111 research outputs found
On the structure of non-full-rank perfect codes
The Krotov combining construction of perfect 1-error-correcting binary codes
from 2000 and a theorem of Heden saying that every non-full-rank perfect
1-error-correcting binary code can be constructed by this combining
construction is generalized to the -ary case. Simply, every non-full-rank
perfect code is the union of a well-defined family of -components
, where belongs to an "outer" perfect code , and these
components are at distance three from each other. Components from distinct
codes can thus freely be combined to obtain new perfect codes. The Phelps
general product construction of perfect binary code from 1984 is generalized to
obtain -components, and new lower bounds on the number of perfect
1-error-correcting -ary codes are presented.Comment: 8 page
A smoothing monotonic convergent optimal control algorithm for NMR pulse sequence design
The past decade has demonstrated increasing interests in using optimal
control based methods within coherent quantum controllable systems. The
versatility of such methods has been demonstrated with particular elegance
within nuclear magnetic resonance (NMR) where natural separation between
coherent and dissipative spin dynamics processes has enabled coherent quantum
control over long periods of time to shape the experiment to almost ideal
adoption to the spin system and external manipulations. This has led to new
design principles as well as powerful new experimental methods within magnetic
resonance imaging, liquid-state and solid-state NMR spectroscopy. For this
development to continue and expand, it is crucially important to constantly
improve the underlying numerical algorithms to provide numerical solutions
which are optimally compatible with implementation on current instrumentation
and at same time are numerically stable and offer fast monotonic convergence
towards the target. Addressing such aims, we here present a smoothing
monotonically convergent algorithm for pulse sequence design in magnetic
resonance which with improved optimization stability lead to smooth pulse
sequence easier to implement experimentally and potentially understand within
the analytical framework of modern NMR spectroscopy
Effective low-energy theory for correlated carbon nanotubes
The low-energy theory for single-wall carbon nanotubes including Coulomb
interactions is derived and analyzed. It describes two fermion chains without
interchain hopping but coupled in a specific way by the interaction. The
strong-coupling properties are studied by bosonization, and consequences for
experiments on single armchair nanotubes are discussed.Comment: 5 pages REVTeX, includes one figur
High Fidelity Quantum Gates in the Presence of Dispersion
We numerically demonstrate the control of motional degrees of freedom of an
ensemble of neutral atoms in an optical lattice with a shallow trapping
potential. Taking into account the range of quasimomenta across different
Brillouin zones results in an ensemble whose members effectively have
inhomogeneous control fields as well as spectrally distinct control
Hamiltonians. We present an ensemble-averaged optimal control technique that
yields high fidelity control pulses, irrespective of quasimomentum, with
average fidelities above 98%. The resulting controls show a broadband spectrum
with gate times in the order of several free oscillations to optimize gates
with up to 13.2% dispersion in the energies from the band structure. This can
be seen as a model system for the prospects of robust quantum control. This
result explores the limits of discretizing a continuous ensemble for control
theory
Low Energy Properties of the (n,n) Carbon Nanotubes
According to band theory, an ideal undoped (n,n) carbon nanotube is metallic.
We show that the electron-electron interaction causes it to become Mott
insulating with a spin gap. More interestingly, upon doping it develops
superconducting fluctuations.Comment: 5pages, 2eps figures, one reference added, final version, accepted to
PR
Colloquium: Trapped ions as quantum bits -- essential numerical tools
Trapped, laser-cooled atoms and ions are quantum systems which can be
experimentally controlled with an as yet unmatched degree of precision. Due to
the control of the motion and the internal degrees of freedom, these quantum
systems can be adequately described by a well known Hamiltonian. In this
colloquium, we present powerful numerical tools for the optimization of the
external control of the motional and internal states of trapped neutral atoms,
explicitly applied to the case of trapped laser-cooled ions in a segmented
ion-trap. We then delve into solving inverse problems, when optimizing trapping
potentials for ions. Our presentation is complemented by a quantum mechanical
treatment of the wavepacket dynamics of a trapped ion. Efficient numerical
solvers for both time-independent and time-dependent problems are provided.
