Intriguing quantum effects that result from entangled molecular rovibrational states are shown to provide a novel means for controlling both differential and total collision cross sections in identical particle diatom-diatom scattering. Computational results on elastic and inelastic scattering of para--H $_2$ and para--H $_2$ are presented, with the collision energy ranging from 400 cm $^{-1}$ to the ultracold regime. The experimental realization and possible extension to other systems are discussed.Intriguing quantum effects that result from entangled molecular rovibrational states are shown to provide a novel means for controlling both differential and total collision cross sections in identical particle diatom-diatom scattering. Computational results on elastic and inelastic scattering of para--H$_2$ and para--H$_2$ are presented, with the collision energy ranging from 400 cm$^{-1}$ to the ultracold regime. The experimental realization and possible extension to other systems are discussed.

Dec 18, 200214 citations

Coherent multichannel optical theorem: Quantum control of the total scattering cross section

Adrien Devolder, Timur V. Tscherbul, Paul W. Brumer

The optical theorem is a fundamental aspect of quantum scattering theory. Here, we generalize this theorem to the case where the incident scattering state is a superposition of internal states of the collision partners, introducing additional interference contributions and, e.g., providing a route to control the total integral cross section. As in its standard form, forward scattering plays an essential role in the multichannel optical theorem, but with interference terms being related to the inelastic forward scattering amplitudes between states in the initial superposition. Using the resultant control index, we show that extensive control is possible over ultracold collisions of oxygen molecules in their rovibrational ground states, and of $^{85}\mathrm{Rb}\text{\ensuremath{-}}^{85}\mathrm{Rb}$ collisions, promising systems for the experimental demonstration of the quantum interference control of the total scattering cross section.The optical theorem is a fundamental aspect of quantum scattering theory. Here, we generalize this theorem to the case where the incident scattering state is a superposition of internal states of the collision partners, introducing additional interference contributions and, e.g., providing a route to control the total integral cross section. As in its standard form, forward scattering plays an essential role in the multichannel optical theorem, but with interference terms being related to the inelastic forward scattering amplitudes between states in the initial superposition. Using the resultant control index, we show that extensive control is possible over ultracold collisions of oxygen molecules in their rovibrational ground states, and of $^{85}\mathrm{Rb}\text{\ensuremath{-}}^{85}\mathrm{Rb}$ collisions, promising systems for the experimental demonstration of the quantum interference control of the total scattering cross section.

Physical Review AMay 18, 20228 citations

Complete Quantum Coherent Control of Ultracold Molecular Collisions

Adrien Devolder, Paul W. Brumer, Timur V. Tscherbul

We show that quantum interference-based coherent control is a highly efficient tool for tuning ultracold molecular collision dynamics that is free from the limitations of commonly used methods that rely on external electromagnetic fields. By varying the relative populations and phases of initial coherent superpositions of degenerate molecular states, we demonstrate complete coherent control over integral scattering cross sections in the ultracold s-wave regime of both the initial and final collision channels. The proposed control methodology is applied to ultracold O_{2}+O_{2} collisions, showing extensive control over s-wave spin-exchange cross sections and product branching ratios over many orders of magnitude.We show that quantum interference-based coherent control is a highly efficient tool for tuning ultracold molecular collision dynamics that is free from the limitations of commonly used methods that rely on external electromagnetic fields. By varying the relative populations and phases of initial coherent superpositions of degenerate molecular states, we demonstrate complete coherent control over integral scattering cross sections in the ultracold s-wave regime of both the initial and final collision channels. The proposed control methodology is applied to ultracold O_{2}+O_{2} collisions, showing extensive control over s-wave spin-exchange cross sections and product branching ratios over many orders of magnitude.

arXiv:2012.10269Physical Review LettersApr 13, 202134 citations

Generalized multichannel optical theorem: Coherent control of the total scattering cross section

Adrien Devolder, Timur V. Tscherbul, Brumer Paul

The optical theorem is a fundamental aspect of quantum scattering theory. Here, we generalize this theorem to the case where the incident scattering state is a superposition of internal states of the collision partners, introducing additional interference contributions and, e.g., providing a route to control the total integral cross section. As in its standard form, forward scattering plays an essential role in the generalized optical theorem, but with interference terms being related to the inelastic forward scattering amplitudes between states in the initial superposition. Using the resultant control index, we show that extensive control is possible over ultracold collisions of oxygen molecules in their rovibrational ground states, and of 85Rb-85Rb collisions, promising systems for the first experimental demonstration of the quantum interference control of the total scattering cross section.The optical theorem is a fundamental aspect of quantum scattering theory. Here, we generalize this theorem to the case where the incident scattering state is a superposition of internal states of the collision partners, introducing additional interference contributions and, e.g., providing a route to control the total integral cross section. As in its standard form, forward scattering plays an essential role in the generalized optical theorem, but with interference terms being related to the inelastic forward scattering amplitudes between states in the initial superposition. Using the resultant control index, we show that extensive control is possible over ultracold collisions of oxygen molecules in their rovibrational ground states, and of 85Rb-85Rb collisions, promising systems for the first experimental demonstration of the quantum interference control of the total scattering cross section.

arXiv:2202.02198Feb 4, 20220 citations

Coherent control of reactive scattering at low temperatures: Signatures of quantum interference in the differential cross sections for F+ H2 and F+HD

