Current physics research articles

A computer model of classical rolling friction. Rattlebacks for the rest of us.

The delicate dance of orbital rendezvous. Editor's Picks. Oct 18 Finite and half-infinite solenoids and the Aharonov-Bohm effect. Conservation laws and energy transformations in a class of common physics problems. Aug 19 Determination of aerodynamic drag coefficients using a drop test with a wireless accelerometer and its application to model rockets.


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Jul 18 Three-line derivation of the Thomas precession. Most Read. Jan 18 Dec 19 Coefficient of rolling friction - Lab experiment. Sep 18 The transit of Mercury: November 11, It illustrates key features of quantum mechanics: interference and the particle-wave duality of matter. In , Richard Feynman presented a thought experiment to show these features.

Here we demonstrate the full realization of his famous thought experiment. By placing a movable mask in front of a double-slit to control the transmission through the individual slits, probability distributions for single- and double-slit arrangements were observed.

Journal of Experimental and Theoretical Physics

Also, by recording single electron detection events diffracting through a double-slit, a diffraction pattern was built up from individual events. The conical shape of a shuttlecock allows it to flip on impact. As a light and extended particle, it flies with a pure drag trajectory.

We first study the flip phenomenon and the dynamics of the flight and then discuss the implications on the game. Lastly, a possible classification of different shots is proposed. Many quantum algorithms have daunting resource requirements when compared to what is available today. In this work we extend the general theory of this algorithm and suggest algorithmic improvements for practical implementations.

Specifically, we develop a variational adiabatic ansatz and explore unitary coupled cluster where we establish a connection from second order unitary coupled cluster to universal gate sets through a relaxation of exponential operator splitting. We introduce the concept of quantum variational error suppression that allows some errors to be suppressed naturally in this algorithm on a pre-threshold quantum device. Additionally, we analyze truncation and correlated sampling in Hamiltonian averaging as ways to reduce the cost of this procedure. Finally, we show how the use of modern derivative free optimization techniques can offer dramatic computational savings of up to three orders of magnitude over previously used optimization techniques.

The field comprises four domains: quantum communication, where individual or entangled photons are used to transmit data in a provably secure way; quantum simulation, where well-controlled quantum systems are used to reproduce the behaviour of other, less accessible quantum systems; quantum computation, which employs quantum effects to dramatically speed up certain calculations, such as number factoring; and quantum sensing and metrology, where the high sensitivity of coherent quantum systems to external perturbations is exploited to enhance the performance of measurements of physical quantities.

This article presents an updated summary of this roadmap. We propose and analyse a simple method to measure simultaneously the real and imaginary parts of the effective refractive index of a turbid suspension of particles. The method is based on measurements of the angle of refraction and transmittance of a laser beam that traverses a hollow glass prism filled with a colloidal suspension. We provide a comprehensive assessment of the method.

It can offer high sensitivity while still being simple to interpret. We present results of experiments using an optically turbid suspension of polystyrene particles and compare them with theoretical predictions.


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  • We also report experimental evidence showing that the refractive behaviour of the diffuse component of light coming from a suspension depends on the volume fraction of the colloidal particles. It has recently been shown that in every spatial dimension there exist precisely five distinct classes of topological insulators or superconductors. Within a given class, the different topological sectors can be distinguished, depending on the case, by a or a topological invariant.

    This is an exhaustive classification. Here we construct representatives of topological insulators and superconductors for all five classes and in arbitrary spatial dimension d , in terms of Dirac Hamiltonians.

    Go from Quantum to Cosmic

    Using these representatives we demonstrate how topological insulators superconductors in different dimensions and different classes can be related via 'dimensional reduction' by compactifying one or more spatial dimensions in 'Kaluza—Klein'-like fashion. For -topological insulators superconductors this proceeds by descending by one dimension at a time into a different class. The -topological insulators superconductors , on the other hand, are shown to be lower-dimensional descendants of parent -topological insulators in the same class, from which they inherit their topological properties.

    Furthermore, we derive for general spatial dimensions a relation between the topological invariant that characterizes topological insulators and superconductors with chiral symmetry i. Finally, we also discuss topological field theories describing the spacetime theory of linear responses in topological insulators superconductors and study how the presence of inversion symmetry modifies the classification of topological insulators superconductors.

    The monochromatic Dirac and polychromatic Titulaer—Glauber quantized field theories QFTs of electromagnetism are derived from a photon-energy wave function in much the same way that one derives QFT for electrons, i. The photon wave function and its equation of motion are established from the Einstein energy—momentum—mass relation, assuming a local energy density.

    Research in Physics

    This yields a theory of photon wave mechanics PWM. The proper Lorentz-invariant single-photon scalar product is found to be non-local in coordinate space, and is shown to correspond to orthogonalization of the Titulaer—Glauber wave-packet modes. The wave functions of PWM and mode functions of QFT are shown to be equivalent, evolving via identical equations of motion, and completely describe photonic states. The second-order coherence tensors of classical coherence theory and the two-photon wave functions are shown to propagate equivalently. We propose a practical mode converter based on spectral filtering to convert between wave packets and their corresponding biorthogonal dual wave packets.

    To achieve universal quantum computation via general fault-tolerant schemes, stabilizer operations must be supplemented with other non-stabilizer quantum resources. For qudit quantum computing with odd dimension d , it is known that quantum states with non-negative Wigner function can be efficiently simulated classically. First, inspired by this observation, we introduce a resource theory based on completely positive-Wigner-preserving quantum operations as free operations, and we show that they can be efficiently simulated via a classical algorithm.

    Second, we introduce two efficiently computable magic measures for quantum channels, called the mana and thauma of a quantum channel. As applications, we show that these measures not only provide fundamental limits on the distillable magic of quantum channels, but they also lead to lower bounds for the task of synthesizing non-Clifford gates. Third, we propose a classical algorithm for simulating noisy quantum circuits, whose sample complexity can be quantified by the mana of a quantum channel.

