Generating spatially entangled itinerant photons with waveguide quantum electrodynamics.

Realizing a fully connected network of quantum processors requires the ability to distribute quantum entanglement. For distant processing nodes, this can be achieved by generating, routing, and capturing spatially entangled itinerant photons. In this work, we demonstrate the deterministic generation of such photons using superconducting transmon qubits that are directly coupled to a waveguide. In particular, we generate two-photon N00N states and show that the state and spatial entanglement of the emitted photons are tunable via the qubit frequencies. Using quadrature amplitude detection, we reconstruct the moments and correlations of the photonic modes and demonstrate state preparation fidelities of 84%. Our results provide a path toward realizing quantum communication and teleportation protocols using itinerant photons generated by quantum interference within a waveguide quantum electrodynamics architecture.

Biomarkers and prediction of myocardial triglyceride content in non-diabetic men.

BACKGROUND AND AIMS: Lipid oversupply to cardiomyocytes or decreased utilization of lipids leads to cardiac steatosis. We aimed to examine the role of different circulating metabolic biomarkers as predictors of myocardial triglyceride (TG) content in non-diabetic men. METHODS AND RESULTS: Myocardial and hepatic TG contents were measured with 1.5 T magnetic resonance (MR) spectroscopy, and LV function, visceral adipose tissue (VAT), abdominal subcutaneous tissue (SAT), epicardial and pericardial fat by MR imaging in 76 non-diabetic men. Serum concentration of circulating metabolic biomarkers [adiponectin, leptin, adipocyte-fatty acid binding protein 4 (A-FABP 4), resistin, and lipocalin-2] including ß-hydroxybuturate (ß-OHB) were measured. Subjects were stratified by tertiles of myocardial TG into low, moderate, and high myocardial TG content groups. Concentrations of ß-OHB were lower (p = 0.003) and serum levels of A-FABP 4 were higher (p < 0.001) in the group with high myocardial TG content compared with the group with low myocardial TG content. ß-OHB was negatively correlated with myocardial TG content (r = -0.316, p = 0.006), whereas A-FABP 4 was not correlated with myocardial TG content (r = 0.192, p = 0.103). In multivariable analyses ß-OHB and plasma glucose levels were the best predictors of myocardial TG content independently of VAT and hepatic TG content. The model explained 58.8% of the variance in myocardial TG content. CONCLUSION: Our data showed that ß-OHB and fasting glucose were the best predictors of myocardial TG content in non-diabetic men. These data suggest that hyperglycemia and alterations in lipid oxidation may be associated with cardiac steatosis in humans.

Thermal and Residual Excited-State Population in a 3D Transmon Qubit.

Remarkable advancements in coherence and control fidelity have been achieved in recent years with cryogenic solid-state qubits. Nonetheless, thermalizing such devices to their milliKelvin environments has remained a long-standing fundamental and technical challenge. In this context, we present a systematic study of the first-excited-state population in a 3D transmon superconducting qubit mounted in a dilution refrigerator with a variable temperature. Using a modified version of the protocol developed by Geerlings et al., we observe the excited-state population to be consistent with a Maxwell-Boltzmann distribution, i.e., a qubit in thermal equilibrium with the refrigerator, over the temperature range 35-150 mK. Below 35 mK, the excited-state population saturates at approximately 0.1%. We verified this result using a flux qubit with ten times stronger coupling to its readout resonator. We conclude that these qubits have effective temperature T(eff)=35 mK. Assuming T(eff) is due solely to hot quasiparticles, the inferred qubit lifetime is 108 µs and in plausible agreement with the measured 80 µs.

Driven dynamics and rotary echo of a qubit tunably coupled to a harmonic oscillator.

We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence.

Phonon-mediated back-action of a charge readout on a double quantum dot.

