Hybrid Quantum Cryptography from Communication Complexity

We introduce an explicit construction for a key distribution protocol in the Quantum Computational Timelock (QCT) security model, where one assumes that computationally secure encryption may only be broken after a time much longer than the coherence time of available quantum memories. Taking advantage of the QCT assumptions, we build a key distribution protocol called HM-QCT from the Hidden Matching problem for which there exists an exponential gap in one-way communication complexity between classical and quantum strategies. We establish that the security of HM-QCT against arbitrary i.i.d. attacks can be reduced to the difficulty of solving the underlying Hidden Matching problem with classical information. Legitimate users, on the other hand, can use quantum communication, which gives them the possibility of sending multiple copies of the same quantum state while retaining an information advantage. This leads to an everlasting secure key distribution scheme over $n$ bosonic modes. Such a level of security is unattainable with purely classical techniques. Remarkably, the scheme remains secure with up to $\mathcal{O}\big( \frac{\sqrt{n}}{\log(n)}\big)$ input photons for each channel use, extending the functionalities and potentially outperforming QKD rates by several orders of magnitudes.Comment: 25 pages, 5 figure

Optimal Control Methods for Quantum Batteries

We investigate the optimal charging processes for several models of quantum batteries, finding how to maximize the energy stored in a given battery with a finite-time modulation of a set of external fields. We approach the problem using advanced tools of optimal control theory, highlighting the universality of some features of the optimal solutions, for instance the emergence of the well-known Bang-Bang behavior of the time-dependent external fields. The technique presented here is general, and we apply it to specific cases in which the energy is both pumped into the battery by external forces (direct charging) or transferred into it from an external charger (mediated charging). In this article we focus on particular systems that consist of coupled qubits and harmonic oscillators, for which the optimal charging problem can be explicitly solved using a combined analytical-numerical approach based on our optimal control techniques. However, our approach can be applied to more complex setups, thus fostering the study of many-body effects in the charging process.Comment: 17 pages, 5 figure

Experimental vulnerability analysis of QKD based on attack ratings

Abstract Inspired by the methodology used for classical cryptographic hardware, we consider the use of attack ratings in the context of QKD security evaluation. To illustrate the relevance of this approach, we conduct an experimental vulnerability assessment of CV-QKD against saturation attacks, for two different attack strategies. The first strategy relies on inducing detector saturation by performing a large coherent displacement. This strategy is experimentally challenging and therefore translates into a high attack rating. We also propose and experimentally demonstrate a second attack strategy that simply consists in saturating the detector with an external laser. The low rating we obtain indicates that this attack constitutes a primary threat for practical CV-QKD systems. These results highlight the benefits of combining theoretical security considerations with vulnerability analysis based on attack ratings, in order to guide the design and engineering of practical QKD systems towards the highest possible security standards

Sistemi silvoarabili mediterranei: nuove esperienze in campo al Centro di Ricerche Agro-ambientali“Enrico Avanzi” di Pisa

L’agroselvicoltura, ovvero la deliberata associazione di colture arboree, erbacee e/o animali nel medesimo appez- zamento, è stata proposta come “nuovo sistema colturale” in grado di coniugare l’aumento di produtività dell’agricoltura in un’otica di maggiore eco-suficienza. Tra i diversi modelli colturali ascrivibili ai sistemi agro- silvopastorali o agrosilvicoli, i sistemi silvoarabili, che prevedono la coltivazione di colture erbacee di pieno cam- po in consociazione con colture arboree, garantiscono una serie di benefici direti: (i) la diversificazione delle col - ture, (ii) la riduzione del rischio di erosione del suolo dall’acqua e dal vento, (iii) l’aumento della percentuale di sostanza organica nel suolo, e (iv) la riduzione del rischio di lisciviazione dei nitrati. D’altro canto, la consociazio - ne di colture erbacee e alberi fuori-foresta determina la riduzione della superficie arabile complessiva e la compe- tizione per le risorse (nutrienti, luce ed acqua) tra alberi e strato erbaceo. Al fine di approfondire le conoscenze su questi particolari sistemi colturali, presso il Centro di Ricerche Agro-ambientali “Enrico Avanzi” dell’Universi - tà di Pisa sono in corso di implementazione due sperimentazioni di pineo campo. La prima prova è un sistema agro-silvo-pastorale che prevede la coltivazione di specie erbacee da granella (cereali autunno-vernini e legumi- nose) e prati-pascolo in rotazione, nel tempo e nello spazio, in consociazione con filari policiclici di pioppi ( Popu- lus spp.) e farnie (Qercus robur L.). I sistemi verranno implementati con due diverse densità di impianto: i) 60 piante per etaro, in cui i filari verranno posti in prossimità dell’afossatura di ogni appezzamento, e ii) 100 piante per etaro, in cui i filari di soli pioppi verranno ripetuti anche lungo la bisetrice del campo. La prova prevede il confronto dei servizi ecosistemici generati dai due sistemi silvoarabili con: i) un sistema arabile privo di alberatu- re, e ii) un sistema di arboricoltura ad alta densità. Nella seconda prova un campo parcellare silvoarabile, compo - sto da: erba mazzolina (Dactylis glomerata L.), erba medica (Medicago sativa L.), panico (Panicum virgatum L.) e sulla (Hedysarum coronarium L.) in consociazione con filari di pioppo a taglio ravvicinato, short-rotation coppice (SRC), a bassa densità (0.5 m di distanza tra gli alberi e 13.5 metri tra le file), verrà messo a confronto con: (i) una prova parcellare di SRC con impianto 0.5 m × 2.7 m, e (ii) un campo parcellare con le medesime colture erbacee prive di copertura arborea. L’obietivo della prova è valutare il grado di produtività e sostenibilità dei diversi si- stemi con particolare atenzione al ciclo del carbonio e al ciclo dei nutrienti

