Photon Sorting, Efficient Bell Measurements and a Deterministic CZ Gate using a Passive Two-level Nonlinearity

Although the strengths of optical non-linearities available experimentally have been rapidly increasing in recent years, significant challenges remain to using such non-linearities to produce useful quantum devices such as efficient optical Bell state analysers or universal quantum optical gates. Here we describe a new approach that avoids the current limitations by combining strong non-linearities with active Gaussian operations in efficient protocols for Bell state analysers and Controlled-Sign gates

Пандемии и налоговые инновации: чему нас учит история?

In this article, we shall see how pandemics of deadly diseases have changed tax systems over the past two millennia, each time leading to the emergence of new forms of taxation and tax administration. The purpose of the article is to prove that pandemics and the most notable innovations in tax policy are closely interrelated and that the consequences of the largest pandemics in the history of mankind are new approaches to the organization of national tax systems as well as the formation of interstate tax regulation. The lessons from history can be applied to the current corona crisis and may help us devise the appropriate anti-crisis tax policy. The study is based on the historical empirical-inductive method applied to reliable facts of the past related to pandemics and taxation. We trace the evolution of tax policy under the impact of the most significant pandemics and identify patterns of taxation and tax administration that are specific to their eras and are still relevant in the course of the pandemic COVID-19. Our analysis allows us to draw the following conclusions: (1) There is a historical link between pandemics and tax regulation. Many tax innovations originated in response to the consequences of large-scale epidemics of deadly diseases. (2) Many of the tax incentive tools used today in the fight against the corona crisis have already been used during previous pandemics so that we may learn from the experience of earlier times. (3) The COVID-19 pandemic can be expected to have several important consequences for taxation and public finance: innovations in tax administration with an emphasis on remote fiscal audits and digital control; innovations in the taxation of digital companies and their operations at the national and international level; possibly fundamental changes in the tax system of the European Union; and possibly a return of the inflation tax.For citationPogorletskiy A.I., Söllner F. Pandemics and Tax Innovations: What can we Learn from History? Journal of Tax Reform. 2020;6(3):270–297. DOI: 10.15826/jtr.2020.6.3.086.Article infoReceived August 25, 2020; Revised September 20, 2020; Accepted October 16, 2020В предлагаемой статье мы выявим воздействие пандемий смертельных болезней на модификацию налоговых систем на протяжении двух последних тысячелетий, что приводило к появлению прогрессивных форм налогообложения и налогового администрирования. Цель статьи– доказать, что пандемии и самые заметные инновации в налоговой политике тесно взаимосвязаны и что последствием самых масштабных пандемий в истории человечества стали новые подходы в организации национальных налоговых систем, а также становление межгосударственного налогового регулирования. Уроки истории могут оказаться полезными в условиях преодоления последствий коронакризиса начала 2020-х гг., помогая разрабатывать соответствующую антикризисную налоговую политику. Исследование основано на историческом эмпирически-индуктивном методе, примененном в отношении достоверных фактов прошлого, связанных с пандемиями и налогообложением. Сравнительный метод осмысления исторических событий позволил авторам сопоставить последствия эволюции налоговой политики под влиянием воздействия наиболее масштабных пандемий инфекционных заболеваний, а также выявить закономерности налогообложения и налогового администрирования, характерные для соответствующих исторических эпох и по-прежнему актуальные в ходе пандемии COVID-19. Проделанный авторами анализ позволяет сделать следующие выводы: (1) существует историческая связь между пандемиями и налоговым регулированием: многие налоговые инновации возникли в ответ на последствия масштабных эпидемий смертельно опасных заболеваний; (2) значительная часть инструментов налогового стимулирования экономики, применяемых в ходе антикризисного регулирования в период пандемии COVID-19, уже использовалась ранее, во время предыдущих пандемий, что позволяет учитывать соответствующие исторические уроки; (3) можно ожидать, что пандемия коронавируса SARS-CoV-2 будет иметь несколько важных последствий для налогообложения и государственных финансов: инновации в налоговом администрировании с акцентом на дистанционный финансовый аудит и цифровой контроль; инновации в налогообложении цифровых компаний и их операций на национальном и международном уровнях; вероятные фундаментальные изменения в налоговой системе Европейского союза; и, возможно, возврат в мировую практику инфляционного налога.Для цитированияПогорлецкий А.И., Зольнер Ф. Пандемии и налоговые инновации: чему нас учит история? // Journal of Tax Reform. – 2020. – Т. 6, № 3. – С. 270–297. – DOI: 10.15826/jtr.2020.6.3.086.Информация о статьеДата поступления 25 августа 2020 г.; дата поступления после рецензирования 20 сентября 2020 г.; дата принятия к печати 16 октября 2020 г

