KNAPIK Joachim
Position : doctorant
Team: Astrophysique Stellaire
joachim.knapik

umontpellier.fr
0675190698
Research Topics: - phys/phys.phys/phys.phys.phys-atm-ph
- phys/phys.phys/phys.phys.phys-chem-ph
- phys/phys.phys/phys.phys.phys-comp-ph
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Scientific productions :

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Quantum Dynamics of Chemical Reactions of
Astrophysical Interest Within a Reaction Path Framework
Author(s): Knapik J. , Lauvergnat David, Scribano Y.
(Posters)
Colloque du programme physique chimie du milieu interstellaire (Bordeaux, FR), 2024
Abstract: The chemical reactions occurring in the astrophysical context are at the
origin of the molecular complexity observed in these environments[1]. These
chemical reactions are characterised by their thermal rate constants, which can be
theoretically determined with quantum dynamics simulations. State-of-the-art, in
quantum dynamics methods, remains the Close-Coupling approach[2-3] but is
mainly limited to triatomic species (due to their computational cost) and requires a
global potential energy surface. Although very accurate, this method is not suitable
for more complex molecular systems and new computational methods,
approximated but accurate, are needed.
We propose a new set of curvilinear coordinates transformations[4] that
enable us to perform quantum dynamics simulations following a minimum energy
path. This approach do not require a full global potential energy surface
calculation. This set of curvilinear coordinates are combined with a direct
determination of the thermal rate constant using the Green's operator formulation
with complex absorbing potentials[5] avoiding the full S-matrix computation. The
efficiency of this new scheme is demonstrated on the collinear chemical reaction H
+ H2 → H2 + H for which accurate close-coupling results are available [6,7].
Furthermore, our computational scheme can be efficiently combined with a
reduced dimensional model for complex chemical reactions.
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On the mapping of a vibrational Hamiltonian model on a
quantum computer
Author(s): Knapik J. , Lasorne Benjamin, Senjean Bruno, Scribano Y.
(Posters)
ThéMoSiA-RCTF2024 (Rouen, FR), 2024-06-24
Abstract: As a relatively new topic, simulation of the vibrational structure problem with qubit-based quantum computers
raises several questions 1,2. Unlike the fermionic particules in electronic structure, bosons do not follow the Pauli
exclusion principle. For the simulation of fermions one can map directly the occupation of a spin orbital or the
parity on the state of a qubit. Mapping a bosonic system, wich is a more than two-level system, on a qubit basis
is not straightforward and encodings that overcomes this issue have been developed 3,4. Here we present some of
these encodings with their advantages and drawbacks. To do so, we focus on a one mode tunnelling system, with
a double-well potential using an harmonic oscillator basis set. We highlight the importance of ordering operators
in the second quantized formulation of the Hamiltonian, due to the truncation of the supposed infinite basis. Our
study point out that significant errors occur, in the eigenvalues computation, if the second quantized Hamiltonian
is not properly ordered
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