrated through the stomach wall and into the gallbladder without causing peritonitis. A laparoscopic cholecystectomy was performed; a fish bone, measuring 4.0 cm in length, was found in the gallbladder. To the best of our knowledge, this is the first such case to be reported

An Experimental Evaluation of Tracheal Blood Flow with Special Referrence to Operative Procedure of Tracheal Mobilization

Based on the study with special referrence to blood flow in the trachea, the factors influential on the operative procedure of tracheal mobilization were carefully evaluated to ensure optimal surgical results. It has already been assumed with an aid of microangiographic technique that the main trancheal blood flow comprise two routes, namely, adventitial and submucosal layers. The amount of blood flow in the trachea divided into individual two layers were measured by hydrogen clearance test with wire electrodes placed in either adventitial or submucosal layer. When employed the procedure of extensive mobilization of the trachea, the level of tracheal blood flow reduced in adventitial layer rather lthan in submucosal layer. Blood flow in submucosal layer, however, remain closely near the normal level, which is thought to compensate a decreased blood supply in the tracheal adventitia. Meanwhile, when proposed an excessive tension of more than 800g at the site of anastomosis, a decrease in submucosal blood flow has become manifest despite of a slight decrease in adventitial blood flow simultaneously. Greater emphasis has been focused upo