29 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
Time-domain Hong-Ou-Mandel interference of quasi-thermal fields and its application in linear optical circuit characterization
We study temporal correlations of interfering quasi-thermal fields, obtained
by scattering laser radiation on a rotating ground glass disk. We show that the
Doppler effect causes oscillations in temporal cross-correlation function.
Furthermore, we propose how to use Hong-Ou-Mandel interference of quasi-thermal
fields in the time domain to characterize linear optical circuits.Comment: 8 pages, 5 figures (main), 4 pages, 1 figure (supplemental
Employee skills for circular business model implementation: A taxonomy
A growing body of scholarship has examined circular business models as a pathway towards sustainability. However, employee skills to support such business models have been largely overlooked. Addressing this research gap, this article proposes a comprehensive skill taxonomy for start-ups embracing circular economy transition. As the first large-N effort to develop a comprehensive skill taxonomy for circular business model implementation, this study uses a clustering analysis of self-reported skill profiles for 2407 staff working in circular start-ups. The taxonomy outlines 40 skills across six categories: business innovation, operations, social dimensions, systems, digitization, and technical issues. Findings suggest that circular business model implementation requires a set of general, sustainable, and circular skills, but some of these skills have been neglected in scholarship. Promoting circular narratives as a framing device for skill development can help advance CE towards mainstream uptake, and this study's taxonomy offers a practical framework for using talent to accelerate CE transition
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 nonlinear fractal higher-order topological insulator
Higher-order topological insulators (HOTIs) are unique materials hosting
topologically protected states, whose dimensionality is at least by a factor of
2 lower than that of the bulk. Topological states in such insulators may be
strongly confined in their corners that leads to considerable enhancement of
nonlinear processes involving such states. However, all nonlinear HOTIs
demonstrated so far were built on periodic bulk lattice materials. Here we
demonstrate first \textit{nonlinear photonic} HOTI with the fractal origin.
Despite their fractional effective dimensionality, the HOTIs constructed here
on two different types of the Sierpi\'nski gasket waveguide arrays, may support
topological corner states for unexpectedly wide range of coupling strengths,
even in parameter regions where conventional HOTIs become trivial. We
demonstrate thresholdless solitons bifurcating from corner states in nonlinear
fractal HOTIs and show that their localization can be efficiently controlled by
the input beam power. We observe sharp differences in nonlinear light
localization on outer and multiple inner corners and edges representative for
these fractal materials. Our findings not only represent a new paradigm for
nonlinear topological insulators, but also open new avenues for potential
applications of fractal materials to control the light flow.Comment: 10 pages, 5 figure