The PhD-project Reinier van der Meer performed, was within the recently started Adapted Quantum Optics (AQO) group, led by professor Pepijn Pinkse. His high-tech experimental work offered new insights into developments in single-photon sources, and in interferometers for quantum photonics systems. ‘We have performed first-ever quantum experiments with a promising newly integrated commercial photonic platform,’ Reinier says.
A state-of-the-art photonic processor, together with a new multiphoton setup, formed the heart of all experiments within his thesis. ‘We collaborated closely with UT spin-off company Quix Quantum BV,’ Reinier says. ‘I helped characterise and test their silicon-nitride based integrated quantum-optical platform in our lab. After that, I used their quantum processor to study interesting physics in advanced multiphoton experiments.’
Single-photon sources
A missing piece to do multiphoton experiments was a reliable source that could generate many indistinguishable photons simultaneously. The traditional workhorse of quantum optics to realize this is a technique called: spontaneous parametric down-conversion (SPDC).
‘Here, however, nonlinear crystals are used,’ Reinier explains. ‘In cooperating with experts of the University of Paderborn, we were able to show the suitability of selected nonlinear crystals for our experiments, and for proposed noisy intermediate-scale quantum experiments. We have also built a 4-photon version of such a setup ourselves. The photon quality of our source is sufficient to allow us to scale up to 11-photons experiments. Which is more than sufficient for our initial two- and three-photon experiments.’
Experiments and collaborations
Once the setup was ready and the photonic processor available, Reinier was happy to make the transition towards multiphoton experiments during his PhD-project.
‘For me, studying physics is the exciting part of my PhD. We started working on a counter-intuitive prediction from the 1980s on wave propagation through disordered media. We did not only show proof of this prediction, but we also implicitly showed that this type of physics can be studied on integrated photonics.’
While working with this hardware, the question arose about how to still certify experiments when both the network and the number of indistinguishable photons are enlarged. ‘Such experiments are no longer simulable on classical computers,’ Reinier explains. ‘For this, we introduced and experimentally implemented, a one-sided device-independent photonic indistinguishability witness. The big advantage of our method is that it is robust against experimental imperfections and that it works in situ.’
Finally, a collaboration was started with Freie Universität Berlin, to study quantum thermodynamics. ‘We demonstrated the physical mechanism of how a pure quantum state thermalizes in a closed system. This experiment is a good example of a simulation on quantum hardware.’
MESA+
Reinier started his bachelor's study in Twente in 2011 already. ‘The atmosphere is friendly, which contributed to my decision to stay and do a PhD at MESA+. ’ he says. ‘During my time at the University of Twente and MESA+, the optics groups closely collaborated in the applied nanophotonics cluster: there is a monthly meeting where we discuss our research and share expertise and facilities. The people are helpful: during my PhD, I never came across a closed-door.’
Future
His future career Reinier sees in R&D, in an optics related company in the Netherlands. ‘Although I enjoy doing research, I have come to realize that I do not want to become a professor,’ he says. ‘I aim for an interesting R&D position in which my expertise in optics can be helpful in innovation technologies.’