1,776 research outputs found
Simulation of mirror inversion of quantum states in an XY spin chain using NMR
We report an experimental quantum simulation of unitary dynamics of an XY
spin chain with pre-engineered couplings. Using this simulation, we demonstrate
the mirror inversion of quantum states, proposed by Albanese et al. [Phys. Rev.
Lett. 93, 230502 (2004)]. The experiment is performed with a 5-qubit dipolar
coupled spin system using nuclear magnetic resonance techniques. To perform
quantum simulation we make use of the recently proposed unitary operator
decomposition algorithm of Ajoy et al. [Phys. Rev. A 85, 030303 (2012)] along
with numerical pulse optimization techniques. Further, using mirror inversion,
we demonstrate that entangled states can be transferred from one end of the
chain to the other end. The simulations are implemented with high experimental
fidelity, which implies that these kind of simulations may be possible in
larger systems.Comment: 9 pages, 6 figure
Anomalous Raman scattering from phonons and electrons of superconducting FeSe
We report interesting anomalies in the temperature dependent Raman spectra of
FeSe measured from 3K to 300K in the spectral range from 60 to 1800
cm and determine their origin using complementary first-principles
density functional calculations. A phonon mode near 100 cm exhibits a
sharp increase by 5% in frequency below a temperature T ( 100
K) attributed to strong spin-phonon coupling and onset of short-range
antiferromagnetic order. In addition, two high frequency modes are observed at
1350 cm and 1600 cm, attributed to electronic Raman scattering
from ()to / -orbitals of Fe.Comment: 19 pages, 4 figures, 1 tabl
Metallic monoclinic phase in VO induced by electrochemical gating: in-situ Raman study
We report in-situ Raman scattering studies of electrochemically top gated
VO thin film to address metal-insulator transition (MIT) under gating. The
room temperature monoclinic insulating phase goes to metallic state at a gate
voltage of 2.6 V. However, the number of Raman modes do not change with
electrolyte gating showing that the metallic phase is still monoclinic. The
high frequency Raman mode A(7) near 616 cm ascribed to V-O vibration
of bond length 2.06 \AA~ in VO octahedra hardens with increasing gate
voltage and the B(3) mode near 654 cm softens. This shows that the
distortion of the VO octahedra in the monoclinic phase decreases with
gating. The time dependent Raman data at fixed gate voltages of 1 V (for 50
minute, showing enhancement of conductivity by a factor of 50) and 2 V (for 130
minute, showing further increase in conductivity by a factor of 5) show similar
changes in high frequency Raman modes A(7) and B(3) as observed in
gating. This slow change in conductance together with Raman frequency changes
show that the governing mechanism for metalization is more likely to the
diffusion controlled oxygen vacancy formation due to the applied electric
field.Comment: 5 pages, 6 figure
Neutron-Proton Scattering Phase Shifts in S-Channel using Phase Function Method for Various Two Term Potentials
The scattering phase shifts for n-p scattering have been modeled using various two term exponential type potentials such as Malfliet-Tjon, Manning-Rosen and Morse to study the phase shifts in the S-channels. As a first step, the model arameters for each of the potentials are determined by obtaining binding energy of the deuteron using matrix methods vis-a-vis Variational Monte-Carlo (VMC) technique to minimize the percentage error w.r.t. the experimental value. Then, the first order ODE as given by phase function method (PFM), is numerically solved using 5th order Runge-Kutta (RK-5) technique, by substituting the obtained potentials for calculating phase shifts for the bound 3S1 channel. Finally, the potential parameters are varied in least squares sense using VMC technique to obtain the scattering phase-shifts for each of the potentials in the 1S0 channel. The numerically obtained values are seen to be matching with those obtained using other analytical techniques and a comparative analysis with the experimental values up to 300 MeV is presented
Deuteron Structure and Form Factors: Using Inverse Potentials for S-waves
In this paper, we determine deuteron's static properties, low energy
scattering parameters, total cross-section and form factors from inverse S-wave
potentials constructed using Morse function. The scattering phase shifts (SPS)
at different lab energies are determined using phase function method. The model
parameters are optimised using both machine learning algorithm and traditional
data analysis by choosing mean squared error as cost function. The mean
absolute error between experimental and obtained SPS for states 3S1 and 1S0 are
found to be 0.35 and 0.70 respectively. The low energy scattering parameters
are matching well with expected values. The contribution due to S-waves SPS
towards total cross-section at various energies have been obtained and are
matching well with experimental values. The analytical ground state deuteron
wave-function (DWF) is obtained by utilizing the experimental value for
Quadrupole moment. Other static properties and form factors determined from
obtained DWF are found to be in close agreement with experimental ones.Comment: 29 pages, 5 Figures, 8 Table
Monogamy of quantum correlations reveals frustration in a quantum Ising spin system: Experimental demonstration
We report a nuclear magnetic resonance experiment, which simulates the
quantum transverse Ising spin system in a triangular configuration and further
show that the monogamy of quantum correlations can be used to distinguish
between the frustrated and non-frustrated regimes in the ground state of this
system. Adiabatic state preparation methods are used to prepare the ground
states of the spin system. We employ two different multipartite quantum
correlation measures to analyze the experimental ground state of the system in
both the frustrated and non-frustrated regimes. In particular, we use
multipartite quantum correlation measures generated by monogamy considerations
of negativity, a bipartite entanglement measure, and that of quantum discord,
an information-theoretic quantum correlation measure. As expected from
theoretical predictions, the experimental data confirm that the non-frustrated
regime shows higher multipartite quantum correlations compared to the
frustrated one.Comment: Title in the published version is "Multipartite quantum correlations
reveal frustration in a quantum Ising spin system", 7 pages, 4 figure
Private Ownership of Grazing Land in Tropical Semi‐Arid Tract Spurs Community Action for Sustainable Management of Grassland
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