In this project, we unearthed, pushed, and recharted the boundaries of the quantum world. On one hand, this shed new light on fundamental aspects of quantum theory, by unveiling its signatures in systems of increasing complexity. On the other hand, this led to novel blueprints for practical quantum technologies, able to operate in real world conditions. The project produced over 100 publications. Our research impacted not only on the scientific community – opening new directions in quantum science – but also on policymakers and general public – inspiring them through press releases, visual arts, poetry, and interventions at World Economic Forum meetings.
MAIN ACHIEVEMENTS
O1:
We developed fundamental contributions to the characterisation of quantum coherence and all forms of quantum correlations. We established general "monogamy" limitations on the shareability of such correlations. We developed efficient schemes to witness and estimate signatures of quantumness in systems of arbitrary dimension without the need for a complete tomographical reconstruction of the quantum state. We resolved the longstanding debate about the nature of entanglement between identical particles by showing that the latter is a consistent physical resource. These results were corroborated by experimental demonstrations with photonics, ultracold atoms, and nuclear magnetic resonance setups.
O2:
We determined the maximum achievable performance of continuous variable quantum teleportation and quantum cryptography schemes using Gaussian states and operations. We provided the first unconditional security proof for the multipartite cryptographic primitive known as quantum secret sharing. We discovered that to achieve secure quantum teleportation with fidelity above the so-called no-cloning threshold one needs to exploit steering, a type of quantum correlation stronger than entanglement. We demonstrated experimentally the creation and distribution of steering in multimode states of light, and determined the best use of limited resources (energy and entanglement) for quantum communication.
O3:
We determined optimal strategies for noisy quantum metrology in discrete and continuous variable systems. We demonstrate the role of entanglement versus more general quantum correlations in providing quantum-enhanced measurements. We determined the ultimate limits on quantum superresolution imaging in three dimensions and investigated applications to surface metrology, with impact on the manufacturing industry. We developed novel mathematical techniques to evaluate the figure of merit accounting for the achievable precision in the estimation of multiple physical parameters.
O4:
We contributed to the expeditious development of quantum thermodynamics, through a series of organised events, an edited book which is now regarded as the primary reference in the field, and a number of seminal publications. These include the determination of universal performance bounds for autonomous quantum refrigerators, the establishment of fundamental limitations on algorithmic cooling with Gaussian operations, a complete classification of Gaussian thermal operations, the quantification of work extraction in assisted scenarios, and the proposal of experimentally feasible schemes for non-destructive thermometry of ultra-cold gases with individual quantum probes.
O5:
We applied notions inspired by cybernetics to the study and manipulation of quantum coherence, deriving fundamental fluctuation relations akin to the second law of thermodynamics. We quantified the usefulness of quantum correlations in quantum feedback cooling schemes. We established fundamental “no-go” limitations on distillation of Gaussian resources. We provided universal bounds on the emergence of objectivity of observables in quantum Darwinism for systems of arbitrary complexity. Last but not least, we demonstrated that every convex quantum resource yields an operational advantage in discrimination tasks, thus establishing the universal value of quantumness.
