Quantum cryptography continues to be an area of significant research and educational interest. Here, a straightforward and reliable approach to both the experimental and theoretical aspects of quantum key distribution is presented, tailored for senior undergraduate students. Focusing on illustrating the essential concepts of the B92 protocol through a combination of optical experiments and custom-developed computational tools, this work offers a thorough exploration of quantum cryptography according to the principles of the B92 protocol.

A bstract: In a supersymmetry scenario with R-parity violation (RPV), neutralinos with GeV-scale mass, which are necessarily bino-like, are allowed by all constraints and can be produced in association with a baryon in B -meson decays via certain $$ \overline{U}\overline{D}\overline{D} $$ U ¯ D ¯ D ¯ operators. In this work, we investigate this scenario with two non-vanishing RPV couplings at the low-energy scale. With one RPV coupling governing the neutralino production rate and another determining its lifetime, this scenario can lead to observable signals with displaced-vertex signatures in the tracking volume of B -factories. To maximize the sensitivity to such signals, we develop a new partial-reconstruction technique that yields high efficiency and utilizes most of the decays of relatively heavy, long-lived particles, achieving much better sensitivity than standard full reconstruction. We consider potential background sources and devise selection criteria to suppress their event yields to very low levels. Using a parameterized model of the detector, we estimate in detail the displaced-vertex reconstruction efficiency as a function of neutralino lifetime and mass. For squark masses beyond the LHC limits, we calculate the signal sensitivity of Belle II, showing that the experiment can probe the RPV couplings well beyond the present bounds, obtained from searches for dinucleon decays, baryon-antibaryon oscillations, and B ⁺ → p + missing.

Quantum cryptography continues to be an area of significant research and educational interest. Here, a straightforward and reliable approach to both the experimental and theoretical aspects of quantum key distribution is presented, tailored for senior undergraduate students. Focusing on illustrating the essential concepts of the B92 protocol through a combination of optical experiments and custom-developed computational tools, this work offers a thorough exploration of quantum cryptography by B92 protocol’s principles.

Satellite-based quantum communications represent a critical advancement in the pursuit of secure, global-scale quantum networks. Leveraging the principles of quantum mechanics, these systems offer unparalleled security through Quantum Key Distribution and other quantum communication protocols. This review provides a comprehensive overview of the current state of satellite-based quantum communications, focusing on the evolution from terrestrial to space-based systems. We explore the distinct advantages and challenges of discrete-variable and continuous-variable quantum communication technologies in the context of satellite deployments. The paper also discusses key milestones, such as the successful implementation of quantum communication via the Micius satellite, and outlines the primary challenges, including atmospheric turbulence and the development of quantum repeaters, which must be addressed to achieve a global quantum internet. This review aims to consolidate recent advancements in the field, providing insight and perspectives on the future directions and potential innovations that will drive the continued evolution of satellite-based quantum communications.