Signatures Of Quantum Effects Research Articles

Gravitationally induced entanglement dynamics between two quantum walkers

Quantum walk is a synonym for multi-path interference and faster spread of a particle in a superposition of position space. We study the effects of a quantum mechanical interaction modeled to mimic quantum mechanical gravitational interaction between the two states of the walkers. The study has been carried out to investigate the entanglement generation between the two quantum walkers that do not otherwise interact. We see that the states do in fact get entangled more and more as the quantum walks unfold, and there is an interesting dependence of entanglement generation on the mass of the two particles performing the walks. With the introduction of noise into the dynamics, we also show the sensitivity of entanglement between the two walkers on the noise introduced in one of the walks. The signature of quantum effects due to gravitational interactions highlights the potential role of quantum systems in probing the nature of gravity.

Signatures of quantum effects on radiation reaction in laser–electron-beam collisions

Two signatures of quantum effects on radiation reaction in the collision of a ${\sim}$GeV electron beam with a high intensity (${>}3\times 10^{20}~\text{W}~\text{cm}^{-2}$) laser pulse have been considered. We show that the decrease in the average energy of the electron beam may be used to measure the Gaunt factor $g$ for synchrotron emission. We derive an equation for the evolution of the variance in the energy of the electron beam in the quantum regime, i.e. quantum efficiency parameter $\unicode[STIX]{x1D702}\not \ll 1$. We show that the evolution of the variance may be used as a direct measure of the quantum stochasticity of the radiation reaction and determine the parameter regime where this is observable. For example, stochastic emission results in a 25 % increase in the standard deviation of the energy spectrum of a GeV electron beam, 1 fs after it collides with a laser pulse of intensity $10^{21}~\text{W}~\text{cm}^{-2}$. This effect should therefore be measurable using current high-intensity laser systems.

Jahn-Teller versus quantum effects in the spin-orbital materialLuVO3

We report on combined neutron and resonant x-ray scattering results, identifying the nature of the spin-orbital ground state and magnetic excitations in LuVO3 as driven by the orbital parameter. In particular, we distinguish between models based on orbital Peierls dimerization, taken as a signature of quantum effects in orbitals, and Jahn-Teller distortions, in favor of the latter. In order to solve this long-standing puzzle, polarized neutron beams were employed as a prerequisite in order to solve details of the magnetic structure, which allowed quantitative intensity-analysis of extended magnetic excitation data sets. The results of this detailed study enabled us to draw definite conclusions about classical vs quantum behavior of orbitals in this system and to discard the previous claims about quantum effects dominating the orbital physics of LuVO3 and similar systems.

Quantum effects in the transport properties of nanoelectronic three-terminal Y-junction devices

We report on a theoretical study of the electrical properties of three-terminal ballistic junction (TBJ) devices, consisting of three perfect leads and a ballistic coupling region, using a multiterminal scattering-matrix approach and the Landauer-B\"uttiker transport theory. The calculations have been performed for TBJ devices with different structure properties, at both high and low temperatures, as well as at both small and large applied bias voltages. The study is focused on the effects of quantum scattering, which is treated by exact numerical calculations. It is shown that when operated in the push-pull fashion, i.e., by applying finite voltages ${V}_{l}=V$ and ${V}_{r}=\ensuremath{-}V$ to the left and right branches, the TBJ devices exhibit strong nonlinearities in the output voltage ${V}_{c}$ calculated at the central branch. At high temperatures, the output voltage ${V}_{c}$ as a function of V shows the same nonlinear characteristics as observed in recent theoretical analyses and experimental measurements. These high-temperature electrical characteristics are found to be qualitatively insensitive to the structure details of the devices and reveal little effect of quantum scattering. At low temperatures, the output voltage ${V}_{c}$ shows fluctuations, and can assume either negative or positive values, depending on the chemical potential, at small bias regions. These behaviors are explained in terms of the fluctuations seen in the transmissions between the terminals, while the transmission fluctuations are shown to arise from strong scattering by quasibound states formed in the junction cavity region and are therefore signatures of quantum effects. Based on the quantum fluctuation nature of the device characteristics, a single multilogic device, constructed with a single TBJ, with switching of the logic functions by means of a gate, is proposed.