Talk by Prof. Nenad Kralj: Absorption-free detection of objects inside an optical cavity

Abstract

„Interaction-free measurements were originally conceived as thought experiments to elucidate the measurement problem in quantum mechanics, e.g. those by Renninger [1] and Dicke [2]. Elitzur and Vaidman [3] used the term to describe a scheme where the presence or absence of a perfectly absorbing object in one arm of an optical interferometer is inferred without a single photon being in its vicinity. After a brief overview of these different meanings and setups, I will show how a Fabry-Pérot cavity can be optimized to detect a semi-transparent object placed inside it, or confirm its absence, while avoiding absorption. In particular, contrary to the case of a perfect absorber, there are regimes where an undercoupled cavity is favorable [4]. Finally, I will discuss if and when such a dectection can be considered interaction-free in the sense of Elitzur and Vaidman.“

References

1. M. Renninger, “Messungen ohne störung des meßobjekts,” Z. Physik 158(4), 417–421 (1960).
2. 2. R. H. Dicke, “Interaction–free quantum measurements: A paradox?” Am. J. Phys. 49(10),
925–930 (1981).
3. A. C. Elitzur and L. Vaidman, “Quantum mechanical interaction-free measurements,” Found.
Phys. 23(7), 987–997 (1993).
4. V. Vujnović, N. Kralj, and M. Karuza, „Detection of a semitransparent object with no exchange
of quanta,“ Opt. Express 33, 1385-1393 (2025).
Guest talk on 05.03.2026 by
Prof. Nenad Kralj (University of Rijeka, Croatia)

The QuantumFrontiers’s former member Prof. Nenad Kralj (from University of Rijeka, Croatia) will give this talk at the HITec office-building, Callinstraße 36, 30167 Hannover and via Zoom: https://mpi-aei.zoom-x.de/j/62277413100?pwd=ETmzyKZSTazS0xGpa4NCUKNs6LvWul.1