Comment on "Perfect imaging with positive refraction in three dimensions"

Leonhard and Philbin [Phys. Rev. A 81, 011804(R) (2010)] have recently constructed a mathematical proof that the Maxwell's fish-eye lens provides perfect imaging of electromagnetic waves without negative refraction. In this comment, we argue that the unlimited resolution is an artifact of having introduced an unphysical drain at the position of the geometrical image. The correct solution gives focusing consistent with the standard diffraction limit

Quantum state estimation with unknown measurements

Improved measurement techniques are central to technological development and foundational scientific exploration. Quantum optics relies upon detectors sensitive to non-classical features of light, enabling precise tests of physical laws and quantum-enhanced technologies such as precision measurement and secure communications. Accurate detector response calibration for quantum-scale inputs is key to future research and development in these cognate areas. To address this requirement quantum detector tomography (QDT) has been recently introduced. However, the QDT approach becomes increasingly challenging as the complexity of the detector response and input space grows. Here we present the first experimental implementation of a versatile alternative characterization technique to address many-outcome quantum detectors by limiting the input calibration region. To demonstrate the applicability of this approach the calibrated detector is subsequently used to estimate non-classical photon number states.Comment: 7 pages, 3 figure

Exciton Beats in GaAs Quantum Wells: Bosonic Representation and Collective Effects

We discuss light-heavy hole beats observed in transient optical experiments in GaAs quantum wells in terms of a free-boson coherent state model. This approach is compared with descriptions based on few-level representations. Results lead to an interpretation of the beats as due to classical electromagnetic interference. The boson picture correctly describes photon excitation of extended states and accounts for experiments involving coherent control of the exciton density and Rayleigh scattering beating.Comment: 4 pages, no figures. Accepted for publication in Solid State Communication

Experimental generation of multi-photon Fock states

We experimentally demonstrate the generation of multi-photon Fock states with up to three photons in well-defined spatial-temporal modes synchronized with a classical clock. The states are characterized using quantum optical homodyne tomography to ensure mode selectivity. The three-photon Fock states are probabilistically generated by pulsed spontaneous parametric down conversion at a rate of one per second, enabling complete characterization in 12 hours.Comment: 9 pages, 5 figure

Magnon squeezing in an antiferromagnet: reducing the spin noise below the standard quantum limit

At absolute zero temperature, thermal noise vanishes when a physical system is in its ground state, but quantum noise remains as a fundamental limit to the accuracy of experimental measurements. Such a limitation, however, can be mitigated by the formation of squeezed states. Quantum mechanically, a squeezed state is a time-varying superposition of states for which the noise of a particular observable is reduced below that of the ground state at certain times. Quantum squeezing has been achieved for a variety of systems, including the electromagnetic field, atomic vibrations in solids and molecules, and atomic spins, but not so far for magnetic systems. Here we report on an experimental demonstration of spin wave (i.e., magnon) squeezing. Our method uses femtosecond optical pulses to generate correlations involving pairs of magnons in an antiferromagnetic insulator, MnF2. These correlations lead to quantum squeezing in which the fluctuations of the magnetization of a crystallographic unit cell vary periodically in time and are reduced below that of the ground state quantum noise. The mechanism responsible for this squeezing is stimulated second order Raman scattering by magnon pairs. Such squeezed states have important ramifications in the emerging fields of spintronics and quantum computing involving magnetic spin states or the spin-orbit coupling mechanism

An Economic Evaluation of the Product Sugar With Special Emphasis on the Abnormal Sugar Market of 1963-1964

The product sugar is studied in detail with special emphasis on supply and demand factors, in an attempt to better understand the abnormal sugar market of 1963-1964. The unusual market fluctuations of that period appear to have been initiated by a statistical imbalance in world supply and demand of sugar. The extent of price fluctuations in the united states during 1963-1964 we accentuated by the inability of current sugar legislation to shield the U.S. market from the world market, and by the openly aggressive purchasing policies followed by the U.S. department of agriculture which further aggravated an already thin and inflated world sugar market. There is also evidence that excessive market activity on the New York Coffee and Sugar Exchange by the nonprofessional group of buyers contributed additional instability to the sugar market, along with the scare buying and hoarding which were common in the U.S. especially during the critical days of 1963

