251 research outputs found
Real time reconstruction of the fast electron spectrum from high intensity laser plasma interaction using gamma counting technique
X-ray and gamma fluxes from the high intensity laser-plasma interaction are
extremely short, well beyond temporal resolution of any detectors. If laser
pulses come repetitively, the single photon counting technique allows to
accumulate the photon spectra, however, its relation to the spectrum of the
initial fast electron population in plasma is not straightforward. We present
efficient and fast approach based on the Geant4 package that significantly
reduces computer time needed to re-construct the high energy tail of electron
spectrum from experimental data accounting for the pileup effect. Here, we
first tabulate gamma spectrum from monoenergetic electron bunches of different
energy for a given experimental setup, and then compose the simulated spectrum.
To account for the pileups, we derive analytical formula to reverse the data.
We also consider errors coming from the approximation of the initial electron
spectrum by the sum of monoenergetic impacts, the finite range of the electron
spectrum, etc. and give estimates on how to choose modelling parameters to
minimize the approximation errors. Finally, we present an example of the
experimental data treatment for the case of laser-solid interaction using 50 fs
laser pulse with intensity above 1018 W/cm2.Comment: 25 pages, 10 figure
Quantum electrodynamics and photon-assisted tunnelling in long Josephson junctions
We describe the interaction between an electromagnetic field and a long
Josephson junction (JJ) driven by a dc current. We calculate the amplitudes of
emission and absorption of light via the creation and annihilation of quantized
Josephson plasma waves (JPWs). Both, the energies of JPW quanta and the
amplitudes of light absorption and emission, strongly depend on the junction's
length and can be tuned by an applied dc current. Moreover, photon-assisted
macroscopic quantum tunnelling in long Josephson junctions show resonances when
the frequency of the outside radiation coincides with the current-driven
eigenfrequencies of the quantized JPWs.Comment: 9 pages, 4 figure
Quantum metamaterial without local control
A quantum metamaterial can be implemented as a quantum coherent 1D array of
qubits placed in a transmission line. The properties of quantum metamaterials
are determined by the local quantum state of the system. Here we show that a
spatially-periodic quantum state of such a system can be realized without
direct control of the constituent qubits, by their interaction with the
initializing ("priming") pulses sent through the system in opposite directions.
The properties of the resulting quantum photonic crystal are determined by the
choice of the priming pulses. This proposal can be readily generalized to other
implementations of quantum metamaterials.Comment: 6 pages, 5 figure
Quasi-Superradiant Soliton State of Matter in Quantum Metamaterials
Strong interaction of a system of quantum emitters (e.g., two-level atoms)
with electromagnetic field induces specific correlations in the system
accompanied by a drastic insrease of emitted radiation (superradiation or
superfluorescence). Despite the fact that since its prediction this phenomenon
was subject to a vigorous experimental and theoretical research, there remain
open question, in particular, concerning the possibility of a first order phase
transition to the superradiant state from the vacuum state. In systems of
natural and charge-based artificial atome this transition is prohibited by
"no-go" theorems. Here we demonstrate numerically a similar transition in a
one-dimensional quantum metamaterial - a chain of artificial atoms (qubits)
strongly interacting with classical electromagnetic fields in a transmission
line. The system switches from vacuum state with zero classical electromagnetic
fields and all qubits being in the ground state to the quasi-superradiant (QS)
phase with one or several magnetic solitons and finite average occupation of
qubit excited states along the transmission line. A quantum metamaterial in the
QS phase circumvents the "no-go" restrictions by considerably decreasing its
total energy relative to the vacuum state by exciting nonlinear electromagnetic
solitons with many nonlinearly coupled electromagnetic modes in the presence of
external magnetic field.Comment: 6 pages, 4 figure
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