Near-unity coupling efficiency of a quantum emitter to a photonic-crystal waveguide

A quantum emitter efficiently coupled to a nanophotonic waveguide constitutes a promising system for the realization of single-photon transistors, quantum-logic gates based on giant single-photon nonlinearities, and high bit-rate deterministic single-photon sources. The key figure of merit for such devices is the $\beta$-factor, which is the probability for an emitted single photon to be channeled into a desired waveguide mode. We report on the experimental achievement of $\beta = 98.43 \pm 0.04\%$ for a quantum dot coupled to a photonic-crystal waveguide, corresponding to a single-emitter cooperativity of $\eta = 62.7 \pm 1.5$. This constitutes a nearly ideal photon-matter interface where the quantum dot acts effectively as a 1D "artificial" atom, since it interacts almost exclusively with just a single propagating optical mode. The $\beta$-factor is found to be remarkably robust to variations in position and emission wavelength of the quantum dots. Our work demonstrates the extraordinary potential of photonic-crystal waveguides for highly efficient single-photon generation and on-chip photon-photon interaction

Single-photon nonlinear optics with a quantum dot in a waveguide

Strong nonlinear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, nonlinear interactions are usually feeble and therefore all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created . Here we show that a single quantum dot in a photonic-crystal waveguide can be utilized as a giant nonlinearity sensitive at the single-photon level. The nonlinear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon-photon bound state. The quantum nonlinearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures

Characterizing heralded single-photon sources with imperfect measurement devices

Any characterization of a single-photon source is not complete without specifying its second-order degree of coherence, i.e., its $g^{(2)}$ function. An accurate measurement of such coherence functions commonly requires high-precision single-photon detectors, in whose absence, only time-averaged measurements are possible. It is not clear, however, how the resulting time-averaged quantities can be used to properly characterize the source. In this paper, we investigate this issue for a heralded source of single photons that relies on continuous-wave parametric down-conversion. By accounting for major shortcomings of the source and the detectors--i.e., the multiple-photon emissions of the source, the time resolution of photodetectors, and our chosen width of coincidence window--our theory enables us to infer the true source properties from imperfect measurements. Our theoretical results are corroborated by an experimental demonstration using a PPKTP crystal pumped by a blue laser, that results in a single-photon generation rate about 1.2 millions per second per milliwatt of pump power. This work takes an important step toward the standardization of such heralded single-photon sources.Comment: 18 pages, 9 figures; corrected Eq. (11) and the description follows Eq. (22

Spin-photon interface and spin-controlled photon switching in a nanobeam waveguide

Access to the electron spin is at the heart of many protocols for integrated and distributed quantum-information processing [1-4]. For instance, interfacing the spin-state of an electron and a photon can be utilized to perform quantum gates between photons [2,5] or to entangle remote spin states [6-9]. Ultimately, a quantum network of entangled spins constitutes a new paradigm in quantum optics [1]. Towards this goal, an integrated spin-photon interface would be a major leap forward. Here we demonstrate an efficient and optically programmable interface between the spin of an electron in a quantum dot and photons in a nanophotonic waveguide. The spin can be deterministically prepared with a fidelity of 96\%. Subsequently the system is used to implement a "single-spin photonic switch", where the spin state of the electron directs the flow of photons through the waveguide. The spin-photon interface may enable on-chip photon-photon gates [2], single-photon transistors [10], and efficient photonic cluster state generation [11]

Quantitative analysis of quantum dot dynamics and emission spectra in cavity quantum electrodynamics:Paper

