Maximum-likelihood coherent-state quantum process tomography

Coherent-state quantum process tomography (csQPT) is a method of completely characterizing a quantum-optical "black box" by probing it with coherent states and performing homodyne measurements on the output [M. Lobino et al, Science 322, 563 (2008)]. We present a technique for csQPT that is fully based on statistical inference, specifically, quantum expectation-maximization. The method relies on the Jamiolkowski isomorphism and iteratively reconstructs the process tensor in the Fock basis directly from the experimental data. This approach permits incorporation of a priori constraints into the reconstruction procedure, thereby guaranteeing that the resulting process tensor is physically consistent. Furthermore, our method is easier to implement and requires a narrower range of coherent states than its predecessors. We test its feasibility using simulations on several experimentally relevant processes.Comment: 17 pages, 4 figure

Hidden Subsidies

Many governments use price subsidisation (total costs less total revenues from user charges) to meet social protection objectives in lieu of, or in addition to, direct income transfers. Such subsidies may be perceived as influencing behaviour to further other socially desirable policies. For example, the price response induced by lowering the price of schooling will both lower the cost of living for the beneficiaries and also increase the investment in education more than a similar income transfer would achieve. The incidences of benefits from a general price subsidy are proportional to purchases and can be deduced from the pattern of expenditures. Some goods are inappropriate vehicles for redistribution since subsidies on them will not only accrue mainly to the rich they will actually increase inequality in welfare. It is therefore important to ensure that commodities chosen for price subsidisation are largely consumed by the lower income groups. Also, detailed data on such commodities should be made public to make the extent of subsidy easily tractable. In the case of Pakistan, the problem of lack of transparency of federal and provincial budgets is vividly demonstrated by the inability of such budgets to readily highlight the subsidy on the various economic and social services, which are essentially in the nature of ‘private’ goods, provided by such governments. This is not only a reflection of the problem of the nature of budgeting practices whereby, first, revenues and expenditures on different heads are shown separately and no account is made either of depreciation of assets or the costs of capital used to finance the acquisition of assets which yield a stream of services. Second, to the extent that the subsidies largely benefit the upper income groups, political compulsions dictate that such subsidies largely remain hidden.

Transport Through an Electrostatically Defined Quantum Dot Lattice in a Two-Dimensional Electron Gas

Quantum dot lattices (QDLs) have the potential to allow for the tailoring of optical, magnetic and electronic properties of a user-defined artificial solid. We use a dual gated device structure to controllably tune the potential landscape in a GaAs/AlGaAs two-dimensional electron gas, thereby enabling the formation of a periodic QDL. The current-voltage characteristics, I(V), follow a power law, as expected for a QDL. In addition, a systematic study of the scaling behavior of I(V) allows us to probe the effects of background disorder on transport through the QDL. Our results are particularly important for semiconductor-based QDL architectures which aim to probe collective phenomena.Comment: 6 pages, 4 figure

Generalized anxiety disorder: can we rest now?

Generalized anxiety disorder is a complex psychiatric syndrome. Current understanding on the epidemiological risk factors, genetic vulnerability and neurobiology of the GAD is beginning to unfold the complexities behind this disorder. This narrative review has attempted to put together the recent advances in the area of GAD research with intent to identify the gaps requiring further research

Effect of processing condition and composition on the microhardness of Cu-(2.5-10)vol.%Al₂O₃ nanocomposite powder particles produced by high energy mechanical milling

Nanostructured Cu-(2.5-10vol.%)Al₂O₃ nanocomposites were produced using high energy mechanical milling. For the as-milled Cu- Al₂O₃ composite powder particles having Al₂O₃ volume fractions of 2.5% and 5%, the increase in average microhardness is significant with the increase of milling time from 12 hours to 24 hours. With the increase of the content of Al₂O₃ nanoparticles the microhardness increases and in the range of 255HV-270HV. The milled nanocomposite powders were heat treated at 150, 300, 400 and 500°C for 1 hour, respectively, to determine the thermal stability of the powder particles as a function of annealing temperature. The average microhardness increased/decreased for the Cu- Al₂O₃ composites after annealing at 150°C due to the dislocation density, while increasing the annealing temperature to 300°C and 400°C the average microhardness almost remained mostly unchanged. Further increasing the annealing temperature to 500°C causes significant decrease in average microhardness due to reduction in dislocation density and coarsening of Cu grains of the Cu- Al₂O₃ composite powders produced after 24 hours of milling. This paper is to report and discuss the changes of the microhardness of the material, caused by the compositions and processing conditions, used to fabricate the Cu-(2.5-10)vol.% Al₂O₃ nanocomposite powders

Safety and Feasibility of Simultaneous Ipsilateral Proximal Carotid Artery Stenting and Cerebral Aneurysm Coiling

