687 research outputs found
Quantum gates between capacitively coupled double quantum dot two-spin qubits
We study the two-qubit controlled-not gate operating on qubits encoded in the
spin state of a pair of electrons in a double quantum dot. We assume that the
electrons can tunnel between the two quantum dots encoding a single qubit,
while tunneling between the quantum dots that belong to different qubits is
forbidden. Therefore, the two qubits interact exclusively through the direct
Coulomb repulsion of the electrons. We find that entangling two-qubit gates can
be performed by the electrical biasing of quantum dots and/or tuning of the
tunneling matrix elements between the quantum dots within the qubits. The
entangling interaction can be controlled by tuning the bias through the
resonance between the singly-occupied and doubly-occupied singlet ground states
of a double quantum dot.Comment: 12 pages, 7 figure
Exchange-based CNOT gates for singlet-triplet qubits with spin orbit interaction
We propose a scheme for implementing the CNOT gate over qubits encoded in a
pair of electron spins in a double quantum dot. The scheme is based on exchange
and spin orbit interactions and on local gradients in Zeeman fields. We find
that the optimal device geometry for this implementation involves effective
magnetic fields that are parallel to the symmetry axis of the spin orbit
interaction. We show that the switching times for the CNOT gate can be as fast
as a few nanoseconds for realistic parameter values in GaAs semiconductors.
Guided by recent advances in surface codes, we also consider the perpendicular
geometry. In this case, leakage errors due to spin orbit interaction occur but
can be suppressed in strong magnetic fields
Development of fruit diseases of microbial origin during storage at treatment with antioxidant compositions
Встановлено, що досліджувані антиоксидантні композиції пригнічували розвиток епіфітних мікроорганізмів на поверхні плодів протягом зберігання. Було зафіксовано підвищення їх стрес-толерантності. Результати експерименту доводять зменшення рівня щодобових втрат від мікробіологічних захворювань у 2…3,5 разів. Найбільший позитивний ефект при зберіганні усіх видів плодів
був отриманий при обробці композицією на основі дистинолу і лецитину
Interaction of Biliverdin Chromophore with Near-Infrared Fluorescent Protein BphP1-FP Engineered from Bacterial Phytochrome
Near-infrared (NIR) fluorescent proteins (FPs) designed from PAS (Per-ARNT-Sim repeats) and GAF (cGMP phosphodiesterase/adenylate cyclase/FhlA transcriptional activator) domains of bacterial phytochromes covalently bind biliverdin (BV) chromophore via one or two Cys residues. We studied BV interaction with a series of NIR FP variants derived from the recently reported BphP1-FP protein. The latter was engineered from a bacterial phytochrome RpBphP1, and has two reactive Cys residues (Cys15 in the PAS domain and Cys256 in the GAF domain), whereas its mutants contain single Cys residues either in the PAS domain or in the GAF domain, or no Cys residues. We characterized BphP1-FP and its mutants biochemically and spectroscopically in the absence and in the presence of denaturant. We found that all BphP1-FP variants are monomers. We revealed that spectral properties of the BphP1-FP variants containing either Cys15 or Cys256, or both, are determined by the covalently bound BV chromophore only. Consequently, this suggests an involvement of the inter-monomeric allosteric effects in the BV interaction with monomers in dimeric NIR FPs, such as iRFPs. Likely, insertion of the Cys15 residue, in addition to the Cys256 residue, in dimeric NIR FPs influences BV binding by promoting the BV chromophore covalent cross-linking to both PAS and GAF domains.Peer reviewe
Temporal Correlations of Local Network Losses
We introduce a continuum model describing data losses in a single node of a
packet-switched network (like the Internet) which preserves the discrete nature
of the data loss process. {\em By construction}, the model has critical
behavior with a sharp transition from exponentially small to finite losses with
increasing data arrival rate. We show that such a model exhibits strong
fluctuations in the loss rate at the critical point and non-Markovian power-law
correlations in time, in spite of the Markovian character of the data arrival
process. The continuum model allows for rather general incoming data packet
distributions and can be naturally generalized to consider the buffer server
idleness statistics
Universal Quantum Computation through Control of Spin-Orbit Coupling
We propose a method for quantum computation which uses control of spin-orbit
coupling in a linear array of single electron quantum dots. Quantum gates are
carried out by pulsing the exchange interaction between neighboring electron
spins, including the anisotropic corrections due to spin-orbit coupling.
Control over these corrections, even if limited, is sufficient for universal
quantum computation over qubits encoded into pairs of electron spins. The
number of voltage pulses required to carry out either single qubit rotations or
controlled-Not gates scales as the inverse of a dimensionless measure of the
degree of control of spin-orbit coupling.Comment: 4 pages, 3 figures (minor revision, references added
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