    We further show that this algorithm can outperform another approach for simulating noisy quantum circuits, based on channel robustness. Finally, we explore the threshold of non-stabilizerness for basic quantum circuits under depolarizing noise. We study two-dimensional 2D matter-wave solitons in spinor Bose—Einstein condensates under the action of the spin—orbit coupling and opposite signs of the self- and cross-interactions. Stable 2D two-component solitons of the mixed-mode type are found if the cross-interaction between the components is attractive, while the self-interaction is repulsive in each component.

    Stable solitons of the semi-vortex type are formed in the opposite case, under the action of competing self-attraction and cross-repulsion.

    Current Applied Physics

    The solitons exist with the total norm taking values below a collapse threshold. Further, in the case of the repulsive self-interaction and inter-component attraction, stable 2D self-trapped modes, which may be considered as quantum droplets QDs , are created if the beyond-mean-field Lee—Huang—Yang terms are added to the self-repulsion in the underlying system of coupled Gross—Pitaevskii equations. Stable QDs of the mixed-mode type, of a large size with an anisotropic density profile, exist with arbitrarily large values of the norm, as the Lee—Huang—Yang terms eliminate the collapse.

    The effect of the spin—orbit coupling term on characteristics of the QDs is systematically studied. We also address the existence and stability of QDs in the case of SOC with mixed Rashba and Dresselhaus terms, which makes the density profile of the QD more isotropic. Thus, QDs in the spin-orbit-coupled binary Bose—Einstein condensate are for the first time studied in the present work. We examine the momentum and angular momentum AM properties of monochromatic optical fields in dispersive and inhomogeneous isotropic media, using the Abraham- and Minkowski-type approaches, as well as the kinetic Poynting-like and canonical with separate spin and orbital degrees of freedom pictures.

    While the kinetic Abraham—Poynting momentum describes the energy flux and the group velocity of the wave, the Minkowski-type quantities, with proper dispersion corrections, describe the actual momentum and AM carried by the wave. The kinetic Minkowski-type momentum and AM densities agree with phenomenological results derived by Philbin.

    Using the canonical spin—orbital decomposition, previously used for free-space fields, we find the corresponding canonical momentum, spin and orbital AM of light in a dispersive inhomogeneous medium. These acquire a very natural form analogous to the Brillouin energy density and are valid for arbitrary structured fields.

    The general theory is applied to a non-trivial example of a surface plasmon-polariton SPP wave at a metal-vacuum interface. We show that the integral momentum of the SPP per particle corresponds to the SPP wave vector, and hence exceeds the momentum of a photon in the vacuum.

    While the intrinsic orbital AM vanishes, the transverse spin can change its sign depending on the SPP frequency. Importantly, we present both macroscopic and microscopic calculations, thereby proving the validity of the general phenomenological results. The microscopic theory also predicts a transverse magnetization in the metal i. Biologically functional liquid—liquid phase separation of intrinsically disordered proteins IDPs is driven by interactions encoded by their amino acid sequences. Little is currently known about the molecular recognition mechanisms for distributing different IDP sequences into various cellular membraneless compartments.

    International Journal of Physics and Astronomy (IJPA)

    Pertinent physics was addressed recently by applying random-phase-approximation RPA polymer theory to electrostatics, which is a major energetic component governing IDP phase properties. To make progress toward deciphering the phase behaviors of multiple IDP sequences, the RPA formulation for one IDP species plus solvent is hereby extended to treat polyampholyte solutions containing two IDP species plus solvent. The new formulation generally allows for binary coexistence of two phases, each containing a different set of volume fractions for the two different IDP sequences.

    The asymmetry between the two predicted coexisting phases with regard to their ratios for the two sequences increases with increasing mismatch between their charge patterns. An intuitive illustration of this trend is provided by FH models, whereby a hypothetical case of ternary coexistence is also explored. Augmentations of the present RPA theory with a relative permittivity that depends on IDP volume fraction lead to higher propensities to phase separate, in line with the case with one IDP species we studied previously.

    Notably, the cooperative, phase-separation-enhancing effects predicted by the prescriptions for we deem physically plausible are much more prominent than that entailed by common effective medium approximations based on Maxwell Garnett and Bruggeman mixing formulas. Ramifications of our findings on further theoretical development for IDP phase separation are discussed.

    We theoretically investigate the propagation of heat currents in a three-terminal quantum dot engine. Electron—electron interactions introduce state-dependent processes which can be resolved by energy-dependent tunneling rates.


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    • Pramana – Journal of Physics | Indian Academy of Sciences.
    • We identify the relevant transitions which define the operation of the system as a thermal transistor or a thermal diode. In the former case, thermal-induced charge fluctuations in the gate dot modify the thermal currents in the conductor with suppressed heat injection, resulting in huge amplification factors and the possible gating with arbitrarily low energy cost. In the latter case, enhanced correlations of the state-selective tunneling transitions redistribute heat flows giving high rectification coefficients and the unexpected cooling of one conductor terminal by heating the other one.

      Undergraduate Research Papers

      We propose quantum dot arrays as a possible way to achieve the extreme tunneling asymmetries required for the different operations. In iron-based superconductors the interactions driving the nematic order that breaks the lattice four-fold rotational symmetry in the iron plane may also facilitate the Cooper pairing, but experimental determination of these interactions is challenging because the temperatures of the nematic order and the order of other electronic phases appear to match each other or to be close to each other.

      Here we performed field-dependent 77 Se-nuclear magnetic resonance NMR measurements on single crystals of iron-based superconductor FeSe, with magnetic field B 0 up to 16 T.