Adrien Devolder, Timur V. Tscherbul, Paul W. Brumer

Fundamental entanglement related challenges have prevented quantum-interference-based control (i.e., coherent control) of collisional cross sections from being implemented in the laboratory. Here, differential cross sections for reactive scattering at low temperatures are shown to provide a unique opportunity to display such interference-based control by forming coherent superpositions of degenerate rotational states of reactant molecules $|jm\ensuremath{\rangle}$ with different $m$ . In particular, we identify and quantify a unique signature of coherent control in reactive scattering with applications to $\mathrm{F}+ {\mathrm{H}}_{2}\ensuremath{\rightarrow}$ H $+\mathrm{HF}$ and HF $+$ D $\ensuremath{\leftarrow}$ F $+\mathrm{HD} \ensuremath{\rightarrow}\mathrm{HD} +$ F at $11\phantom{\rule{4pt}{0ex}}\mathrm{K}$ . Control is shown to be extensive.Fundamental entanglement related challenges have prevented quantum-interference-based control (i.e., coherent control) of collisional cross sections from being implemented in the laboratory. Here, differential cross sections for reactive scattering at low temperatures are shown to provide a unique opportunity to display such interference-based control by forming coherent superpositions of degenerate rotational states of reactant molecules $|jm\ensuremath{\rangle}$ with different $m$. In particular, we identify and quantify a unique signature of coherent control in reactive scattering with applications to $\mathrm{F}+ {\mathrm{H}}_{2}\ensuremath{\rightarrow}$ H $+\mathrm{HF}$ and HF $+$ D $\ensuremath{\leftarrow}$ F $+\mathrm{HD} \ensuremath{\rightarrow}\mathrm{HD} +$ F at $11\phantom{\rule{4pt}{0ex}}\mathrm{K}$. Control is shown to be extensive.

arXiv:2007.11454Physical Review ASep 28, 202015 citations

Quantum-Controlled Collisions of H2 Molecules

Nandini Mukherjee

The amount of information that can be obtained from a scattering experiment depends upon the precision with which the quantum states are defined in the incoming channel. By precisely defining the incoming states and measuring the outgoing states in a scattering experiment, we set up the boundary condition for experimentally solving the Schrödinger equation. In this Perspective we discuss cold inelastic scattering experiments using the most theoretically tractable H 2 and its isotopologues as the target. We prepare the target in a precisely defined rovibrational ( v, j, m ) quantum state using a special coherent optical technique called the Stark-induced adiabatic Raman passage (SARP). v and j represent the quantum numbers of the vibrational and rotational energy levels, and m refers to the projection of the rotational angular momentum vector j on a suitable quantization axis in the laboratory frame. Selection of the m quantum numbers defines the alignment of the molecular frame, which is necessary to probe the anisotropic interactions. For us to achieve the collision temperature in the range of a few degrees Kelvin, we co-expand the colliding partners in a mixed supersonic beam that is collimated to define a direction for the collision velocity. When the bond axis is aligned with respect to a well-defined collision velocity, SARP achieves stereodynamic control at the quantum scale. Through various examples of rotationally inelastic cold scattering experiments, we show how SARP coherently controls the dynamics of anisotropic interactions by preparing quantum superpositions of the orientational m states within a single rovibrational ( v, j ) energy state. A partial wave analysis, which has been developed for the cold scattering experiments, shows dominance of a resonant orbital that leaves its mark in the scattering angular distribution. These highly controlled cold collision experiments at the single partial wave limit allow the most direct comparison with the results of theoretical computations, necessary for accurate modeling of the molecular interaction potential.The amount of information that can be obtained from a scattering experiment depends upon the precision with which the quantum states are defined in the incoming channel. By precisely defining the incoming states and measuring the outgoing states in a scattering experiment, we set up the boundary condition for experimentally solving the Schrödinger equation. In this Perspective we discuss cold inelastic scattering experiments using the most theoretically tractable H 2 and its isotopologues as the target. We prepare the target in a precisely defined rovibrational ( v, j, m ) quantum state using a special coherent optical technique called the Stark-induced adiabatic Raman passage (SARP). v and j represent the quantum numbers of the vibrational and rotational energy levels, and m refers to the projection of the rotational angular momentum vector j on a suitable quantization axis in the laboratory frame. Selection of the m quantum numbers defines the alignment of the molecular frame, which is necessary to probe the anisotropic interactions. For us to achieve the collision temperature in the range of a few degrees Kelvin, we co-expand the colliding partners in a mixed supersonic beam that is collimated to define a direction for the collision velocity. When the bond axis is aligned with respect to a well-defined collision velocity, SARP achieves stereodynamic control at the quantum scale. Through various examples of rotationally inelastic cold scattering experiments, we show how SARP coherently controls the dynamics of anisotropic interactions by preparing quantum superpositions of the orientational m states within a single rovibrational ( v, j ) energy state. A partial wave analysis, which has been developed for the cold scattering experiments, shows dominance of a resonant orbital that leaves its mark in the scattering angular distribution. These highly controlled cold collision experiments at the single partial wave limit allow the most direct comparison with the results of theoretical computations, necessary for accurate modeling of the molecular interaction potential.

The Journal of Physical Chemistry AJan 5, 202322 citations

_2

and para--H

_2

are presented, with the collision energy ranging from 400 cm

^{-1}

to the ultracold regime. The experimental realization and possible extension to other systems are discussed.

m

. In particular, we identify and quantify a unique signature of coherent control in reactive scattering with applications to $\mathrm{F}+ {\mathrm{H}}_{2}\ensuremath{\rightarrow}$ H

+\mathrm{HF}

and HF

+

D $\ensuremath{\leftarrow}$ F $+\mathrm{HD} \ensuremath{\rightarrow}\mathrm{HD} +$ F at

11\phantom{\rule{4pt}{0ex}}\mathrm{K}

. Control is shown to be extensive.