Quantum point contacts are in use as an on-chip capacitative readout for the charge state of quantum dot systems. Here we investigate experimentally the back-action of quantum point contacts (QPCs) on a nearby double quantum dot (DQD). Driving current through a QPC influences the DQD state and leads to a measurable current flow in the DQD circuit with no bias voltage applied. The responsible mechanism is an indirect back-action process due to ohmic heating of the phonon bath. The system behaves like a thermoelectric engine, where a temperature gradient between the phonon bath and the electronic bath generates work observable as a measurable current flowing through the DQD.

Time-resolved detection of single-electron interference.

We demonstrate real-time detection of self-interfering electrons in a double quantum dot embedded in an Aharonov-Bohm interferometer, with visibility approaching unity. We use a quantum point contact as a charge detector to perform time-resolved measurements of single-electron tunneling. With increased bias voltage, the quantum point contact exerts a back-action on the interferometer leading to decoherence. We attribute this to emission of radiation from the quantum point contact, which drives noncoherent electronic transitions in the quantum dots.

Chromosomal damage in two X-ray irradiated cell lines: influence of cell cycle stage and irradiation temperature.

UNLABELLED: The aim of this study was to investigate if irradiation with X-rays in different cell cycle phases resulted in a different response as measured with the micronucleus technique. In addition, the influence of irradiation temperature was investigated. MATERIALS AND METHODS: Cells from a non-transformed human fibroblast cell line, HS2429, and a human breast cancer cell line, MCF-7, were synchronized by thymidine block and irradiated at either 2 degrees C or 37 degrees C in the G1-, S- and G2/M-phases. After cytokinesis-block by cytochalasin B, the frequency of micronuclei was determined. RESULTS: Clear dose-response relationships were found. More micronuclei were detected in fibroblast cells irradiated in G1 and S than in G2/M, while the differences were not as prominent in MCF-7 cells. The irradiation temperature had no significant influence on the formation of micronuclei in either of the cell lines. CONCLUSION: The formation of micronuclei varies with the cell cycle stage at the time of irradiation.

Frequency-selective single-photon detection using a double quantum dot.

We use a double quantum dot as a frequency-tunable on-chip microwave detector to investigate the radiation from electron shot-noise in a near-by quantum point contact. The device is realized by monitoring the inelastic tunneling of electrons between the quantum dots due to photon absorption. The frequency of the absorbed radiation is set by the energy separation between the dots, which is easily tuned with gate voltages. Using time-resolved charge-detection techniques, we can directly relate the detection of a tunneling electron to the absorption of a single photon.

Counting statistics of single electron transport in a quantum dot.

We have measured the full counting statistics of current fluctuations in a semiconductor quantum dot (QD) by real-time detection of single electron tunneling with a quantum point contact. This method gives direct access to the distribution function of current fluctuations. Suppression of the second moment (related to the shot noise) and the third moment (related to the asymmetry of the distribution) in a tunable semiconductor QD is demonstrated experimentally. With this method we demonstrate the ability to measure very low current and noise levels.

Detection of mild emphysema by computed tomography density measurements.

PURPOSE: To assess the ability of a conventional density mask method to detect mild emphysema by high-resolution computed tomography (HRCT); to analyze factors influencing quantification of mild emphysema; and to validate a new algorithm for detection of mild emphysema. MATERIAL AND METHODS: Fifty-five healthy male smokers and 34 never-smokers, 61-62 years of age, were examined. Emphysema was evaluated visually, by the conventional density mask method, and by a new algorithm compensating for the effects of gravity and artifacts due to motion and the reconstruction algorithm. Effects of the reconstruction algorithm, slice thickness, and various threshold levels on the outcome of the density mask area were evaluated. RESULTS: Forty-nine percent of the smokers had mild emphysema. The density mask area was higher the thinner the slice irrespective of the reconstruction algorithm and threshold level. The sharp algorithm resulted in increased density mask area. The new reconstruction algorithm could discriminate between smokers with and those without mild emphysema, whereas the density mask method could not. The diagnostic ability of the new algorithm was dependent on lung level. At about 90% specificity, sensitivity was 65-100% in the apical levels, but low in the rest of the lung. CONCLUSION: The conventional density mask method is inadequate for detecting mild emphysema, while the new algorithm improves the diagnostic ability but is nevertheless still imperfect.

