A portable cosmic ray detector for school education

This article describes the design, assembly and characterization of a portable cosmic ray detector, developed by the INSULAB group and suitable for teaching activities aimed at high school students. It consists of a compact aluminum suitcase containing three plastic scintillator modules coupled to photomultipliers, readout by a custom compact electronics chain and powered by a power bank. The modules operate in coincidence and the system records the arrival time of each particle and the time over threshold of the signal of each scintillator module. The data are acquired and processed by a Raspberry PI connected to a touch screen display for online monitoring. The procedure implemented for the determination of the detector efficiency is reported, along with the results of the measurements of the cosmic ray rate as a function of the altitude and the zenith angle, performed in the laboratory and in different locations outdoors.

Experimental Demonstration of Fine-Grained Steering Inequality of Two-Qubit Mixed States

Quantum steering, as a cornerstone of quantum information, is usually used to witness the quantum correlation of bipartite and multi-partite states. Here, we experimentally demonstrate the quantum steering inequality of two-qubit mixed states based on the fine-grained uncertainty relation. Our experimental results show that the steering inequality has potent sensitivity to Werner states and Bell diagonal states. The steering strategy exhibits a strong ability to identify that Werner states are steerable when the decoherence coefficient a>12. Compared to the steering inequality obtained by another stratagem, the steering witness criteria of mixed states based on the fine-grained uncertainty relation demonstrated in our experiment has better precision and accuracy. Moreover, the detection efficiency in our measurement setup is only required to be 50% to close the detection loophole, which means our approach needs less detector efficiency to certificate the steerability of mixed states.

Electron mobility dependence on neutron irradiation fluence in heavily irradiated silicon

An increase of neutron irradiation fluence caused a decrease of Si radiation detector efficiency that was exceptionally well seen at 1017 neutron/cm2 fluence when the observed I–V characteristic of p-n junction under forward bias and under reverse bias became similar. Therefore the investigation of free carrier mobility could be a key experiment to understand the change of heavily irradiated silicon. The electron mobility was investigated by magnetoresistance means in microstrip silicon samples at temperature range T = 200–276 K. The analysis included the free carrier scattering by phonons, ionized impurities, dipoles and clusters and a contribution of each process was found by fitting the mobility dependence on temperature. The analysis of experimental data clearly demonstrated that the applied model did not explain the mobility in the samples irradiated to the highest fluence. Therefore a new concept of carrier transport is needed, and, as a conclusion, it could be stated that Si irradiated above 1016 cm–2 fluence (and up to 1020 cm–2) is a disordered material with the clusters.

Simulation of the Bell inequality violation based on quantum steering concept

Violation of Bell’s inequality in experiments shows that predictions of local realistic models disagree with those of quantum mechanics. However, despite the quantum mechanics formalism, there are debates on how does it happen in nature. In this paper by use of a model of polarizers that obeys the Malus’ law and quantum steering concept, i.e. superluminal influence of the states of entangled pairs to each other, simulation of phenomena is presented. The given model, as it is intended to be, is extremely simple without using mathematical formalism of quantum mechanics. However, the result completely agrees with prediction of quantum mechanics. Although it may seem trivial, this model can be applied to simulate the behavior of other not easy to analytically evaluate effects, such as deficiency of detectors and polarizers, different value of photons in each run and so on. For example, it is demonstrated, when detector efficiency is 83% the S factor of CHSH inequality will be 2, which completely agrees with famous detector efficiency limit calculated analytically. Also, it is shown in one-channel polarizers the polarization of absorbed photons, should change to the perpendicular of polarizer angle, at very end, to have perfect violation of the Bell inequality (2 $$\sqrt 2$$ 2 ) otherwise maximum violation will be limited to (1.5 $$\sqrt{2}$$ 2 ).