Experimental Realization of Optimal Time-Reversal on an Atom Chip for Quantum Undo Operations

The authors report the use of the dressed chopped random basis optimal control algorithm to realize time-reversal procedures. The latter are aimed for the implementation of quantum undo operations in quantum technology contexts as quantum computing and quantum communications. The last performed operation can be time-reversed via the undo command so as to perfectly restore a condition in which any new operation, chosen by the external user, can be applied. By generalizing this concept, the undo command can also allow for the reversing of a quantum operation in a generic time instant of the past. Here, thanks to optimal time-reversal routines, all these functionalities are experimentally implemented on the fivefold (Formula presented.) Hilbert space of a Bose–Einstein condensate of non-interacting 87Rb atoms in the ground state, realized with an atom chip. Each time-reversal transformation is attained by designing an optimal modulated radio frequency field, achieving on average an accuracy of around 92% in any performed test. The experimental results are accompanied by a thermodynamic interpretation based on the Loschmidt echo. These findings are expected to promote the implementation of time-reversal operations in a real scenario of gate-based quantum computing with a more complex structure than the five-level system considered here

Experimental Realization of Optimal Time-Reversal on an Atom Chip for Quantum Undo Operations

We report on the use of the dCRAB optimal control algorithm to realize time-reversal procedures for the implementation of quantum undo operations, to be applied in quantum technology contexts ranging from quantum computing to quantum communications. By means of the undo command, indeed, the last performed operation can be time-reversed so as to perfectly restore a condition in which an arbitrary new operation, chosen by the external user, can be applied. Moreover, by further generalizing this concept, the undo command can also allow for the reversing of a quantum operation in a generic instant of the past. Here, thanks to optimal time-reversal routines, all these functionalities are experimentally implemented on the five-fold F=2 Hilbert space of a Bose-Einstein condensate (BEC) of non-interacting $^{87}$Rb atoms in the ground state, realized with an atom chip. Specifically, each time-reversal transformation is attained by designing an optimal modulated radio frequency field, achieving on average an accuracy of around 92% in any performed test. The experimental results are accompanied by a thermodynamic interpretation based on the Loschmidt echo. Our findings are expected to promote the implementation of time-reversal operations in a real scenario of gate-based quantum computing with a more complex structure than the five-level system here considered

Kinematic evaluation of physical impairments of an elite Paralympic karateka

Karate is a Japanese martial art that counts millions of practitioners worldwide and that is spreading also in Paralympic competitions, requiring accurate categories definition for disabled athletes. The aim of the study is to present kinematic data of an elite Paralympic karateka, in comparison with able-bodied athletes. The authors also aim to promote a better classification within the discipline, based on objective biomechanical evaluations of physical impairments. A male black belt Paralympic karateka (age: 36 y; body weight: 75.5 kg; height: 173 cm) with lower limbs impairments was evaluated. The athlete had been performing high level karate for 20 years before the disability took place. After the post-operative rehabilitation, he attended 3/4 sessions of para- karate training per week. He performed a standardized sequence of movements, involving a sequence of offensive and defensive techniques, (kata) from traditional Shotokan karate. Joints and body Center of Mass (CoM) kinematics were collected with an optoelectronic motion capture system and compared with those obtained in two groups of able-bodied (elite and amateurs) athletes from a previous study1. Knee angular range of motion (RoM) and peak angular velocity were obtained. Coordinates of CoM were estimated, using the Segmental Centroid Method2, along with CoM average velocity and acceleration. To assess differences between Paralympic karateka and able-bodied groups, the one-sample t-test was performed. The sequence performed by the karateka lasted more than in both able-bodied groups. CoM average velocity and acceleration decreased in comparison with elite karateka. Knees range of movement and peak angular velocity were similar to amateur but lower than elite athletes. Results show that the physical impairments negatively affected the function of lower limbs in the Paralympic athlete. Fundamental skills in karate elite performance (dynamic balance control and joint RoM and angular velocity) were reduced

Biceps brachii muscle fatigue during isometric contraction: is antagonist muscle fatigue a key factor?

Abstract: Purpose: Several studies analyzed muscle activity after pre-fatigue due to co-contraction, but the effects of antagonist contraction on agonist muscle performance are still incompletely known. The purpose is to determine if a previous workout of an antagonist muscle can affect muscular fatigue appearance during the subsequent agonist muscle performance. Methods: Surface EMG was used to estimate biceps brachii muscle fatigue during isometric contraction executed after previous contractions of the antagonist muscle. Eight expert male body-builders performed five series of isometric contractions (30 s) alternatively according to the agonist and antagonist protocols. Results: Within each repetition, for both biceps brachii muscles and experimental protocols, data showed a progressive fatigue, but no continuous quantitative decreasing trend of the median frequency of the spectrum along the five repetitions. Contraction time explained 1-91% (r2 values) of the reduction of mean activation frequency along the 30 s(agonistic protocol); 0.7-92% for antagonistic protocol. The decrement in median frequency was only partially time\u2013related. A repeated measures Anova found significant differences between subjects (p<0.0001), protocols (antagonistic greater than agonistic, p=0.03), while between sides (p=0.93) and repetitions (p=0.50), and for all interactions no significant differences were found. Conclusion: The present results did not confirm that the antagonistic pre-fatiguing can delay the fatigue appearance during agonistic performance (isometric tasks). Accordingly, the antagonistic protocol does not seem to be functional in improving the upper arm performance from a fatigue point of view, at least in trained subjects