Randomized clinical trial of hand-assisted laparoscopic versus open Roux-en-Y gastric bypass for the treatment of morbid obesity.

BACKGROUND: : Roux-en-Y gastric bypass (RYGBP) has increased in popularity since the introduction of the laparoscopic procedure, but this approach requires extensive surgical skill and the learning curve is steep. The present study examined the suitability of hand-assisted laparoscopy for RYGBP. METHODS: In a prospective trial, 50 patients (median age 38 years, body mass index 45 kg/m(2)) were randomized to either hand-assisted (n = 25) or open (n = 25) RYGBP. The hand-assisted device was introduced through a right subcostal incision. Laparoscopic staplers were also used in the open group, allowing a short upper midline incision. The gastrojejunostomy was made by means of a circular stapler and the Roux limb placed behind the colon and excluded stomach. RESULTS: The postoperative outcome, with respect to morphine consumption, complications, hospital stay (6 days) and weight loss, was similar in the two groups. The operating time was significantly longer in the hand-assisted group (150 versus 85 min; P < 0.001) but there was no conversion to open operation. One patient in the hand-assisted group was reoperated owing to leakage and one patient developed an incisional hernia after open RYGBP. CONCLUSION: The hand-assisted technique was feasible and allowed good working conditions in all patients. However, the postoperative outcome was excellent in both groups and there was no advantage to the hand-assisted technique.

On visual determination of full inspiration on CT images.

The aim of this study was to evaluate the ability of experienced thoracic radiologists to assess full inspiration based on two CT slices, one above and one below the carina, in normal subjects. Ten healthy volunteers were studied. Total lung capacity (TLC) was measured with a body plethysmograph. High-resolution computed tomography (HRCT) was performed in two slices at TLC and at various expired volumes. Mean Hounsfield values (HU) were calculated. Unidentifiable images, stored on a web server, were analysed visually by experienced thoracic radiologists. The results show that the mean lung density at TLC varied by approximately 40 HU between individuals. Within an individual this may correspond to a decrease in lung volume of approximately 25% of TLC. On visual determination of images taken at 65-74% of TLC, more than one-third of the images were assessed as taken at full inspiration; of the images taken at 75-84% of TLC, approximately 50% were assessed as taken at full inspiration. We conclude that visual determination of full inspiration on CT images in normal subjects is highly inaccurate. If quantitative density measurements are to be used in the diagnosis or follow-up of lung disease, thorough control of full inspiration is recommended.

Laparoscopic antireflux surgery in routine hospital care.

BACKGROUND: The frequency of antireflux surgery has tripled since laparoscopic techniques were introduced. In Sweden, laparoscopic antireflux surgery is often done at local hospitals with a very low annual number of patients. Many surgeons. who may have limited experience with conventional antireflux surgery, have started to perform laparoscopic antireflux procedures, in spite of the well-known fact that there is a long learning curve for laparoscopic antireflux surgery. METHODS: A random sample of 225 of 660 patients operated on at high-volume and all 220 patients from low-volume hospitals were identified through a nation-wide register. Outcome 4 years after laparoscopic antireflux surgery was studied using a disease-specific questionnaire. RESULTS: Treatment failures were more common in the high-volume group than among patients operated on at low-volume hospitals, 29.0% and 19.7%, respectively. In the high volume group, medication (specifically to relieve heartburn or acid regurgitation) was taken at least once a week and revisional surgery was found in 19.5% and 6.0%, respectively. Corresponding results in the low-volume group were 11.1% and 2.9%, respectively. None of these differences was statistically significant at the overall 0.05 level. CONCLUSION: A failure rate of almost 30% at 4 years' follow-up for patients operated on at relatively high-volume hospitals was disappointing, despite the fact that these results are population-based. Hospitals are encouraged to provide accounts of their results in an effort to identify the reasons for treatment failures, and for the public to have access to more objective information on different therapeutic options.

Long-term results of antireflux surgery indicate the need for a randomized clinical trial.

