arXiv subjects

Giuseppe Bianco

Publications and source records attributed to Giuseppe Bianco.

11 recordsLinked to original sources

arXiv2023

First results of the LARES 2 space experiment to test the general theory of relativity

The LAGEOS 3 (today LARES 2) space experiment was proposed in the eighties by the Physics Department and by the Center of Space Research (CSR) of the University of Texas (UT) at Austin and by the Italian Space Agency (ASI) to test and accurately measure frame-dragging, with the strong support of John Archibald Wheeler, director of the Center for Theoretical Physics of UT Austin. Frame-dragging is an intriguing phenomenon predicted by Einstein's theory of general relativity which has fundamental implications in high energy astrophysics and in the generation of gravitational waves by spinning black holes. LAGEOS 3 was reproposed in 2016 to the Italian Space Agency and to the European Space Agency as a technologically much improved version of LAGEOS 3 under the name LARES 2 (LAres RElativity Satellite 2) and then successfully launched in 2022 with the new launch vehicle VEGA C of ASI, ESA and AVIO. Today, after almost forty years since the original proposal, we report the first results of the LARES 2 space experiment to test general relativity. The results are in complete agreement with the predictions of Einstein's gravitational theory. Whereas previous results already confirmed the frame-dragging prediction, the conceptual relative simplicity of the LARES 2 experiment with respect to the previous tests with the LARES and LAGEOS satellites provides a significant advance in the field of tests of general relativity.

gr-qc↗

arXiv2019

Toxic Code Snippets on Stack Overflow

Online code clones are code fragments that are copied from software projects or online sources to Stack Overflow as examples. Due to an absence of a checking mechanism after the code has been copied to Stack Overflow, they can become toxic code snippets, e.g., they suffer from being outdated or violating the original software license. We present a study of online code clones on Stack Overflow and their toxicity by incorporating two developer surveys and a large-scale code clone detection. A survey of 201 high-reputation Stack Overflow answerers (33% response rate) showed that 131 participants (65%) have ever been notified of outdated code and 26 of them (20%) rarely or never fix the code. 138 answerers (69%) never check for licensing conflicts between their copied code snippets and Stack Overflow's CC BY-SA 3.0. A survey of 87 Stack Overflow visitors shows that they experienced several issues from Stack Overflow answers: mismatched solutions, outdated solutions, incorrect solutions, and buggy code. 85% of them are not aware of CC BY-SA 3.0 license enforced by Stack Overflow, and 66% never check for license conflicts when reusing code snippets. Our clone detection found online clone pairs between 72,365 Java code snippets on Stack Overflow and 111 open source projects in the curated Qualitas corpus. We analysed 2,289 non-trivial online clone candidates. Our investigation revealed strong evidence that 153 clones have been copied from a Qualitas project to Stack Overflow. We found 100 of them (66%) to be outdated, of which 10 were buggy and harmful for reuse. Furthermore, we found 214 code snippets that could potentially violate the license of their original software and appear 7,112 times in 2,427 GitHub projects.

cs.SE↗

arXiv2019

Sub-ns timing accuracy for satellite quantum communications

Satellite quantum communications have rapidly evolved in the past few years, culminating in the proposal, development, and deployment of satellite missions dedicated to quantum key distribution and the realization of fundamental tests of quantum mechanics in space. However, in comparison with the more mature technology based on fiber optics, several challenges are still open, such as the capability of detecting, with high temporal accuracy, single photons coming from orbiting terminals. Satellite laser ranging, commonly used to estimate satellite distance, could also be exploited to overcome this challenge. For example, high repetition rates and a low background noise can be obtained by determining the time-of-flight of faint laser pulses that are retro-reflected by geodynamics satellites and then detected on Earth at the single-photon level. Here we report an experiment with regard to achieving a temporal accuracy of approximately 230 ps in the detection of an optical signal of few photons per pulse reflected by satellites in medium Earth orbit, at a distance exceeding 7500 km, by using commercially available detectors. Lastly, the performance of the Matera Laser Ranging Observatory is evaluated in terms of the detection rate and the signal-to-noise ratio for satellite quantum communications.

quant-ph↗

arXiv2018

Towards Quantum Communication from Global Navigation Satellite System

Satellite-based quantum communication is an invaluable resource for the realization of a quantum network at the global scale. In this regard, the use of satellites well beyond the low Earth orbits gives the advantage of long communication time with a ground station. However, high-orbit satellites pose a great technological challenge due to the high diffraction losses of the optical channel, and the experimental investigation of such quantum channels is still lacking. Here, we report on the first experimental exchange of single photons from Global Navigation Satellite System at a slant distance of 20000 kilometers, by exploiting the retroreflector array mounted on GLONASS satellites. We also observed the predicted temporal spread of the reflected pulses due to the geometrical shape of array. Finally, we estimated the requirements needed for an active source on a satellite, aiming towards quantum communication from GNSS with state-of-the-art technology.

quant-ph↗

arXiv2017

Extending Wheeler's delayed-choice experiment to Space

Gedankenexperiments have consistently played a major role in the development of quantum theory. A paradigmatic example is Wheeler's delayed-choice experiment, a wave-particle duality test that cannot be fully understood using only classical concepts. Here, we implement Wheeler's idea along a satellite-ground interferometer which extends for thousands of kilometers in Space. We exploit temporal and polarization degrees of freedom of photons reflected by a fast moving satellite equipped with retro-reflecting mirrors. We observed the complementary wave-like or particle-like behaviors at the ground station by choosing the measurement apparatus while the photons are propagating from the satellite to the ground. Our results confirm quantum mechanical predictions, demonstrating the need of the dual wave-particle interpretation, at this unprecedented scale. Our work paves the way for novel applications of quantum mechanics in Space links involving multiple photon degrees of freedom.