Anthropometric characteristic and running parameters: speed performance of children

This contribution deals with speed abilities of the pupils in short-distance runs in athletics. In scientific literature there are lots of studies that analyze speed performance in adults. These studies showed the correlation between speed and anthropometric measurements and between performance and indicators of speed (acceleration, frequency and length of steps). The aim of our study was the description of speed performance about children to verify similar relation as found in adults. We investigated speed abilities using the 50 m sprint test with standing start. The sample of subject consisted of 90 male and female pupils (45 male and 45 female) aged between 6 and 8 years old: beginner in athletic practice. We analyze performance with chronometers and photocells and we collected for each subject the anthropometric measurements (weight, height, torso and lower limb length), total time, intercepts every 10 meters and frequency of the step every 10 meters. The Anova 1 Way and Tukey-Kramer post hoc test was used to verify if the results were statistically significant among intercepts. In general, boys run faster than girl, total time decrease as the age increase and the interpretation and management of the effort in sprint change in the different age. Furthermore, the correlation between speed and anthropometric measurements were not always verified and the 20 meter cut-off was the general point where the run decreased. In conclusion, the performance in children could be improved using technical exercises about the support phases and educational approach to extend the effort

Patient preferences for emergency department-initiated tobacco interventions: a multicenter cross-sectional study of current smokers

BACKGROUND: The emergency department (ED) visit provides a great opportunity to initiate interventions for smoking cessation. However, little is known about ED patient preferences for receiving smoking cessation interventions or correlates of interest in tobacco counseling. METHODS: ED patients at 10 US medical centers were surveyed about preferences for hypothetical smoking cessation interventions and specific counseling styles. Multivariable linear regression determined correlates of receptivity to bedside counseling. RESULTS: Three hundred seventy-five patients were enrolled; 46% smoked at least one pack of cigarettes per day, and 11% had a smoking-related diagnosis. Most participants (75%) reported interest in at least one intervention. Medications were the most popular (e.g., nicotine replacement therapy, 54%), followed by linkages to hotlines or other outpatient counseling (33-42%), then counseling during the ED visit (33%). Counseling styles rated most favorably involved individualized feedback (54%), avoidance skill-building (53%), and emphasis on autonomy (53%). In univariable analysis, age (r = 0.09), gender (average Likert score = 2.75 for men, 2.42 for women), education (average Likert score = 2.92 for non-high school graduates, 2.44 for high school graduates), and presence of smoking-related symptoms (r = 0.10) were significant at the p \u3c 0.10 level and thus were retained for the final model. In multivariable linear regression, male gender, lower education, and smoking-related symptoms were independent correlates of increased receptivity to ED-based smoking counseling. CONCLUSIONS: In this multicenter study, smokers reported receptivity to ED-initiated interventions. However, there was variability in individual preferences for intervention type and counseling styles. To be effective in reducing smoking among its patients, the ED should offer a range of tobacco intervention options

The estimation of body center of mass kinematics in sport: proposal of a new protocol

The assessment of body Center of Mass (CoM) kinematics is an important measure in the analysis of sport movements since it is strictly related to balance and stability control [1]. Among the methods proposed to estimate CoM displacement, Segmental method appears to be suitable to investigate CoM kinematics in sport: human body is assumed as a system of rigid segments, and the whole-body CoM is calculated as the weighted average of the CoM of each segment. Each segment is defined by a set of landmarks, and their overall number represents a crucial choice in the protocol design process, being a compromise between accuracy and invasivity [2]. In the present study, using a motion capture system, we validated a protocol based upon the Segmental method, adopting a 14-landmarks anatomical model. Two sets of experiments were made. At first, our protocol was compared to the Ground Reaction Force method (GRF), accounted as a golden standard in CoM estimation. Subsequently, we investigated the aerial phase typical of many sports, comparing our protocol with: (1) an absolute reference, the parabolic regression of the vertical CoM trajectory during the time of flight; (2) two common approaches to estimate CoM kinematics in gait, known as Sacrum and Reconstructed Pelvis methods. Recognized accuracy indexes proved that the results obtained were comparable to the GRF; what is more, during the aerial phase our protocol showed to be significantly more accurate than the other two methods. The protocol assessed can therefore be adopted as a reliable tool for CoM kinematics estimation in further sport researches

