Parameterizing qudit states

Quantum systems with a finite number of states at all times have been a primary element of many physical models in nuclear and elementary particle physics, as well as in condensed matter physics. Today, however, due to a practical demand in the area of developing quantum technologies, a whole set of novel tasks for improving our understanding of the structure of finite-dimensional quantum systems has appeared. In the present article we will concentrate on one aspect of such studies related to the problem of explicit parameterization of state space of an NN-level quantum system. More precisely, we will discuss the problem of a practical description of the unitary SU(N){SU(N)}-invariant counterpart of the NN-level state space BN{\mathcal{B}_N}, i.e., the unitary orbit space BN/SU(N){B_N/SU(N)}. It will be demonstrated that the combination of well-known methods of the polynomial invariant theory and convex geometry provides useful parameterization for the elements of BN/SU(N){B_N/SU(N)}. To illustrate the general situation, a detailed description ofBN/SU(N){B_N/SU(N)} for low-level systems: qubit (N=2{N= 2}), qutrit (N=3{N=3}), quatrit (N=4{N= 4}) - will be given.

International Conference PhysicA.SPb/2021

The International Conference PhysicA. SPb was held 18-22 October 2021 in Saint Petersburg, Russia. The Conference continues the tradition of St.Petersburg Seminars on Physics and Astronomy originating from mid-90s. Since then PhysicA.SPb maintains both scientific and educational quality of contributions delivered to the audience. This is the main feature of the Conference that makes it possible to combine the whole spectrum of modern Physics and Astronomy within one event. PhysicA. SPb/2021 has brought together over 400 academics from many universities and research institutes across whole Russia as well as from USA, UK, South Africa, Poland, Ukraine, Kazakhstan, Belarus, Azerbaijan, and Australia. Oral and poster presentations were combined into well-defined sections among which one should name Astronomy and Astrophysics, Optics and spectroscopy, Physics of ferroics, Nanostructured and thin-film materials, Mathematical physics and numerical methods, Devices and materials for the THz and microwave ranges, Biophysics, Optoelectronic devices, Surface phenomena, Physics and technology of energy conversion, Plasma physics, hydrodynamics and aerodynamics, Nuclear and elementary particle physics, Impurities and defects in solids, Multilayered structures, Spectroscopy of atoms and molecules and Physics of quantum structures. This issue of the Journal of Physics: Conference Series presents the extended contributions from participants of PhysicA.SPb/2021 that were peer-reviewed by expert referees through processes administered by the Presiders of the Organising and Program Committees to the best professional and scientific standards. This was made possible by the efforts of the Sectional and Technical Editors of this Issue: Prof. Petr Arseev (Lebedev Physical Institute), Prof. Alexander Ivanchik (Ioffe Institute), Prof. Polina Ryabochkina (Ogarev Mordova State University), Prof. Yuri Kusraev (Ioffe Institute), Dr. Sergey Nekrasov (Ioffe Institute), Dr. Nikolay Bert (Ioffe Institute), Dr. Nikita Gordeev (Ioffe Institute), Dr. Alexey Popov (Ioffe Institute), Dr. Prokhor Alekseev (Ioffe Institute), Dr. Mikhail Dunaevskii (Ioffe Institute), Prof. Mikhail Nestoklon (Ioffe Institute), Dr. Andrey Dunaev (Orel State University), Prof. Anton Vershovskii (Ioffe Institute), Dr. Vadim Evtikhiev (Ioffe Institute), Prof. Alexey Ustinov (St.Petersburg Electrotechnical University “LETI”), Dr. Alexandra Kalashnikova (Ioffe Institute), Prof. Ivan Mitropolsky (NRC Kurchatov Institute - PNPI), Dr. Evgenia Cherotchenko (Ioffe Institute) and Prof. Dmitry Khokhlov (Moscow State University). The Editors: Nikita S. Averkiev, Sergey A. Poniaev and Grigorii S. Sokolovskii

Millicharged particles from the heavens: single- and multiple-scattering signatures

For nearly a century, studying cosmic-ray air showers has driven progress in our understanding of elementary particle physics. In this work, we revisit the production of millicharged particles in these atmospheric showers and provide new constraints for XENON1T and Super-Kamiokande and new sensitivity estimates of current and future detectors, such as JUNO. We discuss distinct search strategies, specifically studies of single-energy-deposition events, where one electron in the detector receives a relatively large energy transfer, as well as multiple-scattering events consisting of (at least) two relatively small energy depositions. We demonstrate that these atmospheric search strategies — especially the multiple-scattering signature — provide significant room for improvement beyond existing searches, in a way that is complementary to anthropogenic, beam-based searches for MeV-GeV millicharged particles. Finally, we also discuss the implementation of a Monte Carlo simulation for millicharged particle detection in large-volume neutrino detectors, such as IceCube.

