1,361 research outputs found
Quantum Decoherence with Holography
Quantum decoherence is the loss of a system's purity due to its interaction
with the surrounding environment. Via the AdS/CFT correspondence, we study how
a system decoheres when its environment is a strongly-coupled theory. In the
Feynman-Vernon formalism, we compute the influence functional holographically
by relating it to the generating function of Schwinger-Keldysh propagators and
thereby obtain the dynamics of the system's density matrix.
We present two exactly solvable examples: (1) a straight string in a BTZ
black hole and (2) a scalar probe in AdS. We prepare an initial state that
mimics Schr\"odinger's cat and identify different stages of its decoherence
process using the time-scaling behaviors of R\'enyi entropy. We also relate
decoherence to local quantum quenches, and by comparing the time evolution
behaviors of the Wigner function and R\'enyi entropy we demonstrate that the
relaxation of local quantum excitations leads to the collapse of its
wave-function.Comment: 55 pages, 13 figures; v2 47 pages & 13 figs, minor revision to match
published versio
Tailoring excitonic states of van der Waals bilayers through stacking configuration, band alignment and valley-spin
Excitons in monolayer semiconductors have large optical transition dipole for
strong coupling with light field. Interlayer excitons in heterobilayers, with
layer separation of electron and hole components, feature large electric dipole
that enables strong coupling with electric field and exciton-exciton
interaction, at the cost that the optical dipole is substantially quenched (by
several orders of magnitude). In this letter, we demonstrate the ability to
create a new class of excitons in transition metal dichalcogenide (TMD) hetero-
and homo-bilayers that combines the advantages of monolayer- and
interlayer-excitons, i.e. featuring both large optical dipole and large
electric dipole. These excitons consist of an electron that is well confined in
an individual layer, and a hole that is well extended in both layers, realized
here through the carrier-species specific layer-hybridization controlled
through the interplay of rotational, translational, band offset, and
valley-spin degrees of freedom. We observe different species of such
layer-hybridized valley excitons in different heterobilayer and homobilayer
systems, which can be utilized for realizing strongly interacting
excitonic/polaritonic gases, as well as optical quantum coherent controls of
bidirectional interlayer carrier transfer either with upper conversion or down
conversion in energy
Preparing random state for quantum financing with quantum walks
In recent years, there has been an emerging trend of combining two
innovations in computer science and physics to achieve better computation
capability. Exploring the potential of quantum computation to achieve highly
efficient performance in various tasks is a vital development in engineering
and a valuable question in sciences, as it has a significant potential to
provide exponential speedups for technologically complex problems that are
specifically advantageous to quantum computers. However, one key issue in
unleashing this potential is constructing an efficient approach to load
classical data into quantum states that can be executed by quantum computers or
quantum simulators on classical hardware. Therefore, the split-step quantum
walks (SSQW) algorithm was proposed to address this limitation. We facilitate
SSQW to design parameterized quantum circuits (PQC) that can generate
probability distributions and optimize the parameters to achieve the desired
distribution using a variational solver. A practical example of implementing
SSQW using Qiskit has been released as open-source software. Showing its
potential as a promising method for generating desired probability amplitude
distributions highlights the potential application of SSQW in option pricing
through quantum simulation.Comment: 11 pages, 7 figure
Orthogonal Constant-Amplitude Sequence Families for System Parameter Identification in Spectrally Compact OFDM
In rectangularly-pulsed orthogonal frequency division multiplexing (OFDM)
systems, constant-amplitude (CA) sequences are desirable to construct
preamble/pilot waveforms to facilitate system parameter identification (SPI).
Orthogonal CA sequences are generally preferred in various SPI applications
like random-access channel identification. However, the number of conventional
orthogonal CA sequences (e.g., Zadoff-Chu sequences) that can be adopted in
cellular communication without causing sequence identification ambiguity is
insufficient. Such insufficiency causes heavy performance degradation for SPI
requiring a large number of identification sequences. Moreover,
rectangularly-pulsed OFDM preamble/pilot waveforms carrying conventional CA
sequences suffer from large power spectral sidelobes and thus exhibit low
spectral compactness. This paper is thus motivated to develop several order-I
CA sequence families which contain more orthogonal CA sequences while endowing
the corresponding OFDM preamble/pilot waveforms with fast-decaying spectral
sidelobes. Since more orthogonal sequences are provided, the developed order-I
CA sequence families can enhance the performance characteristics in SPI
requiring a large number of identification sequences over multipath channels
exhibiting short-delay channel profiles, while composing spectrally compact
OFDM preamble/pilot waveforms.Comment: 15 pages, 4 figure
Quantum correlation generation capability of experimental processes
Einstein-Podolsky-Rosen (EPR) steering and Bell nonlocality illustrate two
different kinds of correlations predicted by quantum mechanics. They not only
motivate the exploration of the foundation of quantum mechanics, but also serve
as important resources for quantum-information processing in the presence of
untrusted measurement apparatuses. Herein, we introduce a method for
characterizing the creation of EPR steering and Bell nonlocality for dynamical
processes in experiments. We show that the capability of an experimental
process to create quantum correlations can be quantified and identified simply
by preparing separable states as test inputs of the process and then performing
local measurements on single qubits of the corresponding outputs. This finding
enables the construction of objective benchmarks for the two-qubit controlled
operations used to perform universal quantum computation. We demonstrate this
utility by examining the experimental capability of creating quantum
correlations with the controlled-phase operations on the IBM Quantum Experience
and Amazon Braket Rigetti superconducting quantum computers. The results show
that our method provides a useful diagnostic tool for evaluating the primitive
operations of nonclassical correlation creation in noisy intermediate scale
quantum devices.Comment: 5 figures, 3 appendice
Photoproducts of indomethacin exhibit decreased hydroxyl radical scavenging and xanthine oxidase inhibition activities
AbstractIndomethacin (IN) is a widely used nonsteroidal anti-inflammatory drug. In this study, four photoproducts of IN (IN1–IN4) were produced and isolated from photoirradiated IN. This study investigated the abilities of IN and its photoproducts to scavenge hydroxyl radicals and inhibit xanthine oxidase (XO). The hydroxyl radical-scavenging activity was measured in vitro by electron spin resonance spectrometry using 5,5-dimethyl-1-pyrroline-N-oxide as a spin trapping agent. Enzyme activity was measured by continuous monitoring of uric acid formation, using xanthine as a substrate. The results showed that, among all the related products, IN has the strongest hydroxyl radical-scavenging (IC50 = 65 μM) and XO inhibitory (IC50 = 86 μM) effects. To further understand the stereochemistry of the reactions between these IN derivatives and XO, we performed computer-aided molecular modeling. IN was the most potent inhibitor with the most favorable interaction in the reactive site. Various photoproducts exhibited affinity toward XO as a result of the absence of hydrogen bonding with molybdopterin domain
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