8 research outputs found
Learning the tensor network model of a quantum state using a few single-qubit measurements
The constantly increasing dimensionality of artificial quantum systems
demands for highly efficient methods for their characterization and
benchmarking. Conventional quantum tomography fails for larger systems due to
the exponential growth of the required number of measurements. The conceptual
solution for this dimensionality curse relies on a simple idea - a complete
description of a quantum state is excessive and can be discarded in favor of
experimentally accessible information about the system. The probably
approximately correct (PAC) learning theory has been recently successfully
applied to a problem of building accurate predictors for the measurement
outcomes using a dataset which scales only linearly with the number of qubits.
Here we present a constructive and numerically efficient protocol which learns
a tensor network model of an unknown quantum system. We discuss the limitations
and the scalability of the proposed method.Comment: 10 pages, 11 figure
Observation of edge solitons in topological trimer arrays
We report the experimental observation of nonlinear light localization and edge soliton formation at the edges of fs-laser written trimer waveguide arrays, where transition from nontopological to topological phases is controlled by the spacing between neighboring trimers. We found that, in the former regime, edge solitons occur only above a considerable power threshold, whereas in the latter one they bifurcate from linear states. Edge solitons are observed in a broad power range where their propagation constant falls into one of the topological gaps of the system, while partial delocalization is observed when considerable nonlinearity drives the propagation constant into an allowed band, causing coupling with bulk modes. Our results provide direct experimental evidence of the coexistence and selective excitation in the same or in different topological gaps of two types of topological edge solitons with different internal structures, which can rarely be observed even in nontopological systems. This also constitutes the first experimental evidence of formation of topological solitons in a nonlinear system with more than one topological gap.The authors acknowledge funding of this study by RSF (grant 21‐12‐00096). Also, support by CEX2019‐000910‐S [funded by MCIN/AEI/10.13039/501100011033], Fundació Cellex, Fundació Mir‐Puig, and Generalitat de Catalunya (CERCA) is acknowledged.Peer ReviewedPostprint (author's final draft
Observation of solitons in oscillating waveguide arrays
Floquet systems with periodically varying in time parameters enable
realization of unconventional topological phases that do not exist in static
systems with constant parameters and that are frequently accompanied by
appearance of novel types of the topological states. Among such Floquet systems
are the Su-Schrieffer-Heeger lattices with periodically-modulated couplings
that can support at their edges anomalous modes of topological origin
despite the fact that the lattice spends only half of the evolution period in
topologically nontrivial phase, while during other half-period it is
topologically trivial. Here, using Su-Schrieffer-Heeger arrays composed from
periodically oscillating waveguides inscribed in transparent nonlinear optical
medium, we report experimental observation of photonic anomalous modes
residing at the edge or in the corner of the one- or two-dimensional arrays,
respectively, and demonstrate a new class of topological solitons
bifurcating from such modes in the topological gap of the Floquet spectrum at
high powers. solitons reported here are strongly oscillating nonlinear
Floquet states exactly reproducing their profiles after each longitudinal
period of the structure. They can be dynamically stable in both one- and
two-dimensional oscillating waveguide arrays, the latter ones representing the
first realization of the Floquet photonic higher-order topological insulator,
while localization properties of such solitons are determined by their
power.Comment: 10 pages, 6 figures, to appear in Science Bulleti
Observation of linear and nonlinear light localization at the edges of moiré arrays
We observe linear and nonlinear light localization at the edges and in the corners of truncated moiré arrays created by the superposition of periodic mutually twisted at Pythagorean angles square sublattices. Experimentally exciting corner linear modes in the femtosecond-laser written moiré arrays we find drastic differences in their localization properties in comparison with the bulk excitations. We also address the impact of nonlinearity on the corner and bulk modes and experimentally observe the crossover from linear quasilocalized states to the surface solitons emerging at the higher input powers. Our results constitute the first experimental demonstration of localization phenomena induced by truncation of periodic moiré structures in photonic systems.This research is funded by the research Project No. FFUU- 2021-0003 of the Institute of Spectroscopy of the Russian Academy of Sciences and partially funded by the RSF Grant No. 21-12-00096. F. Y. acknowledges support from Shanghai Outstanding Academic Leaders Plan (Grant No. 20XD1402000) and the NSFC (Grant No. 91950120). S. K. I. and L. T. acknowledge support by Grants No. CEX2019-000910-S and No. PGC2018-097035-B-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER, Fundació Cellex, Fundació Mir-Puig, and Generalitat de Catalunya (CERCA).Peer ReviewedPostprint (published version
