Abstract
The aim of the paper is to describe a well-known quantum key distribution GG02 protocol using multimode coherent states generated on subcarrier frequencies of the optical spectrum. In order ...to detect signal states, we use a method of coherent detection without the participation of a local oscillator directly but where power from a carrier wave is used as such. Within the framework of the modern GG02 protocol description and the secutity proof against collective attacks, we introduce the necessary amendments to reduce our model to a model of the common system.
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•Laser-induced phase transition of GeTe thin film coating.•High optical properties contrast for two stable laser-induced phase states.•Transmissivity to reflectivity delay observed ...during reamorphisation process.•Thin film temperature kinetics’ computational model.
The article presents the results of an in-situ pump–probe study of the change’s kinetics in the optical properties of GeTe thin films associated with reversible phase transitions initiated by nanosecond laser pulses. It was shown that the change of the transmissivity and reflectivity of GeTe films in case of direct phase transition from the amorphous state to the crystalline starts at the same time, while the reverse transition is observed delay change of the transmissivity relative to the reflectivity. The value of this delay for the 100 nm GeTe thin film was estimated at t100 = 24 ns, and for the 50 nm sample – t50 = 13 ns. This time lag in changes of the transmissivity from the reflectivity in case of reamorphization films depending on sample thickness, can be explained by the high contrast of the concentration of free electrons between amorphous and crystalline states, which determine the reflectivity of the surface layer of the sample, while the transmissivity is determined by the total thickness. The experimental dependences of the kinetics of changes in the optical properties of GeTe samples under laser-induced phase transitions are in good consistent with the numerical simulation data of the Stefan problem.
We analyze the performance of quantum repeaters where the protocols of entanglement generation and swapping are based on multimode optical Schrödinger cat states produced using electro-optic ...modulation of single-mode optical cats. We employ both the mean-only approximation and exact results to calculate the distance dependencies of the mean waiting time and the repeater rate depending on the number of elementary links. The results are compared with the rates of quantum repeater schemes based on photon pairs generated via spontaneous parametric down-conversion.
In this paper, we present the approach to complete Bell state analysis based on filtering mapping. The key distinctive feature of this appoach is that it avoids complications related to using either ...hyperentanglement or representation of the Bell states as concatenated Greenber-Horne-Zeilinger (C-GHZ) state to perform discrimination procedure. We describe two techniques developed within the suggested approach and based on two-step algorithms with two different types of filtration mapping which can be called the non-demolition and semi-demolition filtrations. In the method involving non-demolition filtration measurement the filtration process employs cross-Kerr nonlinearity and the probe mode to distinguish between the two pairs of the Bell states. In the case of semi-demolition measurement, the two states are unambiguously discriminated and hence destroyed, whereas filtraton keeps the other two states intact. We show that the measurement that destroys the single photon subspace in every mode and preserves the superposition of zero and two photons can be realized with discrete photodetection based on microresonator with atoms.
Like modern microprocessors today, future processors of quantum information may be implemented using all-electrical control of silicon-based devices. A semiconductor spin qubit may be controlled ...without the use of magnetic fields by using three electrons in three tunnel-coupled quantum dots. Triple dots have previously been implemented in GaAs, but this material suffers from intrinsic nuclear magnetic noise. Reduction of this noise is possible by fabricating devices using isotopically purified silicon. We demonstrate universal coherent control of a triple-quantum-dot qubit implemented in an isotopically enhanced Si/SiGe heterostructure. Composite pulses are used to implement spin-echo type sequences, and differential charge sensing enables single-shot state readout. These experiments demonstrate sufficient control with sufficiently low noise to enable the long pulse sequences required for exchange-only two-qubit logic and randomized benchmarking.
Electron characteristics of the contributions to the mercury optical conductivity at room temperature have been calculated based on comparison of the model spectrum of the optical conductivity with ...the experimental data. It is shown that the experimental spectrum of the liquid-mercury optical conductivity can be described only taking into account the possibility of splitting the conduction band.
An exact solution of the Helmholtz equation
u
xx
+
u
yy
+
u
zz
+
k
2
u
= 0 is presented, which describes propagation of monochromatic waves in the free space. The solution has the form of a ...superposition of plane waves with a specific weight function dependent on a certain free parameter
a
. If
ka
→∞, the solution is localized in the Gaussian manner in a vicinity of a certain straight line and asymptotically coincides with the famous approximate solution known as the fundamental mode of a paraxial Gaussian beam. The asymptotics of the aforementioned exact solution does not include a backward wave.
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•The asymptotic solution for the initial condition problem of hydraulic fracture is numerically obtained.•The solution takes into account the existence of a lag between fluid and ...fracture tip.•The results show that in-situ stress plays an important role in the initial condition of hydraulic fracture.•In-situ stress being small, the distribution of fluid pressure is linear and the singularity of stress is in the tip.•In-situ stressbeing large, the slope of fluid pressure tends to infinity, no stress singularity in the tip.
The numerical asymptotic solution to the initial condition problem (early-time solution) of the pre-existing plane-strain hydraulic fracture with a fluid lag is obtained under different levels of in-situ stress. This solution can provide a more accurate initial condition for simulation of hydraulic modelling. The perturbation method is applied to calculate time-derivative terms of the governing equations based on the derivative definition, and the double-iteration method is used to seek more accurate values of these time-derivative terms. Besides, the profiles of dimensionless fracture opening and dimensionless net pressure are obtained under different levels of in-situ stress, and a simplified self-similar model with no time derivative terms is put forward, because time-derivative terms can be neglected under the large in-situ stress.
Abstract
We consider a natural generalization of the Kazantsev–Kraichnan model for a small-scale turbulent dynamo. This generalization takes into account the statistical time asymmetry of a turbulent ...flow and thus allows one to describe velocity fields with energy cascade. For three-dimensional velocity fields, a generalized Kazantsev equation is derived, and the evolution of the second-order magnetic field correlator is investigated for large but finite magnetic Prandtl numbers. It is shown that as Pr
m
→ ∞, the growth increment tends to the limit known from the T-exponential (Lagrangian deformation) method. Magnetic field generation is shown to be weaker than that in the Gaussian velocity field for any direction of the energy cascade and essentially depends on the Prandtl number.
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