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Papers by Stéphane Vranckx
Advances in Atom and Single Molecule Machines, 2012
ABSTRACT We numerically investigate the implementation of small quantum algorithms, an arithmetic... more ABSTRACT We numerically investigate the implementation of small quantum algorithms, an arithmetic adder and the Grover search algorithm, in registers of ultracold polar molecules trapped in a lattice by concatenating intramolecular and intermolecular gates. The molecular states are modulated by the exposition to static electric and magnetic fields different for each molecule. The examples are carried out in a two-molecule case. Qubits are encoded either in rovibrational or in hyperfine states, and intermolecular gates involve states of neighboring molecules. Here we use π pulses (i.e., laser pulses such that the integral of the product of the transition dipole moment and their envelope is equal to π, thus ensuring a total population inversion between two states) and pulses designed by optimal control theory adapted to a multi-target problem to drive unitary transformations between the qubit states.
Proceedings of The International Astronomical Union, 2011
According to models, the HeH^+ cation is the first molecular species to have formed in the early ... more According to models, the HeH^+ cation is the first molecular species to have formed in the early universe, by radiative association of H^+ with He or H with He^+. Although it is predicted to be abundant in He-rich astrophysical environments, such as planetary nebula NGC7027, it has so far eluded extra-terrestrial observation. It is proposed here that the HeH^+ ion
The Journal of Physical Chemistry A, 2013
We investigate the photodissociation of the metastable triplet state of HeH + as well as its form... more We investigate the photodissociation of the metastable triplet state of HeH + as well as its formation through the inverse process, radiative association. In models of astrophysical plasmas, HeH + is assumed to be present only in the ground state, and the influence of the triplet state has not been explored. It may be formed by radiative association during collisions between a proton and metastable helium, which are present in significant concentrations in nebulae. The triplet state can also be formed by association of He + and H, although this process is less likely to occur. We compute the cross sections and rate coefficients corresponding to the photodissociation of the triplet state by UV photons from a central star using a wave packet method. We show that the photodissociation cross sections depend strongly on the initial vibrational state and that the effects of excited electronic states and non-adiabatic couplings cannot be neglected. We then calculate the cross section and rate coefficient for the radiative association of HeH + in the metastable triplet state.
Theoretical Chemistry Accounts, 2012
... jlievin@ulb.ac.be 1 Not to be confused with the Atoms In Molecules (AIM) approach of the late... more ... jlievin@ulb.ac.be 1 Not to be confused with the Atoms In Molecules (AIM) approach of the late Richard Bader [6]. 123 Theor Chem Acc (2012) 131:1254 DOI10.1007/s00214-012-1254-3 Page 2. effects [71], the characterization ...
According to models, the HeH^+ cation is the first molecular species to have formed in the early ... more According to models, the HeH^+ cation is the first molecular species to have formed in the early universe, by radiative association of H^+ with He or H with He^+. Although it is predicted to be abundant in He-rich astrophysical environments, such as planetary nebula NGC7027, it has so far eluded extra-terrestrial observation. It is proposed here that the HeH^+ ion
Journal of Physics: Conference Series, 2012
ABSTRACT We implement a local control strategy based on the use of Møller operators and use it to... more ABSTRACT We implement a local control strategy based on the use of Møller operators and use it to control the photodissociation of diatomic molecules in the presence of nonadiabatic interactions.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2013
Proceedings of The International Astronomical Union, 2011
According to models, the HeH^+ cation is the first molecular species to have formed in the early ... more According to models, the HeH^+ cation is the first molecular species to have formed in the early universe, by radiative association of H^+ with He or H with He^+. Although it is predicted to be abundant in He-rich astrophysical environments, such as planetary nebula NGC7027, it has so far eluded extra-terrestrial observation. It is proposed here that the HeH^+ ion could be detected in its a ^3Σ^+ metastable state, as it has a long lifetime (< 100 s). The first superior electronic state of the same symmetry, the b ^3Σ^+ state, has a much shorter lifetime (≈ 10-8 s) and will thus populate the a state radiatively. We investigate the formation of HeH^+ in the a and b ^3Σ^+ states by radiative stabilization and their destruction by photodissociation using time-dependent quantum dynamics. The partial photodissociation cross-sections from all their vibrational levels towards the ten ^3Σ^+ and the six ^3Π superior states are calculated, from which the corresponding radiative stabilization cross-sections are then inferred. The rate constant for both processes is estimated in the range of temperature and of radiative energy distribution found in planetary nebulae. It is shown that the vibrational dependence of the radiative stabilization cross-section, usually neglected in the estimation of the rate constant, has a significant impact at low temperature.