Benchmarking a boson sampler with Hamming nets
Analyzing the properties of complex quantum systems is crucial for further
development of quantum devices, yet this task is typically challenging and
demanding with respect to required amount of measurements. A special attention
to this problem appears within the context of characterizing outcomes of noisy
intermediate-scale quantum devices, which produce quantum states with specific
properties so that it is expected to be hard to simulate such states using
classical resources. In this work, we address the problem of characterization
of a boson sampling device, which uses interference of input photons to produce
samples of non-trivial probability distributions that at certain condition are
hard to obtain classically. For realistic experimental conditions the problem
is to probe multi-photon interference with a limited number of the measurement
outcomes without collisions and repetitions. By constructing networks on the
measurements outcomes, we demonstrate a possibility to discriminate between
regimes of indistinguishable and distinguishable bosons by quantifying the
structures of the corresponding networks. Based on this we propose a
machine-learning-based protocol to benchmark a boson sampler with unknown
scattering matrix. Notably, the protocol works in the most challenging regimes
of having a very limited number of bitstrings without collisions and
repetitions. As we expect, our framework can be directly applied for
characterizing boson sampling devices that are currently available in
experiments.Comment: 14 page
Observation of rotation-induced light localization in waveguide arrays
We study both, experimentally and theoretically, propagation of light in the
fs-laser written rotating square waveguide arrays and present the first
experimental evidence of light localization induced by the rotation of periodic
structure in the direction of light propagation. Such linear light localization
occurs either in the corners of truncated square array, where it results from
the interplay between the centrifugal effect and total internal reflection at
the borders of truncated array, or in the center of array, where rotation
creates effective attractive optical potential. The degree of localization of
linear bulk and corner modes emerging due to the rotation increases with the
increase of rotation frequency. Consequently, corner and bulk solitons in
rotating wave-guide arrays become thresholdless for sufficiently large rotation
frequencies, in contrast to solitons in non-rotating arrays that exist only
above power threshold. Focusing nonlinearity enhances localization degree of
corner modes, but surprising initially it leads to broadening of bulk nonlinear
states, followed by their re-localization at high input powers. Our results
open new prospects for control of evolution of nonlinear multidimensional
excitations by dynamically varying potentials.Comment: 7 pages, 5 figures, to be appear on ACS Photonic
Extracellular vesicles of human glial cells exert neuroprotective effects via brain miRNA modulation in a rat model of traumatic brain injury
Abstract Stem cell-based therapeutic approaches for neurological disorders are widely studied. Paracrine factors secreted by stem cells in vitro and delivered intranasally might allow bypassing the disadvantages associated with a surgical cell delivery procedure with likely immune rejection of a transplant. In this study, we investigated the therapeutic effect of the extracellular vesicles secreted by glial progenitor cells (GPC-EV) derived from human induced pluripotent stem cell in a traumatic brain injury model. Intranasal administration of GPC-EV to Wistar rats for 6 days improved sensorimotor functions assessed over a 14-day observation period. Beside, deep sequencing of microRNA transcriptome of GPC-EV was estimate, and was revealed 203 microRNA species that might be implicated in prevention of various brain pathologies. Modulation of microRNA pools might contribute to the observed decrease in the number of astrocytes that inhibit neurorecovery processes while enhancing neuroplasticity by decreasing phosphorylated Tau forms, preventing inflammation and apoptosis associated with secondary damage to brain tissue. The course of GPC-EV administration was promoted the increasing protein levels of NF-κB in studied areas of the rat brain, indicating NF-κB dependent mechanisms as a plausible route of neuroprotection within the damaged area. This investigation showed that GPC-EV may be representing a therapeutic approach in traumatic brain injury, though its translation into the clinic would require an additional research and development