Freiburg 2024 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 36: Quantum Metrology and Interference

Q 36.7: Talk

Wednesday, March 13, 2024, 16:00–16:15, HS 3219

Reducing Schmidt mode cross-overlap inside SU(1,1) interferometers — •Dennis Scharwald and Polina Sharapova — Department of Physics, Paderborn University, Warburger Straße 100, D-33098 Paderborn, Germany

One of the central challenges in quantum metrology is improving the quality of interferometers, for example measured by their phase sensitivity. Classical interferometers operating with coherent light are bound in their sensitivity by the shot noise limit (SNL), while nonlinear SU(1,1) interferometers may surpass it and reach the Heisenberg scaling. [1]

In our recent work [2], we use the numerical approach of integro-differential equations for the description of the parametric down-conversion (PDC) process to show that using an appropriately shaped mirror makes it possible to easily surpass the SNL in an SU(1,1) interferometer (“compensated” setup). In this work, we aim to extend the discussion presented therein by analyzing the overlap of the Schmidt modes and show how cross-coupling between modes of the two PDC sections is eliminated in the compensated setup. As a consequence, this leads to an improvement of the quality of the interferometer visible from the supersensitivity at high parametric gain.

[1] M. Manceau et al., New J. Phys. 19, 013014 (2017)

[2] D. Scharwald et al., Phys. Rev. Res. 5, 043158 (2023)

Keywords: Nonlinear interferometry; Parametric down-conversion; PDC; Phase sensitivity; Schmidt modes