BACKGROUND: Well conducted, comparative trials of laparoscopic versus open antireflux surgery with an adequate patient enrollment are few and they do not demonstrate obvious advantages for the laparoscopic approach except for a marginal gain in shorter hospital stay. The aim of this study was to compare the effectiveness of laparoscopic and open procedures. METHODS: Two unselected groups of 230 patients were identified through a register of all inpatient public care in Sweden. Outcomes of laparoscopic and open antireflux surgery were compared using a disease-specific questionnaire 4 years after operation. RESULTS: Failure and dissatisfaction were significantly more common in the laparoscopy group than among patients having conventional open surgery. Treatment failure rates were 29.0 and 14.6 per cent respectively (P = 0.004). Dissatisfaction rates were 15.0 and 7.0 per cent respectively (P = 0.005). There was no other questionnaire item for which the proportion of failures differed significantly between the two groups. CONCLUSION: This study does not support the presumption that laparoscopic antireflux surgery is to be preferred to the open procedure. It is strongly recommended that a randomized controlled trial be conducted.

A Swedish study of chemoradiation in squamous cell carcinoma of the esophagus.

This multicenter study describes the development of a chemoradiation protocol for the treatment of non-metastatic squamous cell carcinoma of the esophagus. Eighty patients were treated with three courses of chemotherapy (cisplatinum and 5-fluorouracil) with concomitant radiotherapy (40 Gy) during the last two courses of chemotherapy. Esophagectomy was performed, when feasible. If no operation was performed, patients were planned to receive a target dose of 64 Gy. Toxicity was mainly attributable to hematological impairment and led to two adjustments of the treatment protocol (addition of filgrastim and lowering of the 5-fluorouracil dose). These changes made it possible to administer the planned treatment in a gradually higher proportion of patients (13/23 [57%] before changes of treatment compared with 30/36 [83%] after changes). Treatment-related mortality was 3.75% (3 patients, associated with leucopenic septicemia after chemotherapy). Fifty-four patients were resected. No per- or postoperative mortality was encountered. The complete response (pathological CR) rate in operated patients was 46% (27/59 patients) after chemoradiation. In the whole series the CR rate (including clinical CR for non-resected patients) was 44%. With a minimum follow-up of 37 months, the 3-year survival for the whole group was 31% compared with 57% for the CR patients. Total 5-year survival thus far (July 1999) is 26%.

The complete set of genes encoding major intrinsic proteins in Arabidopsis provides a framework for a new nomenclature for major intrinsic proteins in plants.

Major intrinsic proteins (MIPs) facilitate the passive transport of small polar molecules across membranes. MIPs constitute a very old family of proteins and different forms have been found in all kinds of living organisms, including bacteria, fungi, animals, and plants. In the genomic sequence of Arabidopsis, we have identified 35 different MIP-encoding genes. Based on sequence similarity, these 35 proteins are divided into four different subfamilies: plasma membrane intrinsic proteins, tonoplast intrinsic proteins, NOD26-like intrinsic proteins also called NOD26-like MIPs, and the recently discovered small basic intrinsic proteins. In Arabidopsis, there are 13 plasma membrane intrinsic proteins, 10 tonoplast intrinsic proteins, nine NOD26-like intrinsic proteins, and three small basic intrinsic proteins. The gene structure in general is conserved within each subfamily, although there is a tendency to lose introns. Based on phylogenetic comparisons of maize (Zea mays) and Arabidopsis MIPs (AtMIPs), it is argued that the general intron patterns in the subfamilies were formed before the split of monocotyledons and dicotyledons. Although the gene structure is unique for each subfamily, there is a common pattern in how transmembrane helices are encoded on the exons in three of the subfamilies. The nomenclature for plant MIPs varies widely between different species but also between subfamilies in the same species. Based on the phylogeny of all AtMIPs, a new and more consistent nomenclature is proposed. The complete set of AtMIPs, together with the new nomenclature, will facilitate the isolation, classification, and labeling of plant MIPs from other species.

Hand-assisted laparoscopic bariatric surgery.