Dribbling skill determinants in youth soccer players

Dribbling and pass-kick are the most frequently performed techniques during match play. While an extensive knowledge is available about kicking biomechanics, little is known about dribbling kinematics. Given that dribbling performance can assist in the talent identification process [1], we aim at finding the biomechanics determinants of this technique. A motion analysis system recorded the 3-D coordinates of 21 reflective markers placed upon the body of 10 youth sub-elite soccer players (12.6±0.37 years, 42.9±6.15 kg, 1.54 ± 0.07 m). Each participant performed 5 slalom-dribbling tests consisting of a 180° turning and four changes of direction. Since dribbling speed is a separating performance factor, players were split into two groups of 5 according to the execution time (“fast” and “slow”). Center of Mass (CoM) trajectory, Range of Motion (RoM), velocity and acceleration were computed along the three directions [2]. Mann-Whitney’s non-parametric tests were used for comparisons. Fast and slow players did not differ in terms of age, weight, body height, BMI, playing position and number of foot-ball contacts (p&gt;0.05). While CoM average velocity and root mean square acceleration were similar in the two groups, CoM mediolateral and craniocaudal RoM were significantly lower (p&lt;0.05) in faster players. Skilled players took less time in completing the test because they were able to drive the ball while running through a shorter path. Their CoM vertical and lateral displacements were significantly lower, meaning that, at a higher skill level, dribbling technique is delivered in a more effective and economical way

Body center of mass displacements during walking with low- and high-heeled shoes

Walking is a natural activity that is very often performed wearing shoes. Among many other kinds of footwear, high-heeled shoes induce increased ankle plantar flexion, greater knee flexion, anterior pelvic tilt, and trunk extension [1]. The modifications in the arrangement of body segments cause an altered position of the body centre of mass (CoM). In the current study, we quantitatively compared the 3D displacement of CoM during flat-heeled and high-heeled gait. Eleven volunteer women (mean age, 24 years) walked wearing either low-heeled and high-heeled shoes (minimum height, 70 mm). On each subject, the 3D coordinates of 14 body landmarks were recorded by an optoelectronic motion analyzer. The body was segmented in 10 independent masses: head, torso, two upper arms and two lower arms (upper body); two upper legs and two lower legs (lower body). Using mean anthropometric data, the whole body CoM was computed, as well as its superior (uCoM) and inferior (iCoM) components [2]. The body CoM was evaluated during normalized stride cycles. High-heeled gait, compared to flat-heeled gait, had a significantly lower CoM at Right heel strike (p=0.024) and Left heel strike (p=0.030). The same findings were also observed for uCoM and iCoM. No significant differences were found at Right toe off. In addition, a significant forward displacement of the iCoM in high-heeled gait was observed at each of the three stages (R heel strike, p=0.017; L heel strike, p=0.034; R toe off, p=0.003). Similar results were found for the whole CoM (p=0.024, p=0.038, p=0.004). The uCoM in high-heeled gait, instead, was significantly more anterior than in flat-heeled gait only at R toe off (p=0.024). Our findings confirmed that wearing high-heeled shoes significantly alters the normal displacement of both components of the human CoM

Physical performance in high school students: effect of chronotype

Morningness-Eveningness (M-E) is an individual characteristic, defined as chronotype. People are typically categorized in 3 different chronotypes: Morning, Evening and Neither types (M, E and N-types), which differ in the circadian rhythm of many physiological variables. M-types use to wake up and go to bed early and to have their best performances in the first part of the day, otherwise E-types go to bed and wake up late and they have the peak performances in the evening. The chronotype is influenced by both individual and environmental factors and gradually changes during human development. Many studies have demonstrated a trend beginning with a tendency toward morningness in children that gradually evolves into a shift toward eveningness. Approximately at the age of 20 years, this shift reaches its maximum and starts to decline, leading to a growing tendency toward morningness from midadulthood on. This more pronounced eveningness has been found to negatively affect adolescents’ sleep and daytime functioning; even physical performance of adolescents can vary throughout the day because sleep pressure increases, the input from the circadian timing system is optimal or non-optimal to perform the task or both of them. In this study participated 216 students, 124 males and 92 females, attending the first two high school classes (mean age 14-15 years). For the assessment of chronotype, all students compiled the Morningness-Eveningness Questionaire (MEQ), validated by Horne and Ostberg in 1976. For all subjects we collected anthropometric data (weight, height, BMI). All the subjects were categorized as M (n=22), N (n=165), and E-types (n=29). To assess the relationship between chronotype and physical performance, from the sample we recruited 51 subjects, 22 M-type (14 males and 8 females) and 29 E-types (18 males and 11 females), who carried out three Eurofit tests (SHR, Shuttle Run; SBJ, Standing Broad Jump; Cooper endurance test). Preliminary results, although showing some differences in physical performance between E and M chronotype, have not detected statistically significant differences between the two groups