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QUROPE - aggregated feeds in category PhysicsenarXiv.org: Quantum Physics: Many-body Chern number from statistical correlations of randomized measurements. (arXiv:2005.13543v1 [quant-ph])
http://arxiv.org/abs/2005.13543
<p>One of the main topological invariants that characterizes several
topologically-ordered phases is the many-body Chern number (MBCN). Paradigmatic
examples include several fractional quantum Hall phases, which are expected to
be realized in different atomic and photonic quantum platforms in the near
future. Experimental measurement and numerical computation of this invariant is
conventionally based on the linear-response techniques which require having
access to a family of states, as a function of an external parameter, which is
not suitable for many quantum simulators.<p><a href="http://arxiv.org/abs/2005.13543">read more</a></p>
Fri, 29 May 2020 14:52:05 +0200arXiv.org: Quantum Physics: Hydrodynamics of non-integrable systems from relaxation-time approximation. (arXiv:2005.13546v1 [cond-mat.stat-mech])
http://arxiv.org/abs/2005.13546
<p>We develop a general kinetic theory framework to describe the hydrodynamics
of strongly interacting, nonequilibrium quantum systems in which integrability
is weakly broken, leaving a few residual conserved quantities. This framework
is based on a generalized relaxation-time approximation; it gives a simple, but
surprisingly accurate, prescription for computing nonequilibrium transport even
in strongly interacting systems.<p><a href="http://arxiv.org/abs/2005.13546">read more</a></p>
Fri, 29 May 2020 14:52:05 +0200arXiv.org: Quantum Physics: Single-qubit rotations in parameterized quantum circuits. (arXiv:2005.13548v1 [quant-ph])
http://arxiv.org/abs/2005.13548
<p>With the advent of hybrid quantum classical algorithms using parameterized
quantum circuits the question of how to optimize these algorithms and circuits
emerges. In this paper we show that the number of single-qubit rotations in
parameterized quantum circuits can be decreased without compromising the
expressibility or entangling capability of the circuit. We also compare
expressibility and entangling capability across different number of qubits in
parameterized quantum circuits.<p><a href="http://arxiv.org/abs/2005.13548">read more</a></p>
Fri, 29 May 2020 14:52:05 +0200arXiv.org: Quantum Physics: QMetrology from QCosmology: Study with Entangled Two Qubit Open Quantum System in De Sitter Space. (arXiv:2005.13555v1 [hep-th])
http://arxiv.org/abs/2005.13555
<p>In this paper, our prime objective is to apply the techniques of {\it
parameter estimation theory} and the concept of {\it Quantum Metrology} in the
form of {\it Fisher Information} to investigate the role of certain physical
quantities in the open quantum dynamics of a two entangled qubit system under
the Markovian approximation. There exist various physical parameters which
characterize such system, but can not be treated as any quantum mechanical
observable.<p><a href="http://arxiv.org/abs/2005.13555">read more</a></p>
Fri, 29 May 2020 14:52:05 +0200arXiv.org: Quantum Physics: Persistent dark states in anisotropic central spin models. (arXiv:2005.13556v1 [cond-mat.str-el])
http://arxiv.org/abs/2005.13556
<p>Long-lived dark states, in which an experimentally accessible qubit is not in
thermal equilibrium with a surrounding spin bath, are pervasive in solid-state
systems. We explain the ubiquity of dark states in a large class of
inhomogenous central spin models using the proximity to integrable lines with
exact dark eigenstates. At numerically accessible sizes, dark states persist as
eigenstates at large deviations from integrability, and the qubit retains
memory of its initial polarization at long times.<p><a href="http://arxiv.org/abs/2005.13556">read more</a></p>
Fri, 29 May 2020 14:52:05 +0200arXiv.org: Quantum Physics: Scaling up the Anderson transition in random-regular graphs. (arXiv:2005.13571v1 [cond-mat.dis-nn])
http://arxiv.org/abs/2005.13571
<p>We study the Anderson transition in lattices with the connectivity of a
random-regular graph. Our results indicate that fractal dimensions are
continuous across the transition, but a discontinuity occurs in their
derivatives, implying the non-ergodicity of the metal near the Anderson
transition. A critical exponent $\nu = 1.00 \pm0.02$ and critical disorder $W=
18.2\pm 0.1$ are found via a scaling approach. Our data support that the
predictions of the relevant Gaussian Ensemble are only recovered at zero
disorder.
</p>Fri, 29 May 2020 14:52:05 +0200arXiv.org: Quantum Physics: Borromean states in discrete-time quantum walks. (arXiv:2005.13588v1 [quant-ph])
http://arxiv.org/abs/2005.13588
<p>We consider discrete-time quantum walks of many interacting particles. For a
specific kind of pairwise interaction, we find peculiar multipartite bound
states which fall apart if any subsystem is removed. This provides a
conceptually simple physical model of structures known as Borromean rings.
Interestingly, our approach highlights the role of entanglement in such
systems. In order to form a Borromean bound state, the particles need to
exhibit Greenberger-Horne-Zeillinger (GHZ) entanglement. Moreover, we discuss
our findings in the context of formation of composite particles.
</p>Fri, 29 May 2020 14:52:05 +0200arXiv.org: Quantum Physics: Measurement-induced entanglement transitions in many-body localized systems. (arXiv:2005.13603v1 [quant-ph])
http://arxiv.org/abs/2005.13603
<p>The resilience of quantum entanglement to a classicality-inducing environment
is tied to fundamental aspects of quantum many-body systems. The dynamics of
entanglement has recently been studied in the context of measurement-induced
entanglement transitions, where the steady-state entanglement collapses from a
volume-law to an area-law at a critical measurement probability $p_{c}$.
Interestingly, there is a distinction in the value of $p_{c}$ depending on how
well the underlying unitary dynamics scramble quantum information.<p><a href="http://arxiv.org/abs/2005.13603">read more</a></p>
Fri, 29 May 2020 14:52:05 +0200arXiv.org: Quantum Physics: Calculating eigenvalues and eigenvectors of parameter-dependent hamiltonians using an adaptative wave operator method. (arXiv:2005.13611v1 [physics.comp-ph])
http://arxiv.org/abs/2005.13611
<p>We propose a wave operator method to calculate eigenvalues and eigenvectors
of large parameter-dependent matrices, using an adaptative active subspace. We
consider a hamiltonian which depends on external adjustable or adiabatic
parameters, using adaptative projectors which follow the successive eigenspaces
when the adjustable parameters are modified. The method can also handle
non-hermitian hamiltonians. An iterative algorithm is derived and tested
through comparisons with a standard wave operator algorithm using a fixed
active space and with a standard block-Davidson method.<p><a href="http://arxiv.org/abs/2005.13611">read more</a></p>
Fri, 29 May 2020 14:52:05 +0200arXiv.org: Quantum Physics: Finite Quantum Instruments. (arXiv:2005.13642v1 [quant-ph])
http://arxiv.org/abs/2005.13642
<p>This article considers quantum systems described by a finite-dimensional
complex Hilbert space $H$. We first define the concept of a finite observable
on $H$. We then discuss ways of combining observables in terms of convex
combinations, post-processing and sequential products. We also define
complementary and coexistent observables. We then introduce finite instruments
and their related compatible observables. The previous combinations and
relations for observables are extended to instruments and their properties are
compared.<p><a href="http://arxiv.org/abs/2005.13642">read more</a></p>
Fri, 29 May 2020 14:52:05 +0200