Seminar: Nicole Yunger Halpern (NIST, QuICS, University of Maryland); Wed 1st December

01 December 2021, 4pm (time TBC)
Location: MS Teams online seminar

Quasiprobability distributions resemble probability distributions but can contain negative and imaginary values. Such distributions represent quantum states as probability distributions over phase space represent states in classical statistical mechanics. Many quasiprobabilities exist, the most famous being the Wigner function. Among the least famous ranks the Kirkwood-Dirac distribution, discovered during the early 1900s and then forgotten. But the Kirkwood-Dirac distribution has been enjoying a renaissance recently: Applications range from quantum chaos to tomography, metrology, foundations, and thermodynamics. I will introduce the Kirkwood-Dirac distribution and illustrate its usefulness in metrology: The quasiprobability can be used to prove that operators’ noncommmutation—a nonclassical phenomenon—underlies a protocol’s effectiveness in phase estimation. I aim to convince you that the Kirkwood- Dirac distribution is the best little quasiprobability you’d never heard of.

1) Arvidsson-Shukur, NYH, Lepage, Lasek, Barnes, and Lloyd, Nat. Comms. 11, 3775 (2020).
2) Arvidsson-Shukur, Drori-Chevalier, and NYH, J. Phys. A 54, 284001 (2021).
3) Lupu-Gladstein, Yilmaz, Arvidsson-Shukur, Brodutch, Pang, Steinberg, and NYH (in prep).
4) NYH, Swingle, and Dressel, Phys. Rev. A 97, 042105 (2018).

Seminar: Tijs Karman (Radboud University); Wed 3 November (3pm tbc)

Location: MS Teams

Shielding ultracold molecules with microwaves

Ultracold molecules are used for precision measurements, to explore chemistry in a coherent quantum mechanical regime, and applications in quantum technologies. Realizing these wide-ranging applications will require control of interactions between molecules.

In this talk, I will discuss how we can use microwaves to engineer repulsive long-range interactions between ultracold polar molecules [1].
The repulsive interactions prevent molecules from coming close together and thereby suppresses various loss mechanisms. At the same time, “microwave shielding” leads to large elastic cross sections required for thermalization and evaporative cooling — an elusive milestone in the field.

I will also discuss the first experimental realization of microwave shielding using cold CaF molecules trapped in optical tweezers [2], demonstrating a factor of six suppression of the inelastic loss.

[1] Phys. Rev. Lett. 121, 163401 (2018)
[2] Science 373, 779 (2021)

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We are a Research Cluster of the School of Mathematics and Physics at Queen’s University Belfast in Northern Ireland. Our research interests are focused primarily on computational and theoretical physics.

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