Elementary Particle Physics

Determining the nature of matter’s smallest constituents, and the interactions among them, is the subject of a branch of fundamental physics called “The Physics of Elementary Particles” – the subject of this book. During the last decades this field has gone through a phase transition. It culminated in the formulation of a new theoretical scheme, known as “The Standard Model”, which brought profound changes in our ways of thinking and understanding nature’s fundamental forces. Its agreement with experiment is impressive, to the extent that we should no longer talk about “The Standard Model” but instead “The Standard Theory”. This new vision is based on geometry; the interactions are required to satisfy a certain geometrical principle. In the physicists’ jargon this principle is called “gauge invariance”; in mathematics it is a concept of differential geometry. It is the purpose of this book to present and explain this modern viewpoint to a readership of well motivated undergraduate students. We propose to guide the reader to the more advanced concepts of gauge symmetry, quantum field theory and the phenomenon of spontaneous symmetry breaking through concrete physical examples. The presentation of the techniques required for particle physics is self-contained, and the mathematics is kept at the absolutely necessary level. The reader is invited to join the glorious parade of the theoretical advances and experimental discoveries of the last decades which established our current view. Our ambition is to make this fascinating subject accessible to undergraduate students and, hopefully, to motivate them to study it further.

Texture One Zero Model Based on A4 Flavor Symmetry and its Implications to Neutrinoless Double Beta Decay

Neutrinos are perhaps the most elusive particles in our Universe. Neutrino physics could be counted as a benchmark for various new theories in elementary particle physics and also for the better understanding of the evolution of the Universe. To complete the neutrino picture, the missing information whether it is about their mass or their nature that the neutrinos are Majorana particles could be provided by the observation of a process called neutrinoless double beta (0νββ) decay. Neutrinoless double beta decay is a hypothesised nuclear process in which two neutrons simultaneously decay into protons with no neutrino emission. In this paper we proposed a neutrino mass model based on A4 symmetry group and studied its implications to 0νββ decay. We obtained a lower limit on |Mee| for inverted hierarchy and which can be probed in 0νββ experiments like SuperNEMO and KamLAND-Zen.

The Search for μ+ → e+γ with 10–14 Sensitivity: The Upgrade of the MEG Experiment

The MEG experiment took data at the Paul Scherrer Institute in the years 2009–2013 to test the violation of the lepton flavor conservation law, which originates from an accidental symmetry that the Standard Model of elementary particle physics has, and published the most stringent limit on the charged lepton flavor violating decay μ+→e+γ: BR(μ+→e+γ) <4.2×10−13 at 90% confidence level. The MEG detector has been upgraded in order to reach a sensitivity of 6×10−14. The basic principle of MEG II is to achieve the highest possible sensitivity using the full muon beam intensity at the Paul Scherrer Institute (7×107 muons/s) with an upgraded detector. The main improvements are better rate capability of all sub-detectors and improved resolutions while keeping the same detector concept. In this paper, we present the current status of the preparation, integration and commissioning of the MEG II detector in the recent engineering runs.

Editorial to the Special Issue “The Casimir Effect: From a Laboratory Table to the Universe”

This Special Issue presents a comprehensive picture of the Casimir effect as a multidisciplinary subject that plays an important role in diversified areas of physics ranging from quantum field theory, atomic physics and condensed matter physics to elementary particle physics, gravitation and cosmology [...]

Scalaron–Higgs inflation reloaded: Higgs-dependent scalaron mass and primordial black hole dark matter

We propose an extension of the scalaron-Higgs model by a non-minimal coupling of the Standard Model Higgs boson to the quadratic Ricci scalar resulting in a Higgs-dependent scalaron mass. The model predicts a successful stage of effective single-field Starobinsky inflation. It features a multi-field amplification mechanism leading to a peak in the inflationary power spectrum at small wavelengths which enhances the production of primordial black holes. The extended scalaron-Higgs model unifies inflationary cosmology with elementary particle physics and explains the origin of cold dark matter in terms of primordial black holes without assuming any new particles.

Quantum field theory (QFT)—built-in combinatorics

We briefly exhibit in this chapter the mathematical formalism of QFT, which actually has a non-trivial combinatorial backbone. The QFT setting can be understood as a quantum description of particles and their interactions, a description which is also compatible with Einstein's theory of special relativity. Within the framework of elementary particle physics (or high-energy physics), QFT led to the Standard Model of Elementary Particle Physics, which is the physical theory tested with the best accuracy by collider experiments. Moreover, the QFT formalism successfully applies to statistical physics, condensed matter physics and so on. We show in this chapter how Feynman graphs appear through the so-called QFT perturbative expansion, how Feynman integrals are associated to Feynman graphs and how these integrals can be expressed via the help of graph polynomials, the Kirchhoff–Symanzik polynomials. Finally, we give a glimpse of renormalization, of the Dyson–Schwinger equation and of the use of the so-called intermediate field method. This chapter mainly focuses on the so-called Phi? QFT scalar model.