Superconductivity has been at the forefront of scientific research for decades, however, a lack of meaningful theory exists for rotational dynamics and spin currents in superconductor-ferromagnetic systems. Our research objective was to develop a theoretical model describing the precession of flux-pinned magnetized materials in addition to the subsequent generation of spin currents within the superconductor. Our mathematical analysis incorporated thermal, electromagnetic, and quantum phenomena, including the Bloch-3/2 relation, Barnett effect, and spin-enhanced electron-phonon coupling. We further developed a novel consideration of the London moment in the vortex state as well as a framework for spin currents in superconductors dependent on the applied magnetic field and rotation of the superconductor. Conclusive data was first provided by MATLAB simulations, allowing us to identify the steady-state solutions to our mathematical model as well as perform critical field calculations for various superconductors. We further introduced experimental test benches for a yttrium barium copper oxide (YBCO) superconductor, particularly focusing on verifying our model for the precession of ferromagnets as well as the detection and measurement of spin currents. A statistical analysis revealed p-values below .0005 displaying the statistical significance of our results.Ultimately, we look to apply these models to deep space exploration, improving the integration of superconductors into spacecraft. The steady-state rotation of a ferromagnet levitated above a superconductor (or vice versa) can be used to enhance existing London moment gyroscopes and superconducting quantum interference devices (SQUIDs) for application to inertial navigation systems such as control moment gyroscopes. Additional applications include electricity generation for application to magnetoplasmadynamic thrusters and utilizing Abrikosov vortex dynamics and spin currents in superconductors for spintronic data storage and logical computations.

Modern day spintronic devices require the use of strong ferromagnets and precise magnetic fields to generate and control spin-polarized current, restricting their efficiency and applications to low-temperature environments where external fields have little impact on the hamiltonian of the spin-state system. Our research objective was to investigate the use of chiral single-walled carbon nanotubes (SWCNTs) as an alternative method to create and manipulate spin polarized current in a routine environment using the chirality induced spin selectivity (CISS) effect. We hypothesized the application of SWCNTs to act as an effective helicity filter and spin polarizer for electrons to then apply their spin transfer torque to a magnetically permeable layer. To test this, we deposited two chiralities of carbon nanotubes onto soft ferromagnetic foil. Constant current was run through the apparatus while a magnetometer was used to measure changes in the surrounding magnetic field. Compared to the control group (mean difference of 1.109 microtesla, SD of 0.746), the metallic chiral group resulted in a much larger mean difference (3.706) with similar SD (0.727). Similarly, the semiconducting chiral group of nanotubes resulted in a larger mean difference (4.160), again with similar SD (0.655). The p-values from both two-sample t-tests were less than 0.0001, indicating statistically significant results. This study showed that carbon nanotubes can act as an effective spin polarizer for current, and the CISS effect in conjunction with giant magnetoresistance allows for a universal magnetic memory storage method. Applications of this research pertain to Magnetoresistive-RAM cells in addition to the development of Spin Field Effect Transistors (SFETs) using the Rashba effect.

A multiparty continuous-variable quantum key distribution (CVQKD) algorithm still remains to be shown, which is the goal of this paper. In contrast to pair-wise discrete quantum key distribution, multiparty CVQKD has the advantage of better detection and measurement with homodyne detectors and higher efficiency quantum networks. We provide a rigorous theoretical argument in addition to a discussion on the relevant experimental conditions for the proposed protocol. Said protocol involves utilizing the quadrature entanglement and phase correlations in noncollinear cascaded spontanous parametric down conversions (SPDC) to share secure keys between N parties involving the quadrature measurement of coherent photon modes. We then build on this to describe the symmetries of potential quantum networks based off the protocol, aiming to maximize the connectivity and security over a single quantum key distribution. We evaluate the protocol in a variety of situations, finding that the protocol does not degrade in security, only efficiency as the number of parties increases as a result of the SPDC conversion efficiencies in different materials.