1,951 research outputs found
Вероятность ошибочной регистрации данных в однофотонном канале связи стирающего типа с приёмником на основе счётчика фотонов
When measuring low-power optical signals, it is necessary to ensure the highest reliability of the received data, which is especially important for single-photon communication channels. This determines the expediency of using photon counters as receiving modules for such channels. They are highly sensitive, but are characterized by data recording errors. Therefore, the purpose of this work was to investigate the influence of the intensity of the registered optical radiation J0 during the transmission of binary symbols “0” on the probability of registering symbols “1” at the output of the communication channel in the presence of symbols “0” at its input P(1/0).The statistical distributions of the mixture of the number of dark and signal pulses at the output of the photon counter during the registration of binary symbols “0” Pst0 (N ) were determined. To do this, a technique was used to reduce information loss. As a result, the minimum probability P(1/0) was reached.The probabilities P(1/0) were calculated for a communication channel containing a photon counter as a receiving module. This calculation was carried out at different values of the supply voltage of the avalanche photodetector U and the intensity of the optical signal used to transmit the binary symbols “0” J0 .The experimental results showed that with increasing optical signal intensity J0 , the dependences P(1/0) on J0 initially remain almost unchanged and retain a constant value. However, with a further increase in J0 , there is a linearly increasing character of the dependences P(1/0) on J0 . Moreover, with other equal reception parameters, such a character of the dependences P(1/0) on J0 begins to manifest itself at higher intensities of the optical signal J0 with an increase in the supply voltage of the avalanche photodetector.При измерении маломощных оптических сигналов, передаваемых в каналах однофотонной связи, приёмные модули должны обеспечивать наибольшую достоверность принятых данных.В этой связи целесообразно использовать счётчики фотонов, которые являются высокочувствительными, однако характеризуются ошибками регистрации данных. Поэтому цель работы– исследовать влияние интенсивности регистрируемого оптического излучения J0 при передаче двоичных символов «0» на вероятность регистрации на выходе канала связи символов «1» при наличии символов «0» на его входе P(1/0).На основе методики уменьшения потерь информации определены статистические распределения смеси числа темновых и сигнальных импульсов на выходе счётчика фотонов при регистрации двоичных символов «0» Pst0 (N ), при которых вероятность P(1/0) минимальная.Определены вероятности P(1/0) для канала связи, содержащего в качестве приёмного модуля счётчик фотонов при различных значениях напряжения питания лавинного фотоприёмника Uпит и интенсивности оптического сигнала, используемого для передачи двоичных символов «0» J0 .Экспериментальные результаты показали, что с увеличением интенсивности оптического сигнала J0 зависимости P(1/0) от J0 вначале практически не изменяются и сохраняют постоянную величину. Однако при дальнейшем увеличении J0 имеет место линейно возрастающий характер зависимостей P(1/0) от J0 . Причём при прочих равных параметрах приёма такой характер зависимостей P(1/0) от J0 начинает проявляться при бо́льших интенсивностях оптического сигнала J0 с увеличением напряжения питания лавинного фотоприёмника
Second harmonic electromagnetic emission of a turbulent magnetized plasma driven by a powerful electron beam
The power of second harmonic electromagnetic emission is calculated for the
case when strong plasma turbulence is excited by a powerful electron beam in a
magnetized plasma. It is shown that the simple analytical model of strong
plasma turbulence with the assumption of a constant pump power is able to
explain experimentally observed bursts of electromagnetic radiation as a
consequence of separate collapse events. It is also found that the
electromagnetic emission power calculated for three-wave interaction processes
occurring in the long-wavelength part of turbulent spectrum is in
order-of-magnitude agreement with experimental results
Single-shot single-gate RF spin readout in silicon
For solid-state spin qubits, single-gate RF readout can help minimise the
number of gates required for scale-up to many qubits since the readout sensor
can integrate into the existing gates required to manipulate the qubits
(Veldhorst 2017, Pakkiam 2018). However, a key requirement for a scalable
quantum computer is that we must be capable of resolving the qubit state within
single-shot, that is, a single measurement (DiVincenzo 2000). Here we
demonstrate single-gate, single-shot readout of a singlet-triplet spin state in
silicon, with an average readout fidelity of at a
measurement bandwidth. We use this technique to measure a triplet to
singlet relaxation time of in precision donor quantum
dots in silicon. We also show that the use of RF readout does not impact the
maximum readout time at zero detuning limited by the to decay,
which remained at approximately . This establishes single-gate
sensing as a viable readout method for spin qubits
Probability of Erroneous Data Registration in a Single Photon Erasure-Type Communication Channel with a Receiver Based on a Photon Counter
When measuring low-power optical signals, it is necessary to ensure the highest reliability of the received data, which is especially important for single-photon communication channels. This determines the
expediency of using photon counters as receiving modules for such channels. They are highly sensitive, but
are characterized by data recording errors. Therefore, the purpose of this work was to investigate the influence
of the intensity of the registered optical radiation J0 during the transmission of binary symbols “0” on the
probability of registering symbols “1” at the output of the communication channel in the presence of symbols
“0” at its input P(1/0).
The statistical distributions of the mixture of the number of dark and signal pulses at the output of the
photon counter during the registration of binary symbols “0” Pst0 (N ) were determined. To do this, a technique was used to reduce information loss. As a result, the minimum probability P(1/0) was reached.
The probabilities P(1/0) were calculated for a communication channel containing a photon counter as a
receiving module. This calculation was carried out at different values of the supply voltage of the avalanche
photodetector U and the intensity of the optical signal used to transmit the binary symbols “0” J0 .
The experimental results showed that with increasing optical signal intensity J0 , the dependences P(1/0)
on J0 initially remain almost unchanged and retain a constant value. However, with a further increase in J0 ,
there is a linearly increasing character of the dependences P(1/0) on J0 . Moreover, with other equal reception
parameters, such a character of the dependences P(1/0) on J0 begins to manifest itself at higher intensities of
the optical signal J0 with an increase in the supply voltage of the avalanche photodetector
Inhomogeneous Quasi-stationary States in a Mean-field Model with Repulsive Cosine Interactions
The system of N particles moving on a circle and interacting via a global
repulsive cosine interaction is well known to display spatially inhomogeneous
structures of extraordinary stability starting from certain low energy initial
conditions. The object of this paper is to show in a detailed manner how these
structures arise and to explain their stability. By a convenient canonical
transformation we rewrite the Hamiltonian in such a way that fast and slow
variables are singled out and the canonical coordinates of a collective mode
are naturally introduced. If, initially, enough energy is put in this mode, its
decay can be extremely slow. However, both analytical arguments and numerical
simulations suggest that these structures eventually decay to the spatially
uniform equilibrium state, although this can happen on impressively long time
scales. Finally, we heuristically introduce a one-particle time dependent
Hamiltonian that well reproduces most of the observed phenomenology.Comment: to be published in J. Phys.
Recombination limited energy relaxation in a BCS superconductor
We study quasiparticle energy relaxation at sub-kelvin temperatures by
injecting hot electrons into an aluminium island and measuring the energy flux
from electrons into phonons both in the superconducting and in the normal
state. The data show strong reduction of the flux at low temperatures in the
superconducting state, in qualitative agreement with the presented
quasiclassical theory for clean superconductors. Quantitatively, the energy
flux exceeds that from the theory both in the superconducting and in the normal
state, possibly suggesting an enhanced or additional relaxation process
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