Coexistence of cerebral aneurysm and carotid artery disease may be encountered in clinical practice. Theoretical increase in aneurysmal blood flow may increase risk of rupture if carotid artery disease is treated first. If aneurysm coiling is performed first, stroke risk may increase while repeatedly crossing the diseased artery. It is controversial which disease to treat first, and whether it is safe to treat both simultaneously via endovascular procedures. We document the safety and feasibility of such an approach. Review of collected neurointerventional database at our institution was performed for patients who underwent both carotid artery stenting (CAS) and aneurysm coil embolization (ACE) simultaneously. All patients underwent carotid stenting followed by aneurysm coiling in the same setting. Demographic, clinical data, and outcome measures including success rate and periprocedural complications were collected. Five hundred and ninety aneurysms coiling were screened for patients who underwent combined CAS and ACE. Ten patients were identified. Mean age was 67.7 years (range 51–89). The success rate for stenting and coiling was 100% with no immediate complications. The coiling procedure time was extended by an average of 45 min for performing both procedures jointly. No stroke, TIAs, or aneurysmal rebleeding was found on their most recent follow up. Our case series demonstrates that it is safe and feasible to perform CAS and ACE simultaneously as one procedure which may avoid unwanted risk of treating either disease at two separate time sessions

Optimization of Process Parameters for CNC Turning using Taguchi Methods for EN24 Alloy Steel with Coated/Uncoated Tool Inserts

Coated and uncoated tool inserts offers certain degrees of control on the desired rate of tool wear and surface roughness to an extent. This work pursues the quest for realizing the optimal values for the significant process parameters that bears an influence on the response parameters. Experiments were conducted on the samples of EN 24 alloy steel material with the help of PVD coated TiAlN insert and uncoated carbide insert. The experimental runs carried out with proper variation in the levels. Levels are selected with the help of manufacturing catalogue and by pilot experimentation and results are recorded for further analysis. For this study, 9 runs designed using L9 orthogonal array of Taguchi Design of Experiment. Surface roughness was measured using a Mitutoyo surface tester at test lab and material removal rate is calculated by mathematical equation. The data was compiled into Minitab 17 software for analysis. The relationship between the machining parameters and the response variables were analyzed using the Taguchi Method. Optimization of process parameters is carried out by Grey Relational Analysis method (GRA). GRA method is a powerful and most versatile tool which can manipulate the input data as per requirement and comes with results that can be used to have best multi-objective in respective concerns

Application of impact dampers in vibration control of flexible structures

Impact dampers belong to the category of passive vibration devices used to attenuate the vibration of discrete and continuous systems. An impact damper generally consists of a mass which is allowed to travel freely between two defined stops. Under the right conditions, the vibration of the structure to which the impact damper is attached will cause the mass of the impact damper to strike the structure. Previous analytical and experimental research work on the effect of impact dampers in attenuating the vibration of discrete and continuous systems have demonstrated their effectiveness. It has been shown in this study that impact dampers can increase the intrinsic damping of a lightly-damped flexible structure. The test structure consists of a slender flexible beam supported by a pin-type support at one end and supported by a linear helical flexible spring at another location. Sinusoidal excitation spanning the first three natural frequencies was applied in the horizontal plane. The orientation of the excitation and the test structure in the horizontal plane minimizes the effect of gravity on the behavior of the test structure. The excitation was applied using a linear sine sweep technique. The span of the test structure, the mass of the impact damper, the distance of travel, and the location of the impact damper along the span of the test structure were varied. The damping ratio are estimated for sixty test configurations. The results show that the impact damper significantly increases the damping ratio of the test structure. Statistical analysis of the results using the method of multiple linear regression indicates that a reasonable fit has been accomplished. It is concluded that additional experimental analysis of flexible structures in microgravity environment is needed in order to achieve a better understanding of the behavior of impact damper under conditions of microgravity. Numerical solution of the behavior of flexible structures equipped with impact dampers is also needed to predict stresses and deformations under operating conditions of microgravity in space applications

Hidden Subsidies

Many governments use price subsidisation (total costs less total revenues from user charges) to meet social protection objectives in lieu of, or in addition to, direct income transfers. Such subsidies may be perceived as influencing behaviour to further other socially desirable policies. For example, the price response induced by lowering the price of schooling will both lower the cost of living for the beneficiaries and also increase the investment in education more than a similar income transfer would achieve. The incidences of benefits from a general price subsidy are proportional to purchases and can be deduced from the pattern of expenditures. Some goods are inappropriate vehicles for redistribution since subsidies on them will not only accrue mainly to the rich they will actually increase inequality in welfare. It is therefore important to ensure that commodities chosen for price subsidisation are largely consumed by the lower income groups. Also, detailed data on such commodities should be made public to make the extent of subsidy easily tractable