Physical Sciences Colloquia

Abstract: Demographic gaps in retention and attainment mean that certain groups of students, e.g. those of particular gender, socio-economic group or ethnicity or with a disability, are considerably less likely to continue in their study of physics. This contributes to the “leaky pipeline” whereby the percentage of students and workers in particular demographic groups declines further and further. Various factors have been hypothesised as contributing to these discrepancies in attainment and the talk will start by outlining these factors, including the possibility that other “hidden variables” might be at play, the impact of a lack of self-confidence and an absence of appropriate role models, and the possibility that something in our teaching or assessment might favour particular demographic groups.

The talk will then focus on research at the Open University into variation between demographic groups (in particular gender) in engagement with different types of assessed tasks and features within the tasks (Dawkins et al., 2017; Hedgeland et al, 2018) as well as describing some recent findings into variation in decision-making behaviours.

References

Dawkins, H., Hedgeland, H. & Jordan, S. (2017). The impact of scaffolding and question structure on the gender gap. Physical Review Physics Education Research, 13, 020117.

Hedgeland, H., Dawkins, H. & Jordan, S. (2018). Investigating male bias in multiple choice questions: Contrasting formative and summative settings. European Journal of Physics, 39(5), 055704.

Abstract: TBC

Abstract:

Mid-infrared light scatters much less than shorter wavelengths, allowing greatly enhanced penetration depths for optical imaging techniques such as optical coherence tomography (OCT). However, both detection and broadband sources in the mid-IR are technologically challenging. Interfering entangled photons in a nonlinear interferometer enables sensing with undetected photons making mid-IR detectors obsolete. Here we implement mid-infrared frequency-domain OCT based on ultra-broadband entangled photon pairs and demonstrate 10 μm axial and 20 μm lateral resolution imaging of strongly scattering ceramic and paint samples. Achieving high SNR with 6 orders of magnitude less probe light than would be necessary with conventional mid-IR OCT and vastly reduced technical complexity this outperforms approaches with classical light.

About the speaker:

Dr. Sven Ramelow is for more than 10 years involved in experimental research with single photons. After his studies of physics at Humboldt-University Berlin, he completed his PhD and first PostDoc in Prof. Anton Zeilinger’s group at the University of Vienna. Here he dedicated his research to a number of fundamental quantum experiments as well as application-motivated topics like quantum communication and quantum imaging. During his second PostDoc at Cornell University, USA in Prof. Alex Gaeta’s group he extended his expertise in integrated quantum optics and quantum frequency conversion. Since 2017 Dr. Ramelow is leading an Emmy-Noether research group at Humboldt-University Berlin experimentally working on integrated optics, quantum frequency conversion and SPDC-based imaging, spectroscopy and OCT with undetected mid-IR photons.

Recent publication highlights:

Inna Kwiatkovsky, Helen Chrzanowski, Ellen G. Avery, Hendrik Bartolomaeus, Sven Ramelow “Microscopy with undetected photons in the mid-infrared”, arXiv:2002.05960

Joshi, A. Farsi, S. Clemmen, S. Ramelow, A. L. Gaeta, “Frequency Multiplexing for Quasi-Deterministic Heralded Single-Photon Sources“, Nature Comm. 9, 847 (2018)

Clemmen, A. Farsi, S. Ramelow, A. L. Gaeta, “Ramsey interference with single photons“, Phys. Rev. Lett. 117, 223601 (2016)

Baretto Lemos, V. Borish, G. D. Cole, S. Ramelow, R. Lapkiewicz, A. Zeilinger, “Quantum Imaging with Undetected Photons”, Nature 512, 409 (2014)

Abstract: TBC

Abstract:

Pnictonium and pnictenium ions (cations of group 15 elements in the +5 and +3 oxidation states respectively) are promising candidates for transition metal free catalysis of organic transformations. There has recently been considerable progress in the exploitation of the phosphorus-based cations for a wide range of Lewis acid catalysed reactions.¹ As group 15 is descended, the Lewis acidity of the central atom increases, bringing scope for improved catalytic properties. However, investigation of the heavier antimony and bismuth analogues has been relatively limited. We have synthesised several families of antimony-based cations with both coordinating and non-coordinating anions, and are currently investigating their reactivity. Proof-of-concept catalytic activity has been established for a number of cations, with surprising reactivity also being observed in many cases.²

1         J. M. Bayne and D. W. Stephan, Chem. Soc. Rev., 2016, 45, 765–774.

2         O. Coughlin, T. Krämer and S. L. Benjamin, Dalton Trans., 2020, 49, 1726–1730.

Abstract: TBC