Dynamics of a superconducting qubit coupled to the quantized cavity field: a unitary transformation approach

We present a novel approach for studying the dynamics of a superconducting qubit in a cavity. We succeed in linearizing the Hamiltonian through the application of an appropriate unitary transformation followed by a rotating wave approximation (RWA). For certain values of the parameters involved, we show that it is possible to obtain a a Jaynes-Cummings type Hamiltonian. As an example, we show the existence of super-revivals for the qubit inversion

Quantum Key Distribution using Continuous-variable non-Gaussian States

In this work we present a quantum key distribution protocol using continuous-variable non-Gaussian states, homodyne detection and post-selection. The employed signal states are the Photon Added then Subtracted Coherent States (PASCS) in which one photon is added and subsequently one photon is subtracted. We analyze the performance of our protocol, compared to a coherent state based protocol, for two different attacks that could be carried out by the eavesdropper (Eve). We calculate the secret key rate transmission in a lossy line for a superior channel (beam-splitter) attack, and we show that we may increase the secret key generation rate by using the non-Gaussian PASCS rather than coherent states. We also consider the simultaneous quadrature measurement (intercept-resend) attack and we show that the efficiency of Eve's attack is substantially reduced if PASCS are used as signal states.Comment: We have included an analysis of the simultaneous quadrature measurement attack plus 2 figures; we have also clarified some point

Transfer of coherence from atoms to mixed field states in a two-photon lossless micromaser

We propose a two-photon micromaser-based scheme for the generation of a nonclassical state from a mixed state. We conclude that a faster, as well as a higher degree of field purity is achieved in comparison to one-photon processes. We investigate the statistical properties of the resulting field states, for initial thermal and (phase-diffused) coherent states. Quasiprobabilities are employed to characterize the state of the generated fields.Comment: 20 pages, 8 figures, to appear in Journal of Modern Optic

The Paradox of Tik Tok Anti-Pro-Anorexia Videos: How Social Media Can Promote Non-Suicidal Self-Injury and Anorexia

The literature shows that social pressure promotes non-suicidal self-injury (NSSI) eating disorders, along with self-injury, are also favored by underregulated social media. Tik tok is one of the most used social media platforms among adolescents. It has been shown that the time young children spend on this platform doubled during the lockdown. The theme of anorexia is very common on this platform. While most "pro-ana" (pro-anorexia) videos, where users exchanged advice on how to pathologically lose weight, have been censored by the application, other "anti-pro-ana" (anti-pro-anorexia) videos, officially aimed at raising awareness of the consequences of anorexia, have become increasingly popular. However, our case shows how even these safer videos paradoxically lead the users to emulate these "guilty" behaviors