quant-ph↗

arXiv2016

Interference at the Single Photon Level Along Satellite-Ground Channels

Quantum interference arising from superposition of states is a striking evidence of the validity of Quantum Mechanics, confirmed in many experiments and also exploited in applications. However, as for any scientific theory, Quantum Mechanics is valid within the limits in which it has been experimentally verified. In order to extend such limits, it is necessary to observe quantum interference in unexplored conditions such as moving terminals at large distance in Space. Here we experimentally demonstrate single photon interference at a ground station due to the coherent superposition of two temporal modes reflected by a rapidly moving satellite thousand kilometers away. The relative speed of the satellite induces a varying modulation in the interference pattern. The measurement of the satellite distance in real time by laser ranging allowed us to precisely predict the instantaneous value of the interference phase. We then observed the interference patterns with visibility up to $67\%$ with three different satellites and with path length up to 5000 km. Our results attest the viability of photon temporal modes for fundamental tests of Physics and Quantum Communications in Space.

quant-ph↗

arXiv2016

Experimental single photon exchange along a space link of 7000 km

Extending the single photon transmission distance is a basic requirement for the implementation of quantum communication on a global scale. In this work we report the single photon exchange from a medium Earth orbit satellite (MEO) at more than 7000 km of slanted distance to the ground station at the Matera Laser Ranging Observatory. The single photon transmitter was realized by exploiting the corner cube retro-reflectors mounted on the LAGEOS-2 satellite. Long duration of data collection is possible with such altitude, up to 43 minutes in a single passage. The mean number of photons per pulse (μsat) has been limited to 1 for 200 seconds, resulting in an average detection rate of 3.0 cps and a signal to noise ratio of 1.5. The feasibility of single photon exchange from MEO satellites paves the way to tests of Quantum Mechanics in moving frames and to global Quantum Information.

quant-ph↗

arXiv2014

Experimental Satellite Quantum Communications

Quantum Communications on planetary scale require complementary channels including ground and satellite links. The former have progressed up to commercial stage using fiber-cables, while for satellite links, the absence of terminals in orbit has impaired theirs development. However, the demonstration of the feasibility of such links is crucial for designing space payloads and to eventually enable the realization of protocols such as quantum-key-distribution (QKD) and quantum teleportation along satellite-to-ground or intersatellite links. We demonstrated the faithful transmission of qubits from space to ground by exploiting satellite corner cube retroreflectors acting as transmitter in orbit, obtaining a low error rate suitable for QKD. We also propose a two-way QKD protocol exploiting modulated retroreflectors that necessitates a minimal payload on satellite, thus facilitating the expansion of Space Quantum Communications.

quant-ph↗

arXiv2014

Analysis of self-overlap reveals trade-offs in plankton swimming trajectories

Movement is a fundamental behaviour of organisms that brings about beneficial encounters with resources and mates, but at the same time exposes the organism to dangerous encounters with predators. The movement patterns adopted by organisms should reflect a balance between these contrasting processes. This trade-off can be hypothesized as being evident in the behaviour of plankton, which inhabit a dilute 3D environment with few refuges or orienting landmarks. We present an analysis of the swimming path geometries based on a volumetric Monte Carlo sampling approach, which is particularly adept at revealing such trade-offs by measuring the self-overlap of the trajectories. Application of this method to experimentally measured trajectories reveals that swimming patterns in copepods are shaped to efficiently explore volumes at small scales, while achieving a large overlap at larger scales. Regularities in the observed trajectories make the transition between these two regimes always sharper than in randomized trajectories or as predicted by random walk theory. Thus real trajectories present a stronger separation between exploration for food and exposure to predators. The specific scale and features of this transition depend on species, gender, and local environmental conditions, pointing at adaptation to state and stage dependent evolutionary trade-offs.

q-bio.PE↗

arXiv2008

Space-QUEST: Experiments with quantum entanglement in space

The European Space Agency (ESA) has supported a range of studies in the field of quantum physics and quantum information science in space for several years, and consequently we have submitted the mission proposal Space-QUEST (Quantum Entanglement for Space Experiments) to the European Life and Physical Sciences in Space Program. We propose to perform space-to-ground quantum communication tests from the International Space Station (ISS). We present the proposed experiments in space as well as the design of a space based quantum communication payload.

quant-ph↗

arXiv2008

Experimental verification of the feasibility of a quantum channel between Space and Earth

Extending quantum communication to Space environments would enable to perform fundamental experiments on quantum physics as well as applications of quantum information at planetary and interplanetary scales. Here, we report the first experimental implementation of a scheme for single-photon exchange between a satellite and an Earth-based station. We built an experiment that mimics a single photon source on a satellite, exploiting the telescope at the Matera Laser Ranging Observatory of the Italian Space Agency to detect the transmitted photons. Weak laser pulses, emitted by the ground-based station, are directed towards a satellite equipped with cube-corner retroreflectors. These reflect a small portion of the pulse, with an average of less-than-one photon per pulse directed to our receiver, as required for the faint-pulse quantum communication. We were able to detect returns from satellite Ajisai, a low-earth orbit geodetic satellite, whose orbit has a perigee height of 1485 km.

quant-ph↗