27 research outputs found
Dual Exponential Coupled Cluster Theory: Unitary Adaptation, Implementation in the Variational Quantum Eigensolver Framework and Pilot Applications
In this paper, we have developed a unitary variant of a double exponential
coupled cluster theory, which is capable of mimicking the effects of connected
excitations of arbitrarily high rank, using only rank-one and rank-two
parametrization of the wavefunction ansatz. While its implementation in a
classical computer necessitates the construction of an effective Hamiltonian
which involves infinite number of terms with arbitrarily high many-body rank,
the same can easily be implemented in the hybrid quantum-classical variational
quantum eigensolver framework with a reasonably shallow quantum circuit. The
method relies upon the nontrivial action of a unitary, containing a set of
rank-two scattering operators, on entangled states generated via cluster
operators. We have further introduced a number of variants of the ansatz with
different degrees of expressibility by judiciously approximating the scattering
operators. With a number of applications on strongly correlated molecules, we
have shown that all our schemes can perform uniformly well throughout the
molecular potential energy surface without significant additional
implementation cost and quantum complexity over the unitary coupled cluster
approach with single and double excitations
Relativistic calculations of molecular electric dipole moments of singly charged aluminium monohalides
In this work, we have studied the permanent electric dipole moments of singly
charged aluminium monohalides in their electronic ground state, X,
using Kramers-restricted relativistic configuration interaction method. We
report our results from this method in the singles and doubles approximation
with those of Dirac-Fock calculations. For our finite field computations,
quadruple zeta basis sets were employed. We discuss the electron correlation
trends that we find in our calculated properties and have compared our results
with those from literature, wherever available.Comment: 6 pages, 2 figures, 2 table
Molecular electric dipole moments: from light to heavy molecules using a relativistic VQE algorithm
The quantum-classical hybrid Variational Quantum Eigensolver (VQE) algorithm
is recognized to be the most suitable approach to obtain ground state energies
of quantum many-body systems in the noisy intermediate scale quantum era. In
this work, we extend the VQE algorithm to the relativistic regime and carry out
quantum simulations to obtain ground state energies as well as molecular
permanent electric dipole moments of single-valence diatomic molecules,
beginning with the light BeH molecule and all the way to the heavy radioactive
RaH molecule. We study the correlation trends in these systems as well as
assess the precision in our results within our active space of 12 qubits