No qualms about quantum theory (Vol. 45 No. 1)

‘Schrödinger’s cat state associated with an imagined superposition of a dead and live cat has no reality.’

The alleged shortcomings of quantum theory do not hold up to scrutiny. A colloquium paper peers into the alleged issues associated with quantum theory. The author reviews a selection of the potential problems of the theory. He sets out to demystify a selected set of objections targeted against quantum theory in the literature. He takes the example of Schrödinger’s infamous cat. The term ‘Schrödinger’s cat state’ is routinely applied to superposition of so-called quantum states of a particle. However, this imagined superposition of a dead and live cat has no reality. Indeed, it confuses a physical object with its description. Other myths debunked in this paper include the provision of proof that quantum theory is well defined, has a clear interpretation, is a local theory, is not reversible, and does not feature any instant action at a distance. It also demonstrates that there is no measurement problem, despite the fact that the measure is commonly known to disturb the system under measurement.

B.G. Englert, ‘On Quantum Theory’, Eur. Phys. J. D, 67, 238 (2013)
[Abstract]

Noise down, neuron signals up (Vol. 43 No. 6)

Tuning factors affecting background noise could improve neuronal communication.

M. Uzuntarla, M. Ozer, and D.Q. Guo, ‘Controlling the First-Spike Latency Response of a Single Neuron via Unreliable Synaptic Transmission’, Eur. Phys. J. B, 85, 282 (2012)
[Abstract]

Noise produces volcanic seismicity, akin to a drumbeat (Vol. 46 No. 4)

A new study shows that relatively small external disturbances play a crucial role in chaotic phenomena like the recent Calbuco volcanic eruption in Chile, leading to drum-beat-like seismicity.

Volcanoes are considered chaotic systems. They are difficult to model because the geophysical and chemical parameters in volcanic eruptions exhibit high levels of uncertainty. Now, the authors have further extended an eruption model—previously developed by other scientists—to the friction force at work between the volcanic plug and volcanic conduit surface. The results provide evidence that volcanic activity can be induced by external noises that would not otherwise have been predicted by the model. The authors show that the external noise is also linked to the appearance of large-amplitude oscillations in the volcanic plug and high seismicity. An increase in noise intensity leads to drumbeat-type plug movement, exhibiting irregular periodicity dependent on noise. Such beat-type behaviour is a building block for understanding the physical mechanisms of volcanic drumbeat seismicity.

D. V. Alexandrov, I. A. Bashkirtseva and L. B. Ryashko, How a small noise generates large-amplitude oscillations in the volcanic plug and produces high seismicity, Eur. Phys. J. B 88, 106 (2015)
[Abstract]

Non-Stationary Noise with Memory in Josephson Junctions (Vol. 49, No. 3)

In addition to the non-dissipative supercurrent, Josephson junctions also possess a dissipative memristive current component, meaning that the instantaneous resistance of the junction depends on the history of the current. Devices that display this exotic behavior are currently under intense study due to possible applications ranging from fast, high-density, nonvolatile computer memories to neuromorphic computing. In a previous work, the authors suggested a novel device to isolate this current component and thus realize a superconducting memristor. In this work the manifestation of the memristive behaviour in the current noise is considered. The presence of memory renders this noise non-stationary. The authors theoretically characterize both the thermal noise and the 'dynamic'-noise arising across a biased junction, using a mixed time-frequency description. A way to detect this effect of the memristive behaviour on the current noise is also proposed, which should be feasible with current experimental tools.

F. Sheldon, S. Peotta and M. Di Ventra, Phase-dependent noise in Josephson junctions, Eur. Phys. J. Appl. Phys. 81, 10601 (2018)
[Abstract]

Nonexistence of PT-symmetric gain-loss photonic quantum systems (Vol. 49 No.5-6)

Our common understanding of quantum mechanics relies on the Hamiltonian operator describing any quantum mechanical system to be Hermitian. This has been challenged 20 years ago by the discovery that, for an operator to possess real eigenvalues, it only needs to be invariant under combined parity-time (PT) symmetry operations. This had profound impact on photonics where potential landscapes with tailored gain and loss for electromagnetic waves can easily be implemented.

However, this is as far as the analogy to quantum mechanics can be taken. A straightforward implementation of gain-loss structures for quantum states of light - even for the most classical ones, coherent states - fails. As the authors show in this article, concatenating lossy and amplifying media turn coherent states into thermally broadened quantum states, whose first moments (i.e. their amplitudes) are retained, but whose variances are increased proportional to the amount of gain.

This shows that PT-symmetric quantum optics cannot be implemented within the prevailing paradigm of using distributed gain and loss. The wider consequence of this simple result hints at the limits of simulating quantum physics beyond wave mechanics using photonic quantum systems.

