3,248 research outputs found
PyCDFT: A Python package for constrained density functional theory
We present PyCDFT, a Python package to compute diabatic states using
constrained density functional theory (CDFT). PyCDFT provides an
object-oriented, customizable implementation of CDFT, and allows for both
single-point self-consistent-field calculations and geometry optimizations.
PyCDFT is designed to interface with existing density functional theory (DFT)
codes to perform CDFT calculations where constraint potentials are added to the
Kohn-Sham Hamiltonian. Here we demonstrate the use of PyCDFT by performing
calculations with a massively parallel first-principles molecular dynamics
code, Qbox, and we benchmark its accuracy by computing the electronic coupling
between diabatic states for a set of organic molecules. We show that PyCDFT
yields results in agreement with existing implementations and is a robust and
flexible package for performing CDFT calculations. The program is available at
https://github.com/hema-ted/pycdft/.Comment: main text: 27 pages, 6 figures supplementary: 7 pages, 2 figure
Steady Bell state generation via magnon-photon coupling
We show that parity-time () symmetry can be spontaneously
broken in the recently reported energy level attraction of magnons and cavity
photons. In the -broken phase, magnon and photon form a
high-fidelity Bell state with maximum entanglement. This entanglement is steady
and robust against the perturbation of environment, in contrast to the general
wisdom that expects instability of the hybridized state when the symmetry is
broken. This anomaly is further understood by the compete of non-Hermitian
evolution and particle number conservation of the hybridized system. As a
comparison, neither -symmetry broken nor steady magnon-photon
entanglement is observed inside the normal level repulsion case. Our results
may open a novel window to utilize magnon-photon entanglement as a resource for
quantum technologies.Comment: 5 pages, 4 figure
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