Hybrid photonic circuits for fundamental quantum physics (HBNCIRQ)

Quantum mechanics is one of the most successful theories in physics, governing practically all processes in the microscopic world and even affecting many phenomena on a mesoscopic scale. It has countless applications in various fields and its predictions have been in excellent agreement with all experimental observations made throughout the last century. However, as all theories in physics it rests on a set of unprovable assumptions, the postulates, which have been formulated in accordance with experimental evidence. Conversely, only experiments can be used to validate or falsify these assumptions.

In a joint project together with our partners Robert Chapman and Rachel Grange at ETH Zurich, Switzerland and Tobias Vogl, TU Munich, Germany, we thrive to develop an advanced experimental platform to test two of the foundations of this successful theory. In particular we work with single-photon multi-path interferometers to experimentally test the postulates of the Born rule as well as the complex-number representation of quantum states. Our aim is to improve the accuracy of these tests by one order of magnitude over the state of the art. This will help to narrow the parameter space of generalised quantum theories.

Our experimental platform is a hybrid quantum system involving room-temperature single-photon emitters based on hexagonal boron nitride (hBN), quantum frequency conversion and lithium niobate-on-insulator (LNOI) waveguide interferometers, all integrated into a single photonic circuit. Developing this experimental platform is a challenge in itself, but promises several advantages, especially interferometric stability and high switching contrast in the LNOI waveguides as well as the controlled emission of pure single photons at room temperature without the need for bulky cryogenic equipment.

Researchers: Yigit Erarslan, Josef Hloušek, Robert Keil (PI)

Funding: FWF, 10.55776/PIN9593224, 2025 - 2028

 

 

News:

8 Menschen vor dem Institut lächeln in die Kamera
  • 11.11.2025 - Our kick-off event with our partners from Zurich and Munich took place in Innsbruck (see photo). Thanks everyone for this productive exchange at the start of the project! 
  • 01.10.2025 - Yigit Erarslan joins our team as a PhD student. Yigit will be working towards integrating the whole experiment at the UIBK lab, in close collaboration with our partners.
  • 14.11.2024 - As a precursor to this project, we have precisely measured the nonlinear response of one of our telecom-wavelength superconducting nanowire single photon detectors. It exhibited some interesting interplay of dead-time saturation and multi-photon absorption, which can be a systematic error source in the envisioned fundamental tests of quantum physics. We have published these results in APL Quantum.

 

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