S. Scheel and A. Szameit, PT-symmetric photonic quantum systems with gain and loss do not exist, EPL 122, 34001 (2018)
[Abstract]

Nonlinear scattering of atomic bright solitons in disorder (Vol. 48, No. 3)

Atomic bright solitons are self-trapping Bose-Einstein condensates. They exist in one-dimension because of attractive interactions. We observe nonlinear scattering of 39K atomic bright solitons launched in a one-dimensional disordered potential. The atoms from solitons behave collectively, i.e. are either mostly reflected or transmitted in contrast to non interacting atoms, which behave as independent quantum particles. This is the first observation of a non-linear behaviour with atomic bright solitons beyond their self-trapped nature. It requires the soliton interaction energy to be of the order of its center-of-mass kinetic energy. Our observations are reproduced in a mean-field framework by Gross-Pitaevskii simulations, while mesoscopic quantum superpositions of the soliton being fully reflected and fully transmitted are not expected for our parameters. We discuss the conditions for observing such superpositions, which would find applications in atom interferometry beyond the standard quantum limit.

A. Boissé, G. Berthet, L. Fouché, G. Salomon, A. Aspect, S. Lepoutre and T. Bourdel, Nonlinear scattering of atomic bright solitons in disorder, EPL 117, 10007 (2017)
[Abstract]

Novel beams made of twisted atoms (Vol. 44 No. 5)

'Snapshot' of atomic Bessel beam profiles.

A.G. Hayrapetyan, O. Matula, A. Surzhykov and S. Fritzsche, 'Bessel beams of two-level atoms driven by a linearly polarized laser field', Eur. Phys. J. D, 67, 167 (2013)
[Abstract]

Novel high-power microwave generator (Vol. 46 No. 3)

A new study explores the viability of a novel structure to be used as a component of a high-power microwave source, designed to transfer energy to targets via ultra-high-frequency radio waves.

High-power microwaves are frequently used in civil and military applications. In a new study the authors demonstrate that their proposed novel method, which is capable of producing such microwaves, offers a viable alternative to traditional approaches.

To generate such high-power microwaves, researchers rely on devices referred to as backward wave oscillators, which are designed to transform the energy of an intense electron beam propagating in a slow electro-dynamic structure—SWS—into electromagnetic radiation at microwave frequencies.

Metallic cylinders with a sinusoidally shaped, periodically corrugated inner wall are being extensively used as SWS. But they are difficult to manufacture. Now, the authors propose an alternative shape of the SWS, in the form of a novel semi-circular structure and prove it is a viable alternative for generating high-power microwaves.

Md. Ghulam Saber, R.Hasan Sagor and Md. Ruhul Amin, Numerical study of the dispersion characteristics of a semi-circularly corrugated slow wave structure, Eur. Phys. J. D 69, 38 (2015)
[Abstract]

Novel plasma diagnostics method (Vol. 46 No. 4)

Could the mundane action of switching on an energy saving light bulb still hold secrets? It does, at least for physicists. These bulbs are interesting because they contain low-temperature plasma—a gas containing charges from ions and electrons. Now, the authors have developed a method that could be used for measuring the increase in the plasma force on the inner side of such a light bulb when the light is switched on. These findings have implications for plasma diagnostics concerning plasma-wall interactions used in surface modification and the production of thin film solar cells and microchips. This could lead to a promising new kind of plasma diagnostics, providing insights into processes that conventional electrical probes can’t detect.

T. Trottenberg, T. Richter and H. Kersten,, Measurement of the force exerted on the surface of an object immersed in a plasma, Eur. Phys. J. D 69, 91 (2015)
[Abstract]

Novel plasma jet offshoot phenomenon explains blue atmospheric jets (Vol. 48 No. 2)

Russian physicists identify mysterious right-angle side-jet occurring off the plasma arc in air at ambient pressure conditions

Ionised matter, like plasma, still holds secrets. Physicists working with plasma jets, made of a stream of ionised matter, have just discovered a new phenomenon. Indeed, the authors found a new type of discharge phenomenon in an atmospheric pressure plasma. It has been dubbed apokamp—from the Greek words for ‘off’ and ‘bend’, because it appears at a perpendicular angle to where plasma jets bend. Their findings have been recently published and are particularly relevant for the development of novel applications in medicine, health care and materials processing because they involve air at normal atmospheric pressure, which would make it cheaper than applications in inert gases or nitrogen. This phenomenon can help explain the blue jet phenomenon identified in 1994 in the upper atmosphere, where strange upwards-facing jets develop from thunderstorm clouds.