Shaping the motional wavefunctions and optimizing a quantum gate is realized by
the application of quantum optimal control techniques. The numerical methods
presented can also be used to gain an intuitive understanding of quantum
experiments with trapped ions by performing virtual simulated experiments on a
personal computer. Code and executables are supplied as supplementary online
material (http://kilian-singer.de/ent).Comment: accepted for publication in Review of Modern Physics 201
В поисках Атлантиды: предиктивные биомаркеры ответа на иммунотерапию
The emergence and continuous development of immune checkpoint inhibitors (ICIs) therapy brings a revolution in cancer therapy history including urothelial carcinoma. Early accurate targeting and adequate treatment are critical to patient prognosis and overall survival. To overcome these limitations, two strategies are actively being pursued: identification of predictive biomarkers for clinical response to ICIs and multi-pronged combination therapies. Biomarkers might allow clinicians to practice a precision medicine approach in ICIs (biomarkerbased patient selection). The development of predictive biomarkers is needed to optimize patient benefit, minimize risk of toxicities, and guide combination approaches.The greatest focus in clinical trials and reviews has been on tumor-cell PD-L1 expression. Although PD-L1 positivity enriches for populations with clinical benefit, PD-L1 testing alone is insufficient for patient selection in most malignancies. In this review, we discuss the status of PD-L1 testing and explore emerging data on new biomarker strategies with tumor-infiltrating lymphocytes, mutational burden, immune gene signatures, microsatellite instability and molecular subtypes.Появление и постоянное развитие терапии с использованием ингибиторов иммунных контрольных точек (ICI) совершили революцию в истории лечения рака, в том числе уротелиальной карциномы. Ранний точный подбор мишени и адекватное лечение имеют решающее значение для прогноза заболевания и продолжительности общей выживаемости. Для преодоления этих ограничений активно используются 2 стратегии: идентификация прогностических биомаркеров для клинического ответа при ICI-терапии и пролонгированная комбинированная терапия. Биомаркеры могут позволить клиницистам практиковать подходы прецизионной медицины при назначении ICI-терапии (отбор пациентов на основе биомаркеров).Наибольшее внимание в клинических испытаниях и обзорах уделяется экспрессии PD-L1 в опухолевых клетках. Несмотря на то что случаи уротелиального рака с положительной экспрессией PD-L1 могут иметь потенциальную выгоду при назначении иммунотерапии, одного тестирования PD-L1 недостаточно для отбора пациентов при большинстве злокачественных новообразований. В данном обзоре мы обсуждаем статус тестирования PD-L1 и представляем новые данные о потенциальных предиктивных биомаркерах при назначении ICI-терапии: факторы противоопухолевого иммунитета, мутационную нагрузку и сигнатуры генов, микросателлитную нестабильность и молекулярные подтипы рака мочевого пузыря
Supersymmetry in carbon nanotubes in a transverse magnetic field
Electron properties of Carbon nanotubes in a transverse magnetic field are
studied using a model of a massless Dirac particle on a cylinder. The problem
possesses supersymmetry which protects low energy states and ensures stability
of the metallic behavior in arbitrarily large fields. In metallic tubes we find
suppression of the Fermi velocity at half-filling and enhancement of the
density of states. In semiconducting tubes the energy gap is suppressed. These
features qualitatively persist (although to a smaller degree) in the presence
of electron interactions. The possibilities of experimental observation of
these effects are discussed.Comment: A new section on electron interaction effects added and explanation
on roles of supersymmetry expanded. Revtex4, 6 EPS figure file
Quantum spin field effect transistor
We propose, theoretically, a new type of quantum field effect transistor that
operates purely on the flow of spin current in the absence of charge current.
This spin field effect transistor (SFET) is constructed without any magnetic
material, but with the help of spin flip mechanism provided by a rotating
external magnetic field of uniform strength. The SFET generates a constant
instantaneous spin current that is sensitively controllable by a gate voltage
as well as by the frequency and strength of the rotating field. The
characteristics of a Carbon nanotube based SFET is provided as an example
ДЕСМОИДНАЯ ОПУХОЛЬ СРЕДОСТЕНИЯ: 6-ЛЕТНЕЕ КЛИНИЧЕСКОЕ НАБЛЮДЕНИЕ ПОСЛЕ КОМБИНИРОВАННОГО ЛЕЧЕНИЯ (СЛУЧАЙ ИЗ ПРАКТИКИ)
Extra-abdominal desmoids are tumors with borderline biologic behavior and tendency to frequent local recurrence. The paper presents a case of successful treatment of this rare tumor with involvement of mediastinal structures. The combined modality treatment resulted in 6-year disease-free survival.Экстраабдоминальный десмоид – новообразование с пограничной биологической природой и склонностью к частому местному рецидивированию. Представлен случай успешного лечения редкой локализации этой опухоли с поражением структур средостения. Длительный безрецидивный период (в течение 6 лет) после лечения обусловлен применением методов комбинированного лечения.
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