Physical Chemistry Chemical Physics, 2011
We numerically implement quantum algorithms in hyperfine levels of ultracold polar molecules. Log... more We numerically implement quantum algorithms in hyperfine levels of ultracold polar molecules. Logical operations are driven by pulses optimized by optimal control theory. All implementations take place in the lowest two rotational levels of the ground vibrational state of the ground (1)Σ(+) electronic state, exploiting the richness of the hyperfine energy structure and state mixing in static external fields. We show that it is possible to realize high fidelity complex logical operations with microsecond pulses. The possibility to run algorithms implemented on two interacting molecules is also demonstrated. (41)K(85)Rb and (41)K(87)Rb molecules are considered for the numerical simulations but the results are general and can be extended to other species.
Theoretica Chimica Acta, Jan 1, 2012
... jlievin@ulb.ac.be 1 Not to be confused with the Atoms In Molecules (AIM) approach of the late... more ... jlievin@ulb.ac.be 1 Not to be confused with the Atoms In Molecules (AIM) approach of the late Richard Bader [6]. 123 Theor Chem Acc (2012) 131:1254 DOI10.1007/s00214-012-1254-3 Page 2. effects [71], the characterization ...
Physical Chemistry Chemical Physics, Nov 14, 2011
We numerically implement quantum algorithms in hyperfine levels of ultracold polar molecules. Log... more We numerically implement quantum algorithms in hyperfine levels of ultracold polar molecules. Logical operations are driven by pulses optimized by optimal control theory. All implementations take place in the lowest two rotational levels of the ground vibrational state of the ground (1)Σ(+) electronic state, exploiting the richness of the hyperfine energy structure and state mixing in static external fields. We show that it is possible to realize high fidelity complex logical operations with microsecond pulses. The possibility to run algorithms implemented on two interacting molecules is also demonstrated. (41)K(85)Rb and (41)K(87)Rb molecules are considered for the numerical simulations but the results are general and can be extended to other species.
Conference Presentations by Stéphane Vranckx
Advances in Atom and Single Molecule Machines, 2012
ABSTRACT We numerically investigate the implementation of small quantum algorithms, an arithmetic... more ABSTRACT We numerically investigate the implementation of small quantum algorithms, an arithmetic adder and the Grover search algorithm, in registers of ultracold polar molecules trapped in a lattice by concatenating intramolecular and intermolecular gates. The molecular states are modulated by the exposition to static electric and magnetic fields different for each molecule. The examples are carried out in a two-molecule case. Qubits are encoded either in rovibrational or in hyperfine states, and intermolecular gates involve states of neighboring molecules. Here we use π pulses (i.e., laser pulses such that the integral of the product of the transition dipole moment and their envelope is equal to π, thus ensuring a total population inversion between two states) and pulses designed by optimal control theory adapted to a multi-target problem to drive unitary transformations between the qubit states.
Proceedings of The International Astronomical Union, 2011
According to models, the HeH^+ cation is the first molecular species to have formed in the early ... more According to models, the HeH^+ cation is the first molecular species to have formed in the early universe, by radiative association of H^+ with He or H with He^+. Although it is predicted to be abundant in He-rich astrophysical environments, such as planetary nebula NGC7027, it has so far eluded extra-terrestrial observation. It is proposed here that the HeH^+ ion
The Journal of Physical Chemistry A, 2013
We investigate the photodissociation of the metastable triplet state of HeH + as well as its form... more We investigate the photodissociation of the metastable triplet state of HeH + as well as its formation through the inverse process, radiative association. In models of astrophysical plasmas, HeH + is assumed to be present only in the ground state, and the influence of the triplet state has not been explored. It may be formed by radiative association during collisions between a proton and metastable helium, which are present in significant concentrations in nebulae. The triplet state can also be formed by association of He + and H, although this process is less likely to occur. We compute the cross sections and rate coefficients corresponding to the photodissociation of the triplet state by UV photons from a central star using a wave packet method. We show that the photodissociation cross sections depend strongly on the initial vibrational state and that the effects of excited electronic states and non-adiabatic couplings cannot be neglected. We then calculate the cross section and rate coefficient for the radiative association of HeH + in the metastable triplet state.