We present detuning-dependent spectral and decay-rate measurements to study the difference between spectral and dynamical properties of single quantum dots embedded in micropillar and photonic-crystal cavities. For the micropillar cavity, the dynamics is well described by the dissipative Jaynes-Cummings model, while systematic deviations are observed for the emission spectra. The discrepancy for the spectra is attributed to coupling of other exciton lines to the cavity and interference of different propagation paths towards the detector of the fields emitted by the quantum dot. In contrast, quantitative information about the system can readily be extracted from the dynamical measurements. In the case of photonic crystal cavities we observe an anti crossing in the spectra when detuning a single quantum dot through resonance, which is the spectral signature of strong coupling. However, time-resolved measurements reveal that the actual coupling strength is significantly smaller than anticipated from the spectral measurements and that the quantum dot is rather weakly coupled to the cavity. We suggest that the observed Rabi splitting is due to cavity feeding by other quantum dots and/or multiexcition complexes giving rise to collective emission effects.Comment: 14 pages, 5 figures, submitte

Chirality of nanophotonic waveguide with embedded quantum emitter for unidirectional spin transfer

Scalable quantum technologies may be achieved by faithful conversion between matter qubits and photonic qubits in integrated circuit geometries. Within this context, quantum dots possess well-defined spin states (matter qubits), which couple efficiently to photons. By embedding them in nanophotonic waveguides, they provide a promising platform for quantum technology implementations. In this paper, we demonstrate that the naturally occurring electromagnetic field chirality that arises in nanobeam waveguides leads to unidirectional photon emission from quantum dot spin states, with resultant in-plane transfer of matter-qubit information. The chiral behaviour occurs despite the non-chiral geometry and material of the waveguides. Using dot registration techniques, we achieve a quantum emitter deterministically positioned at a chiral point and realize spin-path conversion by design. We further show that the chiral phenomena are much more tolerant to dot position than in standard photonic crystal waveguides, exhibit spin-path readout up to 95±5% and have potential to serve as the basis of spin-logic and network implementations

A European Research Agenda for Somatic Symptom Disorders, Bodily Distress Disorders, and Functional Disorders : Results of an Estimate-Talk-Estimate Delphi Expert Study

Background: Somatic Symptom Disorders (SSD), Bodily Distress Disorders (BDD) and functional disorders (FD) are associated with high medical and societal costs and pose a substantial challenge to the population and health policy of Europe. To meet this challenge, a specific research agenda is needed as one of the cornerstones of sustainable mental health research and health policy for SSD, BDD, and FD in Europe. Aim: To identify the main challenges and research priorities concerning SSD, BDD, and FD from a European perspective. Methods: Delphi study conducted from July 2016 until October 2017 in 3 rounds with 3 workshop meetings and 3 online surveys, involving 75 experts and 21 European countries. EURONET-SOMA and the European Association of Psychosomatic Medicine (EAPM) hosted the meetings. Results: Eight research priorities were identified: (1) Assessment of diagnostic profiles relevant to course and treatment outcome. (2) Development and evaluation of new, effective interventions. (3) Validation studies on questionnaires or semi-structured interviews that assess chronic medical conditions in this context. (4) Research into patients preferences for diagnosis and treatment. (5) Development of new methodologic designs to identify and explore mediators and moderators of clinical course and treatment outcomes (6). Translational research exploring how psychological and somatic symptoms develop from somatic conditions and biological and behavioral pathogenic factors. (7) Development of new, effective interventions to personalize treatment. (8) Implementation studies of treatment interventions in different settings, such as primary care, occupational care, general hospital and specialty mental health settings. The general public and policymakers will benefit from the development of new, effective, personalized interventions for SSD, BDD, and FD, that will be enhanced by translational research, as well as from the outcomes of research into patient involvement, GP-patient communication, consultation-liaison models and implementation. Conclusion: Funding for this research agenda, targeting these challenges in coordinated research networks such as EURONET-SOMA and EAPM, and systematically allocating resources by policymakers to this critical area in mental and physical well-being is urgently needed to improve efficacy and impact for diagnosis and treatment of SSD, BDD, and FD across Europe