We present a two-state practical quantum bit commitment protocol, the security of which is based on the current technological limitations, namely the non-existence of either stable long-term quantum memories, or non-demolition measurements. For an optical realization of the protocol, we model the errors, which occur due to the noise and equipment (source, fibers and detectors) imperfections, accumulated during emission, transmission and measurement of photons. The optical part is modeled as a combination of a depolarizing channel (white noise), unitary evolution (e.g. systematic rotation of the polarization axis of photons) and two other basis-dependent channels, the phase-and the bit-flip channels. We analyze quantitatively the effects of noise using two common information-theoretic measures of probability distribution distinguishability: the fidelity and the relative entropy. In particular, we discuss the optimal cheating strategy and show that it is always advantageous for a cheating agent to add some amount of white noise -the particular effect not being present in standard quantum security protocols. We also analyze the protocol's security when the use of (im)perfect non-demolition measurements and noisy/bounded quantum memories are allowed. Finally, we discuss errors occurring due to a finite detector efficiency, dark counts and imperfect single-photon sources and show to have the same effects as those of standard quantum cryptography.

Neptune Trojans and Plutinos are two subpopulations of trans-Neptunian objects located in the 1:1 and the 3:2 mean motion resonances with Neptune, respectively, and therefore protected from close encounters with the planet. However, the orbits of these two kinds of objects may cross very often, allowing a higher collisional rate between them than with other kinds of trans-Neptunian objects, and a consequent size distribution modification of the two subpopulations. Observational colors and absolute magnitudes of Neptune Trojans and Plutinos show that i) there are no intrinsically bright (large) Plutinos at small inclinations; ii) there is an apparent excess of blue and intrinsically faint (small) Plutinos; and iii) Neptune Trojans possess the same blue colors as Plutinos within the same (estimated) size range do. For the present subpopulations we analyzed the most favorable conditions for close encounters/collisions and address any link there could be between those encounters and the sizes and/or colors of Plutinos and Neptune Trojans. We also performed a simultaneous numerical simulation of the outer Solar System over 1 Gyr for all these bodies in order to estimate their collisional rate. We conclude that orbital overlap between Neptune Trojans and Plutinos is favored for Plutinos with large libration amplitudes, high eccentricities, and small inclinations. Additionally, with the assumption that the collisions can be disruptive creating smaller objects not necessarily with similar colors, the present high concentration of small Plutinos with small inclinations can thus be a consequence of a collisional interaction with Neptune Trojans and such hypothesis should be further analyzed.

Purpose -In this paper, the aim is to discuss and analyze seasonality of demand within the rural tourist market of North Portugal and corresponding destination marketing implications.Design/methodology/approach -The data (n ¼ 2280) were collected through a large-scale survey in the context of a study of the rural tourist market in North Portugal, from 1998 to 1999.Findings -Results reveal statistically significant differences between those coming in the high versus low season, concerning tourist profile, travel behavior, motivations and perceptions of the destination.Research limitations/ implications -The study results may only be valid for the specific rural region studied, which would make replication studies in other rural destinations desirable to take more generalizable conclusions.Practical implications -Understanding seasonal market differences and confronting them with the destination's resources may contribute to the development of more attractive products and correspondingly to the destination's ability to attract and satisfy different types of tourists in different seasons of the year. The capacity to thereby improve the destination experience in the eyes of its tourists and to also manage demand, avoiding excessive crowding in the high season and eventually sub-optimal use of resources in the low, may be an important step for maintaining a sustainable tourism business in rural areas.Originality/value -The paper aims at contributing to the discussion of how to cope with seasonality of tourist demand, considering particularly the specificity of rural destinations and the global aim of sustainable destination development.