Optimal Methods for Quantum Batteries

In this thesis we will focus on the study of the so-called ‘‘Quantum Batteries’’, i.e. quantum mechanical systems for energy storage, where quantum effects can be used to obtain more efficient and faster charging processes with respect to classical systems. We present a systematic analysis of several models of Quantum Batteries charging processes, involving two-level systems and quantum harmonic oscillators. In order to find the best charging processes for our Quantum Batteries, we will use some features of Quantum Control Theory, that studies how a quantum state can be guided into a new chosen state of the Hilbert space of the system and how we can make use of this ability to control our system in order to reach a given objective

Hybrid Quantum Cryptography from Communication Complexity

We introduce an explicit construction for a key distribution protocol in the Quantum Computational Timelock (QCT) security model, where one assumes that computationally secure encryption may only be broken after a time much longer than the coherence time of available quantum memories. Taking advantage of the QCT assumptions, we build a key distribution protocol called HM-QCT from the Hidden Matching problem for which there exists an exponential gap in one-way communication complexity between classical and quantum strategies. We establish that the security of HM-QCT against arbitrary i.i.d. attacks can be reduced to the difficulty of solving the underlying Hidden Matching problem with classical information. Legitimate users, on the other hand, can use quantum communication, which gives them the possibility of sending multiple copies of the same quantum state while retaining an information advantage. This leads to an everlasting secure key distribution scheme over n bosonic modes. Such a level of security is unattainable with purely classical techniques. Remarkably, the scheme remains secure with up to O √ n log(n) input photons for each channel use, extending the functionalities and potentially outperforming QKD rates by several orders of magnitudes

An overview on long-term agro-ecosystem experiments: Present situation and future potential

Modern Long Term Agricultural experiments (LTAE) have a long history initiated when modern agricultural science was just at its beginning. After about 180 years from the start of the first of the classical Rothamsted experiments in 1843, these experiments still maintains a consistent appeal for researchers and the interest on LTAEs is growing, as shown by the increasing number of papers dealing with long-term effect of agricultural practices, frequently considering topics, such as sustainability, environmental quality, species-adaptation impacts, that were never envisioned by the founders of classical LTAEs. However, these experiments have numerous constraints and weakness that have to be clearly understood and evaluated when using the data, especially for up-scaling or modelling purposes.Nevertheless, in our vision, the strengths and the opportunities of LTAEs are still overwhelming, particularly if connected in networks allowing a standardisation of procedures and facilitating the access to data and to the experiments of researchers external to the institution hosting the LTA

Economic and environmental impact of input reduction in biennal rotations

In the past few decades there has been an increasing awareness concerning damage inflicted on the environment by economic activities. Thus decision-making procedures have been developed which are capable of taking into account the externalities resulting from human activities including agriculture. It is, however, very difficult to make an objective evaluation of externalities. The Authors propose a method, based on linear programming, which aims at isolating and limiting the subjectivity of evaluation, and provides a series of alternatives minimising chemical input. So a set of Pareto-efficient solutions rater than a subjective optimal one is provided for each gross margin level. The Authors subsequentely attempt to identify the best Pareto-efficient solution