442 research outputs found
Characterisation of multipartite entanglement beyond the single-copy paradigm
Full text linkEntanglement shared among multiple parties presents complex challenges for the characterisation of different types of entanglement. One of the most basic insights is the fact that some mixed states can feature entanglement across every possible bipartition of a multipartite system, yet can be biseparable, i.e., can be produced via a mixture of partially separable states. To distinguish biseparable states from those states that genuinely cannot be produced from mixing partially separable states, the term genuine multipartite entanglement was coined. The premise for this distinction is that only a single copy of the state is distributed and locally acted upon. However, advances in quantum technologies prompt the question of how this picture changes when multiple copies of the same state become locally accessible. In this talk I will discuss recent work [1] in which we show that multiple copies unlock genuine multipartite entanglement from partially separable states, even from undistillable ensembles, and we demonstrate that more than two copies can be required to observe this effect.
Our results show that a modern theory of entanglement in multipartite systems, which includes the potential to locally process multiple copies of distributed quantum states, exhibits a rich structure that goes beyond the convex structure of single copies. Indeed, based on our results, we present two conjectures about this structure: (i) the existence of a hierarchy of k-copy activatable states, for which k-1 copies remain biseparable, but k copies are GME, and (ii) the asymptotic collapse of the hierarchy of genuinely k-partite entangled states, i.e., that k copies of any biseparable but not partition-separable state become GME as k tends to infinity. In other words, we conjecture separability in multipartite systems to asymptotically collapse to the simple bipartite concept of separability in scenarios with unbounded numbers of copies, and we show that two copies are certainly not sufficient for reaching this simple limit, thus leaving the practical certification a rich problem to be studied.
If time permits, I will also give an overview of recent work [2] on the problem of distributing multiple copies of multipartite entangled states and how techniques from quantum estimation theory can aid in such tasks
[1] Hayata Yamasaki, Simon Morelli, Markus Miethlinger, Jessica Bavaresco, Nicolai Friis, and Marcus Huber, Activation of genuine multipartite entanglement: beyond the single-copy paradigm of entanglement characterisation, Quantum 6, 695 (2022) [arXiv:2106.01372]
[2] Simon Morelli, David Sauerwein, Michalis Skotiniotis, and Nicolai Friis, Metrology-assisted entanglement distribution in noisy quantum networks, Preprint: arXiv:2110.15627 [quant-ph] (2021
Motion generates entanglement
No full textWe demonstrate entanglement generation between mode pairs of a quantum field in a single, rigid cavity that moves nonuniformly in Minkowski space-time. The effect is sensitive to the initial state, the choice of the mode pair and bosonic versus fermionic statistics, and it can be stronger by orders of magnitude than the entanglement degradation between an inertial cavity and a nonuniformly moving cavity. Detailed results are given for massless scalar and spinor fields in (1+1) dimensions. By the equivalence principle, the results model entanglement generation by gravitational effects
Quantum gates and multipartite entanglement resonances realized by nonuniform cavity motion
No full textWe demonstrate the presence of genuine multipartite entanglement between the modes of quantum fields in nonuniformly moving cavities. The transformations generated by the cavity motion can be considered as multipartite quantum gates. We present two setups for which multimode entanglement can be generated for bosons and fermions. As a highlight we show that the genuine bosonic multipartite correlations can be resonantly enhanced. Our results provide fundamental insights into the structure of Bogoliubov transformations and suggest strong links between quantum information, quantum fields in curved spacetimes and gravitational analogues by way of the equivalence principle.</p
Relativistic Quantum Teleportation with Superconducting Circuits
No full textWe study the effects of relativistic motion on quantum teleportation and propose a realizable experiment where our results can be tested. We compute bounds on the optimal fidelity of teleportation when one of the observers undergoes nonuniform motion for a finite time. The upper bound to the optimal fidelity is degraded due to the observer's motion. However, we discuss how this degradation can be corrected. These effects are observable for experimental parameters that are within reach of cutting-edge superconducting technology
Austrian economics: a tale of lost opportunities
No full textThis is a, somewhat indirect, rejoinder to Boettke (2019, this volume, Chapter 1). Doing Austrian economics is low prestige: Austrian economics does not get published in high-prestige journals and Austrian economists are not employed by top universities. And yet, up until World War II Austrian economics was an important part of the international economics community. The author argues that Austrian economists made several theoretical innovations that could have placed them at the frontier of research in economics, and present a brief coun-terfactual history of a thriving Austrian economics based on those innovations. However, the actual history of the Austrian School is quite different. A par-ticularly decisive factor that has made Austrian economics a fringe movement was the rejection of formal methods in theory and empirics. The author argues that Austrian economics is basically dying out as a voice in the conversation of modern economists
Intuizione e conoscenza in Nicolai Hartmann (1911-1926). Sulle premesse dell'ontologia critica
No full textIntuition and Knowledge in Nicolai Hartmann (1911-1926). On the Premises of Critical Ontology. The author considers Nicolai Hartmann’s main points on the relationship between intuition and knowledge in his early and middle works (1911-1926). The author first shows how Hartmann’s critical ontology emerged as a reaction to the approach of the logical idealism of the Marburg School, against which Hartmann defends the existence of an irrational dimension of knowledge that legitimizes a minimum of metaphysics even in the gnoseological sphere. The author then focuses on the way in which Hartmann interprets the relationship between intuition and givenness, apriority, status of a priori principles, and understanding. Hartmann argues that intuition is not exclusively the same as empirical intuition, and that the problem of knowledge should no longer be considered in terms of the distinction between sensibility and understanding, but through the difference between a priori and a posteriori knowledge
Intuizione e conoscenza in Nicolai Hartmann (1911-1926). Sulle premesse dell'ontologia critica
No full textIntuition and Knowledge in Nicolai Hartmann (1911-1926). On the Premises of Critical Ontology. The author considers Nicolai Hartmann’s main points on the relationship between intuition and knowledge in his early and middle works (1911-1926). The author first shows how Hartmann’s critical ontology emerged as a reaction to the approach of the logical idealism of the Marburg School, against which Hartmann defends the existence of an irrational dimension of knowledge that legitimizes a minimum of metaphysics even in the gnoseological sphere. The author then focuses on the way in which Hartmann interprets the relationship between intuition and givenness, apriority, status of a priori principles, and understanding. Hartmann argues that intuition is not exclusively the same as empirical intuition, and that the problem of knowledge should no longer be considered in terms of the distinction between sensibility and understanding, but through the difference between a priori and a posteriori knowledge
Intuizione e conoscenza in Nicolai Hartmann (1911-1926). Sulle premesse dell'ontologia critica
No full textIntuition and Knowledge in Nicolai Hartmann (1911-1926). On the Premises of Critical Ontology. The author considers Nicolai Hartmann’s main points on the relationship between intuition and knowledge in his early and middle works (1911-1926). The author first shows how Hartmann’s critical ontology emerged as a reaction to the approach of the logical idealism of
the Marburg School, against which Hartmann defends the existence of an irrational dimension of knowledge that legitimizes a minimum of metaphysics even in the gnoseological sphere. The author then focuses on the way in which Hartmann interprets the relationship between intuition and givenness, apriority, status of a priori principles, and understanding. Hartmann
argues that intuition is not exclusively the same as empirical intuition, and that the problem of knowledge should no longer be considered in terms of the distinction between sensibility and understanding, but through the difference between a priori and a posteriori knowledge
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