Complete quantum coherent control of ultracold collisions
ORAL
Abstract
Most current control methods for ultracold atomic and molecular collisions are based on static (dc) and time-varying (ac) external electromagnetic fields. Unfortunately, they suffer several caveats, like the absence of magnetic (or electric) dipole moments for some molecules, the practical laboratory dc fields, or the perturbation of high-precision experiments.
Quantum coherent control is a promising approach free of these limitations and then complementary with the current methods. It is based on the coherent superposition of initial internal states, inducing interference of scattering amplitudes to a final state. Unfortunately, a large number of involved partial waves hamper the extent of control of integral cross-section (ICS). Therefore, ultracold temperatures are ideal conditions for coherent control.
We show that complete control of ICS is accessible when only a single partial wave is involved in both the incident and final collision channels (double s-wave regime). Destructive interference induces the vanishing of the ICS. With the example of spin-exchange scattering between O2 molecules, a huge control of ICS (10-4 to 105 Å2) and branching ratio (10-9 to 108) is demonstrated. Beyond the double s-wave regime, we demonstrated that one can completely control the contribution of one partial wave in ICS. A d-wave dominant scattering can be changed to an s-wave dominant scattering by tuning the relative phase of the initial superposition. Therefore, coherent control is also a powerful tool for tuning the partial wave expansion.
Quantum coherent control is a promising approach free of these limitations and then complementary with the current methods. It is based on the coherent superposition of initial internal states, inducing interference of scattering amplitudes to a final state. Unfortunately, a large number of involved partial waves hamper the extent of control of integral cross-section (ICS). Therefore, ultracold temperatures are ideal conditions for coherent control.
We show that complete control of ICS is accessible when only a single partial wave is involved in both the incident and final collision channels (double s-wave regime). Destructive interference induces the vanishing of the ICS. With the example of spin-exchange scattering between O2 molecules, a huge control of ICS (10-4 to 105 Å2) and branching ratio (10-9 to 108) is demonstrated. Beyond the double s-wave regime, we demonstrated that one can completely control the contribution of one partial wave in ICS. A d-wave dominant scattering can be changed to an s-wave dominant scattering by tuning the relative phase of the initial superposition. Therefore, coherent control is also a powerful tool for tuning the partial wave expansion.
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Publication: A. Devolder, P. Brumer and T. Tscherbul, "Complete quantum coherent control of ultracold molecular collisions" Phys. Rev. Lett.(submitted), arxiv: https://arxiv.org/abs/2012.10269
Presenters
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Adrien Devolder
Chemical Physics Theory Group, Department of Chemistry, and Center for Quantum Information and Quantum Control, University of Toronto
Authors
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Adrien Devolder
Chemical Physics Theory Group, Department of Chemistry, and Center for Quantum Information and Quantum Control, University of Toronto
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Paul Brumer
Chemical Physics Theory Group, Department of Chemistry, and Center for Quantum Information and Quantum Control, University of Toronto
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Timur Tscherbul
University of Nevada, Reno, Department of Physics, University of Nevada