E. А. Sosnin, V. А. Panarin, V. S. Skakun , E. Kh. Baksht and V. F. Tarasenko, Dynamics of apokamp-type atmospheric pressure plasma jets, Eur. Phys. J. D 71, 25 (2017)
[Abstract]

NSD2019 Conference Proceedings (Vol. 51, No. 1)

The fourth International Conference on Nuclear Structure and Dynamics NSD2019 was held in Venice on May 13-17, 2019. The conference belongs to a series of conferences devoted to the most recent experimental and theoretical advances in the field of nuclear structure and reactions. The focus was on topics covering most of the research areas in low energy nuclear physics: Nuclear structure and reactions far from stability, Collective phenomena and symmetries, Dynamics and thermodynamics of light and heavy nuclei, Sub and near barrier reactions, Fusion and fission dynamics, Ab-initio calculations, cluster models and shell model, Nuclear energy density functionals, Nuclear astrophysics, Fundamental interactions. Important new results were outlined in the various subfields, spanning the whole range from neutron-deficient to neutron-rich nuclei and from light to heavy ions.

G. de Angelis and L. Corradi (Eds.), IV International Conference on Nuclear Structure and Dynamics (NSD2019), Venice, Italy, May 13-17 , 2019, EPJ Web of Conferences 223 (2019), ISBN: 978-2-7598-9084-2
[Proceedings]

Nuclear and Quark Matter at High Temperature (Vol. 48, No. 4)

In high-temperature field theory applied to nuclear physics, in particular to relativistic heavy-ion collisions, it is a longstanding question how hadrons precisely transform into a quark-gluon matter and back. The change in the effective number of degrees of freedom is rather gradual than sudden, despite the identification of a single deconfinement temperature. In order to gain an insight into this issue while considering the structure of the QGP we review the spectral function approach and its main consequences for the medium properties, including the shear viscosity. The figure plots a sample spectral density on the left and the effective number of degrees of freedom (energy density relative to the free Boltzmann gas) to the right. Two thin spectral lines result in a doubled Stefan-Boltzmann limit (SB), while any finite width reduces the result down to a single SB. When spectral lines become wide, their individual contributions to energy density and pressure drops. Continuum parts have negligible contribution. This causes the melting of hadrons like butter melts in the Sun, with no latent heat in this process.

T.S.Biró, A.Jakovác and Z.Schram, : Nuclear and quark matter at high temperature, Eur. Phys. J. A 53, 52 (2017)
[Abstract]

Nuclear physics with a medium-energy Electron-Ion Collider (Vol. 43 No. 5)

Possible realizations of a medium-energy EIC: MEIC at Jefferson Lab (top) and eRHIC at Brookhaven National Lab (bottom)

A. Accardi, V. Guzey, A. Prokudin and C. Weiss, ‘Nuclear physics with a medium-energy Electron-Ion Collider’, Eur. Phys. J. A (2012) 48, 92
[Abstract]

Nuclear-structure studies of exotic nuclei with MINIBALL (Vol. 49, No. 2)

Investigations of exotic nuclei at the ISOLDE facility of CERN are pursued with reaccelerated radioactive ion beams by means of high-resolution g-ray spectroscopy. The experimental programme covers a range of topics, which are addressed with beams ranging from neutron-rich magnesium isotopes up to heavy radium isotopes. The nuclear-structure and nuclear-reaction studies provide important insights into collective properties and single particle excitations. The most important outcomes of these measurements include: discoveries of rare nuclear shapes like octupole deformation in the actinide region; the coexistence of different intrinsic nuclear shapes at low excitation energy, and within a very narrow energy range in strontium and mercury isotopes, for which nuclear shell model investigations yielded considerable discrepancies from theory when extrapolated from known stable nuclei; and the remarkable behaviour of exotic neutron-rich nuclei with the “magic” number of 20 neutrons and in the vicinity of semi-magic chains of Ni- and Sn isotopes. The article summarized results obtained with the REX-ISOLDE facility which is the precursor of the newly inaugurated HIE-ISOLDE accelerator at CERN. The new installation allows the in-beam spectroscopy programme to be continued with higher secondary-beam intensity, higher beam energy and better beam quality. The first results have been obtained after commissioning of the super-conducting accelerator.

P. A. Butler, J. Cederkall and P. Reiter, Nuclear-structure studies of exotic nuclei with MINIBALL, J. Phys. G: Nucl. Part. Phys. 44, 044012 (2017)
[Abstract]

Observation of metastable hcp solid helium (Vol. 42, No. 6)

Partial phase diagram of helium and minimum pressures achieved at different temperatures between 1.1K and 1.4K. The metastable domain is below the melting line.

Observation of metastable hcp solid helium
F. Souris, J. Grucker, J. Dupont-Roc and Ph. Jacquier, EPL, 95, 66001 (2011)
[Abstract]