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Physics Seminar

Overcoming the macroscopic 'Heisenberg limit' in topological photonics

Speaker: Prof Kosmas Tsakmakides (National and Kapodistrian University of Athens)
Date: Wednesday 2 June 2021
Time: 15:00
Venue: Zoom

Recounting how Heisenberg intuitively firstly conceived his famous time-energy quantum uncertainty principle (ΔΕΔt ≥ ħ/2), Max Born, his advisor at the time, recounts that it was inspired from the ‘complementarity principle’ of classical wave optics, which for non-propagating (standing or localized) waves takes on a particularly simple form: ΔωΔt = 1, where Δω is the bandwidth over which wave storage (localization) occurs, and Δt is the storage time. This product, sometimes known as the ‘time-bandwidth limit’, has until recently never been violated, not only in the quantum but also in the classical (non-quantum) regime, in any linear, time-invariant (LTI) structure, and it remains a fundamental challenge in classical wave physics and engineering to conceive devices overcoming it, not least because that would allow for storing broadband waves (large Δω’s) for long times (large Δt’s). Recent theoretical and experimental studies have suggested that such a feat might actually be possible in terminated unidirectional ('one-way') waveguides, or in topological ‘rainbow trapping’ devices, overturning much of conventional wisdom. In the talk, I shall concisely review these recent and ongoing developments, explaining how and why this limit could actually be overcome, leading to classical devices operating either above (ΔωΔt > 1) or below (ΔωΔt < 1) the limit. We shall also emphasize a range of exciting - hitherto considered 'unsolvable' - problems and applications that such a feat enables, and will review state-of-art corroborating experiments and topological schemes, which do not just overcome the limit but actually 'enforce' - in a mathematical/topological manner - its violation.

Bio: Dr Tsakmakidis obtained the Diploma degree in Electrical & Computer Engineering from the Aristotle University of Thessaloniki, Greece (2002), the Master of Research (MRes, summa cum laude) in EE, University of Surrey, UK (2003), and the Doctorate degree (PhD) in Applied Physics and Engineering (IoP PhD thesis prize in the UK), University of Surrey (2009).
During 2008-2013, he held a 5-year Royal Academy of Engineering/EPSRC research fellowship, first at the University of Surrey (2008-2010), and then at Imperial College London (2011-2013). He subsequently worked as a senior postdoctoral research fellow at the University of California, Berkeley, USA (2014-2015), as a Eugen Lommel postdoctoral fellow at the Max Planck – University of Ottawa Center for Extreme and Quantum Photonics & the Department of Physics, University of Ottawa, Canada (2015-2016), and as an EPFL Fellow at the Bioengineering Department, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland (2017-2018).
For his work, he has received young-scientist awards by, among others, the Royal Academy of Engineering (first-equal in the UK), the Institute of Physics (best PhD thesis), the UK Parliament (runner-up / 2nd place), and the University of Surrey (best Faculty young researcher). Since February 2018, he works as an assistant professor in the Section of Condensed Matter Physics, Department of Physics, National and Kapodistrian University of Athens, Greece.