Theoretical Chemistry Accounts, 2012
... jlievin@ulb.ac.be 1 Not to be confused with the Atoms In Molecules (AIM) approach of the late... more ... jlievin@ulb.ac.be 1 Not to be confused with the Atoms In Molecules (AIM) approach of the late Richard Bader [6]. 123 Theor Chem Acc (2012) 131:1254 DOI10.1007/s00214-012-1254-3 Page 2. effects [71], the characterization ...
According to models, the HeH^+ cation is the first molecular species to have formed in the early ... more According to models, the HeH^+ cation is the first molecular species to have formed in the early universe, by radiative association of H^+ with He or H with He^+. Although it is predicted to be abundant in He-rich astrophysical environments, such as planetary nebula NGC7027, it has so far eluded extra-terrestrial observation. It is proposed here that the HeH^+ ion
Journal of Physics: Conference Series, 2012
ABSTRACT We implement a local control strategy based on the use of Møller operators and use it to... more ABSTRACT We implement a local control strategy based on the use of Møller operators and use it to control the photodissociation of diatomic molecules in the presence of nonadiabatic interactions.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2013
Proceedings of The International Astronomical Union, 2011
According to models, the HeH^+ cation is the first molecular species to have formed in the early ... more According to models, the HeH^+ cation is the first molecular species to have formed in the early universe, by radiative association of H^+ with He or H with He^+. Although it is predicted to be abundant in He-rich astrophysical environments, such as planetary nebula NGC7027, it has so far eluded extra-terrestrial observation. It is proposed here that the HeH^+ ion could be detected in its a ^3Σ^+ metastable state, as it has a long lifetime (< 100 s). The first superior electronic state of the same symmetry, the b ^3Σ^+ state, has a much shorter lifetime (≈ 10-8 s) and will thus populate the a state radiatively. We investigate the formation of HeH^+ in the a and b ^3Σ^+ states by radiative stabilization and their destruction by photodissociation using time-dependent quantum dynamics. The partial photodissociation cross-sections from all their vibrational levels towards the ten ^3Σ^+ and the six ^3Π superior states are calculated, from which the corresponding radiative stabilization cross-sections are then inferred. The rate constant for both processes is estimated in the range of temperature and of radiative energy distribution found in planetary nebulae. It is shown that the vibrational dependence of the radiative stabilization cross-section, usually neglected in the estimation of the rate constant, has a significant impact at low temperature.
Physical Chemistry Chemical Physics, 2011
We numerically implement quantum algorithms in hyperfine levels of ultracold polar molecules. Log... more We numerically implement quantum algorithms in hyperfine levels of ultracold polar molecules. Logical operations are driven by pulses optimized by optimal control theory. All implementations take place in the lowest two rotational levels of the ground vibrational state of the ground (1)Σ(+) electronic state, exploiting the richness of the hyperfine energy structure and state mixing in static external fields. We show that it is possible to realize high fidelity complex logical operations with microsecond pulses. The possibility to run algorithms implemented on two interacting molecules is also demonstrated. (41)K(85)Rb and (41)K(87)Rb molecules are considered for the numerical simulations but the results are general and can be extended to other species.
Theoretica Chimica Acta, Jan 1, 2012
... jlievin@ulb.ac.be 1 Not to be confused with the Atoms In Molecules (AIM) approach of the late... more ... jlievin@ulb.ac.be 1 Not to be confused with the Atoms In Molecules (AIM) approach of the late Richard Bader [6]. 123 Theor Chem Acc (2012) 131:1254 DOI10.1007/s00214-012-1254-3 Page 2. effects [71], the characterization ...
Physical Chemistry Chemical Physics, Nov 14, 2011
We numerically implement quantum algorithms in hyperfine levels of ultracold polar molecules. Log... more We numerically implement quantum algorithms in hyperfine levels of ultracold polar molecules. Logical operations are driven by pulses optimized by optimal control theory. All implementations take place in the lowest two rotational levels of the ground vibrational state of the ground (1)Σ(+) electronic state, exploiting the richness of the hyperfine energy structure and state mixing in static external fields. We show that it is possible to realize high fidelity complex logical operations with microsecond pulses. The possibility to run algorithms implemented on two interacting molecules is also demonstrated. (41)K(85)Rb and (41)K(87)Rb molecules are considered for the numerical simulations but the results are general and can be extended to other species.