Bariatric surgery implies a major life-long rearrangement of the gastrointestinal tract to obtain a controlled weight reduction in a severe but nonmalignant disease. Obesity poses a special challenge to the laparoscopic surgeon. Laparoscopy is known to facilitate the perioperative phase for the patient, but is technically difficult to perform in morbidly obese subjects. Hand-assistance adds extra control in demanding procedures, and Hand-port systems for use in the thick abdominal wall are now available. Here we review the role of hand-assisted laparoscopy for common bariatric procedures and describe our technique for Hand-assisted laparoscopic Roux-en-Y Gastric bypass. Hand-assistance might be the well-blended mix for complex laparoscopic procedures in bariatric work, especially for surgeons working outside highly specialized laparoscopic centers.

Laparoscopic vs open Roux-en-Y gastric bypass: a prospective, randomized trial.

BACKGROUND: The feasibility of laparoscopic Roux-en-Y gastric bypass (Lap-RYGBP) for morbid obesity is well documented. In a prospective randomized trial, we compared laparoscopic and open surgery. METHODS: 51 patients (48 females, mean (+/- SD) age 36 +/- 9 years and BMI 42 +/- 4 kg/m2) were randomly allocated to either laparoscopy (n = 30) or open surgery (n = 21). All patients were followed for a minimum of 1 year. RESULTS: In the laparoscopy group, 7 patients (23%) were converted to open surgery due to various procedural difficulties. In an analysis, with the converted patients excluded, the morphine doses used postoperatively were significantly (p < 0.005) lower in the laparoscopic group compared to the open group. Likewise, postoperative hospital stay was shorter (4 vs 6 days, p < 0.025). Six patients in the laparoscopy group had to be re-operated due to Roux-limb obstruction in the mesocolic tunnel within 5 weeks. The weight loss expressed in decrease in mean BMI units after 1 year was 14 +/- 3 and 13 +/- 3 after laparoscopy and open surgery, respectively (not significant). CONCLUSIONS: Both laparoscopic and open RYGBP are effective and well received surgical procedures in morbid obesity. Reduced postoperative pain, shorter hospital stay and shorter sick-leave are obvious benefits of laparoscopy but conversions and/or reoperations in 1/4 of the patients indicate that Lap-RYGBP at present must be considered an investigational procedure.

Investigation of the excluded stomach after Roux-en-Y gastric bypass.

BACKGROUND: One problem with Roux-en-Y gastric bypass (RYGBP) is that it leaves the bypassed segment not readily available for endoscopic or radiographic examinations. MATERIALS AND METHODS: Three males, 50, 54 and 64 years old, suffered from repeated, gastrointestinal bleeding of unknown origin requiring transfusion 1/2, 1 and 7 years after RYGBP. Access to the stomach was obtained by an ultrasound-guided percutaneous gastrostomy. RESULTS: We could perform endoscopy, barium studies and gastric acid output measurements through the gastrostomy. Histological gastritis, low acid output and absence of H. pylori infection were found. CONCLUSION: We were able to exclude severe gastric disease in our patients.

Attitudes toward older people among nursing students and registered nurses in Sweden.

Geriatric nursing is generally not considered to be a popular branch of nursing among Swedish nursing students and registered nurses. It is, therefore, important for nurse educators and others with responsibilities for the development of nursing to pay attention to trends of importance for the care of the elderly. Attitudes - conceptualized as feelings, knowledge, and readiness to act - may be one important factor. It has been reported that feelings toward older people may change with experience, age and gender. The aim of this study was to measure feelings toward older people among nursing students and registered nurses. A convenience sample of 151 undergraduate nursing students and 41 registered nurses in Sweden participated in the study. Data were collected through Kogan's Old People scale. The results confirmed earlier findings and showed that limited previous experience of care of older people, age <25 years, and male gender were significant factors for showing less favourable feelings towards the aged. In the education of nurses, goal-directed experience of elderly care is recommended in order to create positive feelings towards and interest in older people among students. It is also suggested that special considerations should be given to very young students and male students.