Entanglement, loss, and quantumness: When balanced beam splitters are best

Abstract: Entanglement generation by beam splitters lies at the heart of quantum optics. Yet, the conjecture that maximal entanglement for any state interfered with the vacuum is generated by beam splitters with equal reflection and transmission probabilities has remained unproven for almost two decades, despite overwhelming positive evidence [1]. I will report on our recent proof of this conjecture that led to monotonicity and convexity properties for quantum states undergoing photon loss [2]. Because of the interplay between information theoretic concepts such as entropy and physical considerations such as quantum system design, noise, and loss, our results have numerous ramifications in development of applications and advancing our understanding of quantum physics [3]. They extend to measures of similarity between states, yield to new inequalities for quasiprobability distributions and prove the conjecture in [4] that the quadrature coherence scale always stops certifying nonclassicality at 50% <a href="http://loss.

[1]” target=”_blank” title=”loss.

[1]”>loss.

[1] Asboth et al. Phy. Rev. Lett. 94 (17), 173602 (2005)

[2] Lupu-Gladstein et al. Arxiv:2411.03423 (2024)

[3] Hertz et al. Arxiv:2501.02047 (2025)

[4] Hertz et al. Phys. Rev. A 110, 012408 (2024)
.

Co-sponsored by: Prof. Nicolas Quesada

Speaker(s): Anaelle Hertz

J. Armand Bombardier J-1035/J-2074, Polytechnique Montréal, Montréal, Quebec, Canada, H3T 1J4