Giuseppe Vitagliano

Entanglement is the most distinctive feature of quantum theory, but in large systems it is hard to characterize and harder still to observe, because single particles often cannot be addressed individually and only a few collective quantities can be measured. I develop criteria that certify and quantify entanglement, including how many particles share it and in how many dimensions, from data that experiments can actually access: collective spin moments, covariance matrices, randomized measurements. Behind these criteria lies the geometry of the set of quantum states, which I also study for its own sake.

Key papers

• Spin squeezing inequalities for arbitrary spin PRL 2011
• Entanglement between two spatially separated atomic modes Science 2018
• Entanglement certification from theory to experiment Nat. Rev. Phys. 2019
• Experimental certification of high-dimensional entanglement with randomized measurements PRL 2025

Uncertainty relations are among the deepest statements of quantum theory, and also remarkably practical tools. I use them to derive entanglement criteria from the variances of collective observables, which is the idea behind spin squeezing. I also study the opposite direction: how entanglement allows sensors and clocks to beat classical limits of precision, as quantified by the quantum Fisher information, including the case where several parameters have to be estimated at once.

Key papers

• Uncertainty relations between quantum Fisher information and entanglement monotones PRL 2026
• Characterizing resources for multiparameter estimation of SU(2) and SU(1,1) unitaries Quantum 2026
• Number-phase uncertainty relations and bipartite entanglement detection in spin ensembles Quantum 2023
• The uncertainty geometry of finite-dimensional position and momentum arXiv 2026

The first question I worked on, in my Bachelor’s thesis, was whether general relativity allows closed timelike curves. Time and causality have stayed with me since. I work on temporal quantum correlations: tests of macroscopic realism in the spirit of Leggett and Garg, in which a single system measured at successive times shows correlations that no macrorealist model can explain, and what such sequences of measurements reveal about hidden memory, the dimension of an unobserved environment and the precision of clocks. In Vienna I helped conceive and write the proposal for the Young Independent Research Group “Emergence of causal order in quantum theory and beyond”, where I then co-led the research line on temporal correlations.

Key papers

• Quantum non-demolition measurement enables macroscopic Leggett–Garg tests PRL 2015
• Ticking-clock performance enhanced by nonclassical temporal correlations PR Research 2021
• Leggett–Garg macrorealism and temporal correlations PRA 2023, invited perspective
• Witnessing environment dimension through temporal correlations Quantum 2024

Landauer’s principle limits the cost of erasing information, and the third law of thermodynamics says that absolute zero cannot be reached with finite resources. What these limits mean for quantum systems is still being clarified. I study what it costs, in energy, time and control complexity, to cool a quantum system or to create correlations between its parts. I also study how entanglement appears in thermal and out-of-equilibrium many-body systems such as one-dimensional Bose gases, where thermal machines made of quantum fields can be realized with ultracold atoms.

Key papers

• Landauer vs. Nernst: What is the true cost of cooling a quantum system? PRX Quantum 2023
• Thermodynamically optimal creation of correlations J. Phys. A 2019
• Quantum field thermal machines PRX Quantum 2021
• Thermal entanglement and out-of-equilibrium thermodynamics in 1D Bose gases arXiv 2026