On the optimality of individual entangling-probe attacks against BB84 quantum key distribution

It is shown that an existing method to study ideal individual attacks on the BB84 QKD protocol using error discard can be adapted to reconciliation with error correction, and that an optimal attack can be explicitly found. Moreover, this attack fills Luetkenhaus bound, independently of whether error positions are leaked to Eve, proving that it is tight. In addition, we clarify why the existence of such optimal attacks is not in contradiction with the established ``old-style'' theory of BB84 individual attacks, as incorrectly suggested recently in a news feature.Comment: 12 pages, 3 figure

Biocompatibility of materials and products used in medicine and dental medicine

BackgroundBiomaterials are defined as substances intended to replace a part of the body or its function in a secure, safe and economical way, while being physiologically and aesthetically acceptable. Biomaterials can be bioinert or regenerative. Biocompatibility refers to the ability of a material to elicit a specific biological response after administration in a living organism. Measuring the biocompatibility of materials used in dentistry is not an easily achievable task.MethodsScientific databases – PubMed, Scopus and Medline, as well as monographs, textbooks on the topic, websites were used to search for the data required. The following keywords were used: biomaterials, biocompatibility, dental medicine, medicine, toxicity.The aim of the following article is to summarize the main conclusions authors in the field have reached to when discussing biocompatibility and tolerance of material and products used in medicine and dental medicine.Results and discussionIn depth results and discussion are presented in the section. Materials used in medicine and dental medicine encompass a wide range of compounds, with different chemical and physical structures. Therefore, profound knowledge is needed to be able to treat the patients and keep them safe as much as possible from possible adverse biological reactions.ConclusionsMedical and dental specialists should pay special attention to the content of the materials they implement in their treatment plans on a daily basis. Being profoundly informed on the general diseases, medications usage and allergic status of their patients can prevent adverse complications. Although medicine explores and studies in depth possible biological reactions, still they may occur

Attacks on quantum key distribution protocols that employ non-ITS authentication

We demonstrate how adversaries with unbounded computing resources can break Quantum Key Distribution (QKD) protocols which employ a particular message authentication code suggested previously. This authentication code, featuring low key consumption, is not Information-Theoretically Secure (ITS) since for each message the eavesdropper has intercepted she is able to send a different message from a set of messages that she can calculate by finding collisions of a cryptographic hash function. However, when this authentication code was introduced it was shown to prevent straightforward Man-In-The-Middle (MITM) attacks against QKD protocols. In this paper, we prove that the set of messages that collide with any given message under this authentication code contains with high probability a message that has small Hamming distance to any other given message. Based on this fact we present extended MITM attacks against different versions of BB84 QKD protocols using the addressed authentication code; for three protocols we describe every single action taken by the adversary. For all protocols the adversary can obtain complete knowledge of the key, and for most protocols her success probability in doing so approaches unity. Since the attacks work against all authentication methods which allow to calculate colliding messages, the underlying building blocks of the presented attacks expose the potential pitfalls arising as a consequence of non-ITS authentication in QKD-postprocessing. We propose countermeasures, increasing the eavesdroppers demand for computational power, and also prove necessary and sufficient conditions for upgrading the discussed authentication code to the ITS level.Comment: 34 page

Vanishing Integral Relations and Expectation Values for Bloch Functions in Finite Domains

Integral identities for particular Bloch functions in finite periodic systems are derived. All following statements are proven for a finite domain consisting of an integer number of unit cells. It is shown that matrix elements of particular Bloch functions with respect to periodic differential operators vanish identically. The real valuedness, the time-independence and a summation property of the expectation values of periodic differential operators applied to superpositions of specific Bloch functions are derived.Comment: 10 page

A Novel Protocol-Authentication Algorithm Ruling Out a Man-in-the-Middle Attack in Quantum Cryptography

In this work we review the security vulnerability of Quantum Cryptography with respect to "man-in-the-middle attacks" and the standard authentication methods applied to counteract these attacks. We further propose a modified authentication algorithm which features higher efficiency with respect to consumption of mutual secret bits.Comment: 4 pages, submitted to the International Journal of Quantum Information, Proceedings of the meeting "Foundations of Quantum Information", Camerino, April 200

