Quantum/Physics Joint Seminar Series - Francesco Anna Mele, Friday, June 20th at 1:30pm in EEB 132 & Zoom

Speaker: Francesco Anna Mele, Physics at the Scuola Normale Superiore Pisa, Italy

Talk Title: From Tomography of CV Systems to a New Measure of Non-Gaussianity: The Symplectic Rank

Series: Quantum/Physics Joint Seminar Series

Abstract: Quantum state tomography, aimed at deriving a classical description of an unknown state from measurement data, is a fundamental task in quantum physics. In parallel, non-Gaussianity serves as a crucial resource for quantum information processing in continuous-variable (CV) systems.In this work, we investigate the fundamental limits of quantum state tomography for CV systems, revealing a deep connection between the efficiency in tomography and the degree of non-Gaussianity. Specifically:

We first show that tomography of general non-Gaussian states is extremely inefficient;
In contrast, we demonstrate that tomography of Gaussian states is efficient. To accomplish this, we introduce new tools of independent interest: tight bounds on the trace distance between CV states in terms of the norm distance between their first moments and covariance matrices.


We then explore the intermediate regime, establishing that tomography becomes progressively harder as the level of non-Gaussianity increases.

The latter result naturally leads to the concept of symplectic rank: a novel non-Gaussianity monotone that satisfies remarkable operational and resource-theoretic properties. Mathematically, the symplectic rank of a pure state is the number of symplectic eigenvalues of the covariance matrix that are strictly larger than the ones of the vacuum. Importantly, the symplectic rank is non-increasing under post-selected Gaussian operations, leading to strictly stronger no-go theorems for Gaussian conversion than those previously known. 
The talk will be based on: https://arxiv.org/pdf/2405.01431, https://arxiv.org/pdf/2411.02368, and https://arxiv.org/pdf/2504.19319 .

Biography: Francesco Anna Mele was born in Italy in 1997. He received the B.Sc. and M.Sc. degrees in physics from the University of Pisa, Italy, in 2021, and the Diploma degree in physics from Scuola Normale Superiore of Pisa, Italy, in 2021. He is currently pursuing a Ph.D. in Physics at the Scuola Normale Superiore of Pisa, Italy, under the supervision of Vittorio Giovannetti and Ludovico Lami. He is currently visiting the California Institute of Technology (Caltech) until August 15. His research interests include all aspects of quantum information and computation.

Host: Quntao Zhuang, Eli Levenson-Falk, Jonathan Habif, Daniel Lidar, Kelly Luo,k Todd Brun, Tony Levi, Stephan Haas

More Info: https://usc.zoom.us/j/91779790215?pwd=ZlygfD3dO1htFllfQ0n8HyIaLNnYjL.1

More Information: Francesco Mele -June 20, 2025.pdf

Location: Hughes Aircraft Electrical Engineering Center (EEB) - 132

Audiences: Everyone Is Invited

Contact: Marilyn Poplawski

Event Link: https://usc.zoom.us/j/91779790215?pwd=ZlygfD3dO1htFllfQ0n8HyIaLNnYjL.1

This event is open to all eligible individuals. USC Viterbi operates all of its activities consistent with the University's Notice of Non-Discrimination. Eligibility is not determined based on race, sex, ethnicity, sexual orientation, or any other prohibited factor.

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