How to prepare quantum states that follow classical paths

We present an alternative quantization procedure for the one-dimensional non-relativistic quantum mechanics. We show that, for the case of a free particle and a particle in a box, the complete classical and quantum correspondence can be obtained using this formulation. The resulting wave packets do not disperse and strongly peak on the classical paths. Moreover, for the case of the free particle, they satisfy minimum uncertainty relation.Comment: 10 pages, 3 figures, to appear in Europhysics Letter

Time-resolved broadband analysis of slow-light propagation and superluminal transmission of electromagnetic waves in three-dimensional photonic crystals

A time-resolved analysis of the amplitude and phase of THz pulses propagating through three-dimensional photonic crystals is presented. Single-cycle pulses of THz radiation allow measurements over a wide frequency range, spanning more than an octave below, at and above the bandgap of strongly dispersive photonic crystals. Transmission data provide evidence for slow group velocities at the photonic band edges and for superluminal transmission at frequencies in the gap. Our experimental results are in good agreement with finite-difference-time-domain simulations.Comment: 7 pages, 11 figure

Enhanced fano resonance of organic material films deposited on arrays of asymmetric split-ring resonators (A-SRRs)

Depositing very thin organic films on the surface of arrays of asymmetric split-ring resonators (A-SRRs) produces a shift in their resonance spectra that can be utilized for sensitive analyte detection. Here we show that when poly-methyl-methacrylate (PMMA) is used as an organic probe (analyte) on top of the A-SRR array, the phase and amplitude of a characteristic molecular Fano resonance associated with a carbonyl bond changes according to the spectral positions of the trapped mode resonance of the A-SRRs and their plasmonic reflection peaks. Furthermore, we localize blocks of PMMA at different locations on the A-SRR array to determine the effectiveness of detection of very small amounts of non-uniformly distributed analyte

Wigner phase space distribution as a wave function

We demonstrate that the Wigner function of a pure quantum state is a wave function in a specially tuned Dirac bra-ket formalism and argue that the Wigner function is in fact a probability amplitude for the quantum particle to be at a certain point of the classical phase space. Additionally, we establish that in the classical limit, the Wigner function transforms into a classical Koopman-von Neumann wave function rather than into a classical probability distribution. Since probability amplitude need not be positive, our findings provide an alternative outlook on the Wigner function's negativity.Comment: 6 pages and 2 figure

Enhanced hydrogenation catalyst synthesized by Desulfovibrio desulfuricans exposed to a radio frequency magnetic field

EPSRC (EP/I007806/1; EP/D05768X/1), BBSRC (BB/ C516128/1), NERC (NE/L014076/1), The Royal Society (Industrial Fellowship) and Spanish Government Sistema Nacional de Garantia Juvenil grant PEJ-2014-P-00391.This work was supported by EPSRC (grants No EP/ I007806/1 and EP/D05768X/1), BBSRC (grant No BB/ C516128/1), NERC (grant NE/L014076/1) and by a Royal Society Industrial Fellowship to LEM for secondment into C-Tech Innovation Ltd., who provided the bespoke apparatus used in this work. We acknowledge the invaluable contributions of the late Dr Ruth Wroe of C-Tech Innovation Ltd. into useful discussions and the kind permission of Drs S. Megit, C. Berry and A. Morby (University of Cardiff, UK) to show their unpublished work in Supplementary Information. This work was partially supported by the Spanish Government Sistema Nacional de Garantia Juvenil Grant PEJ-2014-P- 00391 (Promocion de Empleo Joven e Implantacion de la Garantia Juvenil 2014, MINECO) with a scholarship to JGB. We also thank the EM Centre at U. Granada for access to high-resolution electron microscopy (in Fig. S2 and S3). All authors declare no competing interests.Desulfovibrio desulfuricans reduces Pd(II) to Pd(0)-nanoparticles (Pd-NPs) which are catalytically active in 2-pentyne hydrogenation. To make Pd-NPs, resting cells are challenged with Pd(II) ions (uptake), followed by addition of electron donor to promote bioreduction of cell-bound Pd(II) to Pd(0) (bio-Pd). Application of radiofrequency (RF) radiation to prepared 5 wt% bio-Pd catalyst (60 W power, 60 min) increased the hydrogenation rate by 70% with no adverse impact on selectivity to cis-2-pentene. Such treatment of a 5 wt% Pd/carbon commercial catalyst did not affect the conversion rate but reduced the selectivity. Lower-dose RF radiation (2-8 W power, 20 min) was applied to the bacteria at various stages before and during synthesis of the bio-scaffolded Pd-NPs. The reaction rate (mu mol 2-pentyne converted s(-1)) was increased by similar to threefold by treatment during bacterial catalyst synthesis. Application of RF radiation (2 or 4 W power) to resting cells prior to Pd(II) exposure affected the catalyst made subsequently, increasing the reaction rate by 50% as compared to untreated cells, while nearly doubling selectivity for cis 2-pentene. The results are discussed with respect to published and related work which shows altered dispersion of the Pd-NPs made following or during RF exposure.UK Research & Innovation (UKRI) Engineering & Physical Sciences Research Council (EPSRC) EP/I007806/1 EP/D05768X/1UK Research & Innovation (UKRI) Biotechnology and Biological Sciences Research Council (BBSRC) BB/C516128/1UK Research & Innovation (UKRI)Natural Environment Research Council (NERC) NE/L014076/1Royal Society of London European CommissionSpanish Government Sistema Nacional de Garantia Juvenil grant PEJ-2014-P-0039

Towards Structure-Property-Function Relationships for Eumelanin

We discuss recent progress towards the establishment of important structure-property-function relationships in eumelanins - key functional bio-macromolecular systems responsible for photo-protection and immune response in humans, and implicated in the development of melanoma skin cancer. We focus on the link between eumelanin's secondary structure and optical properties such as broad band UV-visible absorption and strong non-radiative relaxation; both key features of the photo-protective function. We emphasise the insights gained through a holistic approach combining optical spectroscopy with first principles quantum chemical calculations, and advance the hypothesis that the robust functionality characteristic of eumelanin is related to extreme chemical and structural disorder at the secondary level. This inherent disorder is a low cost natural resource, and it is interesting to speculate as to whether it may play a role in other functional bio-macromolecular systems.Comment: 19 pages, 8 figures, Invited highlight article for Soft Matte

Operational Dynamic Modeling Transcending Quantum and Classical Mechanics

We introduce a general and systematic theoretical framework for Operational Dynamic Modeling (ODM) by combining a kinematic description of a model with the evolution of the dynamical average values. The kinematics includes the algebra of the observables and their defined averages. The evolution of the average values is drawn in the form of Ehrenfest-like theorems. We show that ODM is capable of encompassing wide ranging dynamics from classical non-relativistic mechanics to quantum field theory. The generality of ODM should provide a basis for formulating novel theories.Comment: 23 pages and 2 figures. Sec. VII B "Phase Space Representation in Curvilinear Coordinates" was correcte