A Study of the Type and Extent of Hearing Loss of Speech Defective Children in the Elementary Schools of Cache County and of the Logan City School Districts

Many articles and textbooks which have recently been written in the field of speech correction indicate that a high percent of all children who have speech defects also have a hearing deficiency. Some even say that a higher percent of these children have hearing deficiencies than do children who are normal in speech. Because of the great interest which has been aroused in the nature of the problems of the speech defectives, and because of the desire which exists for them to be helped in their handicaps, there is a necessity for their problems to be understood as thoroughly as possible. The present investigation has therefore been undertaken to establish the type and extent of hearing loss in the speech defective children in the first six grades of the elementary schools of Cache County and of the Logan City school districts

STRUKTUR BUNYI DALAM TONIS PERPISAHAN PADA MASYARAKAT DAWAN DI KABUPATEN TIMOR TENGAH SELATAN

Penelitian ini bertujuan membahas struktur bunyi yang terkandung dalam tonis perpisahan (tuturan lisan) masyarakat Dawan di Kabupaten Timor Tengah Selatan. Struktur yang dibahas berupa bunyi berjenis aliterasi dan asonansi. Penelitian ini bersifat deskriptif kualitatif dengan data etniik berupa tuturan tonis perpisahan pada masyarakat Dawan di Kabupaten Timor Tengah Selatan. Pengumpulan data dilakukan dengan cara mengobservasi, merekam dan mencatat. Teknik menganalisis secara deskriptif dengan mentranskripsikan data lisan menjadi data tulis, menerjemahkan secara bebas, mengidentifikasi, menafsirkan, dan menguraikan secara detail lalu menarik simpulan. Hasil penelitian menunjukan adanya struktur berupa bunyi asonansi atau pengulangan bunyi vokal [a], [e], [i], [o], dan [u]; bunyi aliterasi yang menderetkan pengulangan bunyi konsonan [m], [n], [k], [l], [h], [t], [b], [l], [s]. Pengulangan-pengulangan bunyi dengan deretan vokal dan konsonan tersebut terkontruksi dengan bervariasi, sehingga menimbulkan grafologi huruf yang homogeni serta memiliki rima lengkap dan rima paruh atau rima sebagian dengan posisi di awal, tengah, maupun akhir kata

Improving food environments and tackling obesity: a realist systematic review of the policy success of regulatory interventions targeting population nutrition

Published: August 4, 2017Background: This systematic review (PROSPERO: CRD42015025276) employs a realist approach to investigate the effect of “real-world” policies targeting different aspects of the food environment that shape individual and collective nutrition. Objectives: We were interested in assessing intermediate outcomes along the assumed causal pathway to “policy success”, in addition to the final outcome of changed consumption patterns. Data sources: We performed a search of 16 databases through October 2015, with no initial restriction by language. Study eligibility criteria: We included all publications that reported the effect of statutory provisions aimed at reducing the consumption of energy-dense foods and beverages in the general population. We allowed all methodological approaches that contained some measure of comparison, including studies of implementation progress. Study appraisal and synthesis methods: We reviewed included studies using the appraisal tools for pre-post and observational studies developed by the National Heart, Lung, and Blood Institute. Given the considerable heterogeneity in interventions assessed, study designs employed, and outcome measures reported, we opted for a narrative synthesis of results. Results and implications: Results drawn from 36 peer-reviewed articles and grey literature reports demonstrated that isolated regulatory interventions can improve intermediate outcomes, but fail to affect consumption at clinically significant levels. The included literature covered six different types of interventions, with 19 studies reporting on calorie posting on chain restaurant menus. The large majority of the identified interventions were conducted in the US. Early results from recent taxation measures were published after the review cut-off date but these suggested more favorable effects on consumption levels. Nevertheless, the evidence assessed in this review suggests that current policies are generally falling short of anticipated health impacts.Jana Sisnowski, Jackie M. Street, Tracy Merli