Vestibular effects of diving

Over the last 45 years, recreational self-contained underwater breathing apparatus (SCUBA) diving as a leisure activity has increased in popularity. According to the Professional Association of Diving Instructors (PADI), more than 23 million diver certificates have been issued across the globe. Given the popularity of scuba diving, it is incumbent on every physician to know and understand the specific medical hazards and conditions associated with scuba diving. Although diving has become more accessible and the equipment is much safer now, diving still has its inherent dangers. Each year incidents occur, ranging from seasickness and sinus problems to heart conditions and mortality. More than 80% of all diving complications occur in the head and neck region. A number of studies have found that diving can lead to the development of vestibular disorders such as: Barotrauma, Decompression sickness, Otitis externa, Bilateral exostoses, Chronic sinusitis (barosinusitis), Serous tubotympanic catarrh, Tinnitus, Dizziness, Vertigo.The aim of this paper was to share our experience in the field of treating patients with different types of ENT disorders after or before a diving session. We briefly summarized the most important information for some of the disorders.We included in our study for a period of 12 years: a total of 24 patients (four females and 20 males), who dive. They were between 25 and 55 years of age. Some presented in clinics with an ENT disorder. 19 were professional, qualified divers, five (three males and two females) dove for the first time. On all 24 patients we performed: audiometry tests, Tympanometry tests, OAE, Static and dynamic vestibular tests, vHIT – in the last five years, otoscopy examination, dental check-ups.All divers – no matter professionalists or not – should follow these recommendations: a thorough prophylactic ENT check-up should be performed before an active diving session. Chronic ENT inflammations should be addressed in a timely manner. Divers should follow all instructions from the certified Diving Associations

New intensity and visibility aspects of a double loop neutron interferometer

Various phase shifters and absorbers can be put into the arms of a double loop neutron interferometer. The mean intensity levels of the forward and diffracted beams behind an empty four plate interferometer of this type have been calculated. It is shown that the intensities in the forward and diffracted direction can be made equal using certain absorbers. In this case the interferometer can be regarded as a 50/50 beam splitter. Furthermore the visibilities of single and double loop interferometers are compared to each other by varying the transmission in the first loop using different absorbers. It can be shown that the visibility becomes exactly 1 using a phase shifter in the second loop. In this case the phase shifter in the second loop must be strongly correlated to the transmission coefficient of the absorber in the first loop. Using such a device homodyne-like measurements of very weak signals should become possible.Comment: 12 pages, 9 figures, accepted for publication in the Journal of Optics B - Quantum and Semiclassical Optic

Outline of the SECOQC Quantum-Key-Distribution Network in Vienna

A Quantum Key Distribution (QKD) network is currently implemented in Vienna by integrating seven QKD-Link devices that connect five subsidiaries of SIEMENS Austria. We give an architectural overview of the network and present the enabling QKD-technologies, as well as the novel QKD network protocols.Comment: 10 pages, 5 figure

Practical Quantum Key Distribution with Polarization-Entangled Photons

We present an entangled-state quantum cryptography system that operated for the first time in a real world application scenario. The full key generation protocol was performed in real time between two distributed embedded hardware devices, which were connected by 1.45 km of optical fiber, installed for this experiment in the Vienna sewage system. The generated quantum key was immediately handed over and used by a secure communication application.Comment: 5 pages, 3 figure

History of the World Sleep Day

BackgroundSleep has also been cherished by society as a basic human need with a crucial importance for human health. People spend around one third of their lives sleeping. Nowadays, it has never been harder to achieve a restful sleep. When sleep is better understand, that will lessen the drawbacks of the different sleep disorders. Healthy sleep is important for maintaining physical and mental health in adult individuals. Sleep deprivation poses a significant risk for the individual and leads to psychological conditions, such as depression and anxiety. Several sleep disorders are known to the science. If breathing during sleep is not regular, a case of obstructive sleep apnea (OSA) may have been diagnosed.The World Sleep Day is traditionally celebrated in March, on the Friday before the Spring vernal equinox of each year. It is a global awareness and internationally recognized event, organized annually since 2008 by the World Sleep Day Committee of the World Sleep Society. Organizers aim to raise awareness of the problems with proper sleep, sleep disorders and aspects connected to it – medical, social, educational and others.MethodsScientific databases – PubMed, SCOPUS and MEDLINE were used to search for the information targeted. The following keywords – World Sleep Day, history, events, prophylaxis, sleep disorders were used. Information from the official websites of the societies involved in celebrating World Sleep Day was included as well.The aim of the following article is to study the history of the event from its foundation till today, aiming to stress out its usefulness.Results and discussionWorld Sleep Days has been internationally celebrated since 2008 for 15 years now. Since 2016, Bulgaria actively participates in all events organized by the World Sleep Society – Scientific symposiums, prophylactic check-ups for obstructive sleep apnea, elective disciplines in the teaching of students are organized. Importance is put on informing society about the dangers of undiagnosed and untreated sleep disorders, especially sleep apnea. Sleep medicine and Dental Sleep medicine are not recognized as medical specialties in the Republic of Bulgaria.ConclusionsProblems of sleep are extremely common in our days. The situation is continuously being worsened due to the hyperconnectivity people experience with the glowing computer and mobile phone screens. It is admirable that specialists in the field and society try to raise awareness and combat the poor sleep quality consequences. Only by doing the abovementioned, alleviation of the undesirable outcomes of irregular sleep can be reached. Legislative measures should be taken in order to certify Sleep medicine and Dental sleep medicine as medical specialties in theRepublic of Bulgaria