120 research outputs found
Experimental localisation of quantum entanglement through monitored classical mediator
Quantum entanglement is a form of correlation between quantum particles that
cannot be increased via local operations and classical communication. It has
therefore been proposed that an increment of quantum entanglement between
probes that are interacting solely via a mediator implies non-classicality of
the mediator. Indeed, under certain assumptions regarding the initial state,
entanglement gain between the probes indicates quantum coherence in the
mediator. Going beyond such assumptions, there exist other initial states which
produce entanglement between the probes via only local interactions with a
classical mediator. In this process the initial entanglement between any probe
and the rest of the system ``flows through'' the classical mediator and gets
localised between the probes. Here we theoretically characterise maximal
entanglement gain via classical mediator and experimentally demonstrate, using
liquid-state NMR spectroscopy, the optimal growth of quantum correlations
between two nuclear spin qubits interacting through a mediator qubit in a
classical state. We additionally monitor, i.e., dephase, the mediator in order
to emphasise its classical character. Our results indicate the necessity of
verifying features of the initial state if entanglement gain between the probes
is used as a figure of merit for witnessing non-classical mediator. Such
methods were proposed to have exemplary applications in quantum optomechanics,
quantum biology and quantum gravity.Comment: 5 pages, 2 figure
Solving hadron structures using the basis light-front quantization approach on quantum computers
Quantum computing has demonstrated the potential to revolutionize our
understanding of nuclear, atomic, and molecular structure by obtaining
forefront solutions in non-relativistic quantum many-body theory. In this work,
we show that quantum computing can be used to solve for the structure of
hadrons, governed by strongly-interacting relativistic quantum field theory.
Following our previous work on light unflavored mesons as a relativistic
bound-state problem within the nonperturbative Hamiltonian formalism, we
present the numerical calculations on simulated quantum devices using the basis
light-front quantization (BLFQ) approach. We implement and compare the
variational quantum eigensolver (VQE) and the subspace-search variational
quantum eigensolver (SSVQE) to find the low-lying mass spectrum of the light
meson system and its corresponding light-front wave functions as quantum states
from ideal simulators, noisy simulators, and IBM quantum computers. Based on
obtained quantum states, we evaluate the meson decay constants and parton
distribution functions directly on the quantum circuits. Our calculations on
the quantum computers and simulators are in reasonable agreement with accurate
numerical solutions solved on classical computers when noises are moderately
small, and our overall results are comparable with the available experimental
data.Comment: 20 pages, 8 figure
Ab Initio No Core Shell Model with Leadership-Class Supercomputers
Nuclear structure and reaction theory is undergoing a major renaissance with
advances in many-body methods, strong interactions with greatly improved links
to Quantum Chromodynamics (QCD), the advent of high performance computing, and
improved computational algorithms. Predictive power, with well-quantified
uncertainty, is emerging from non-perturbative approaches along with the
potential for guiding experiments to new discoveries. We present an overview of
some of our recent developments and discuss challenges that lie ahead. Our foci
include: (1) strong interactions derived from chiral effective field theory;
(2) advances in solving the large sparse matrix eigenvalue problem on
leadership-class supercomputers; (3) selected observables in light nuclei with
the JISP16 interaction; (4) effective electroweak operators consistent with the
Hamiltonian; and, (5) discussion of A=48 system as an opportunity for the
no-core approach with the reintroduction of the core.Comment: 23 pages, 7 figures, Conference Proceedings online at
http://ntse.khb.ru/files/uploads/2016/proceedings/Vary.pd
Magnetic moments of nuclei with chiral effective field theory operators
Chiral effective field theory (EFT) provides a framework for obtaining
internucleon interactions in a systematically improvable fashion from first
principles, while also providing for the derivation of consistent electroweak
current operators. In this work, we apply consistently derived interactions and
currents towards calculating the magnetic dipole moments of the systems
Triton and Helium-3. We focus here on LENPIC interactions obtained using
semilocal coordinate-space (SCS) regularization. Starting from the
momentum-space representation of the LENPIC EFT vector current, we derive
the SCS-regularized magnetic dipole operator up through N2LO. We then carry out
no-core shell model calculations for Triton and Helium-3 systems, using the SCS
LENPIC interaction at N2LO in EFT, and evaluate the magnetic dipole
moments obtained using the consistently derived one-nucleon and two-nucleon
electromagnetic currents. As anticipated by prior results with EFT
currents, the current corrections through N2LO provide improved, but not yet
complete, agreement with experiment for the Triton and Helium-3 magnetic dipole
moments.Comment: 30 pages, 2 figure
Calculations of reaction in chiral effective field theory
We present a calculation of the radiative capture cross section in the low-energy range, where the reaction channel dominates.
Employing the LENPIC nucleon-nucleon interaction up to the fifth order (N4LO)
that is regularized by the semi-local coordinate space regulators, we obtain
the initial and final state wave functions, and evaluate the phase shifts of
the scattering state and deuteron properties. We derive the transition operator
from the chiral effective field theory up to the next-to-next-to leading order
(N2LO), where we also regularize the transition operator using regulators
consistent with those of the interactions. We compute the capture cross
sections and the results show a converging pattern with the chiral-order
expansion of the nucleon-nucleon interaction, where the regulator dependence of
the results is weak when higher-order nucleon-nucleon interactions are
employed. We quantify the uncertainties of the cross-section results due to the
chiral-order truncation. The chirally complete and consistent cross-section
results are performed up to N2LO and they compare well with the experiments and
other theoretical predictions.Comment: 13 pages, 3 tables, 1 figur
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