Ali Rida ISMAIL: Commensurable and Chaotic NCVO Study for Information Processing

Abstract:
The amount of data used in information technology is increasing dramatically. This comes with the proliferation of highly advanced electronic technologies. The thermal issues, rising as an effect of such large data processes, impose the usage of novel technologies and paradigms in place of CMOS circuits. Spintronic devices are one of many alternatives proposed so far in the literature. In this work, we consider a spintronic device called nano-contact vortex oscillator (NCVO), which has recently begun to gain attention due to its rich and variable dynamics. This oscillators is operated by an bias DC current and subjected in a magnetic field, that determines it output dynamics. The practical use of the NCVO requires the existence of an accurate model that imitates its output magnetization and the vortex’s trajectory rotating around the center in the upper layer of the device. These two variables are needed for the calculation of the equivalent resistance of the NCVO. For that, we build in this PhD work a model for the NCVO producing these two variables using a reservoir computing approach called conceptor-driven network. The network is trained on NCVO data gained by micromagnetic simulation. The built model successfully captures the NCVO dynamics in its different regimes (chaotic, periodic, and quasi- periodic) with an easy shift between regimes. The same network is used then for the detection of chaos in the input-times series. The proposed chaos-detection method has shown to be efficient and more robust compared to existing methods. Finally, the NCVO model is exploited for truly random number generation (TRNG) where a hardware design, fed by a chaotic signal generated by the model, is proposed. This design has shown the ability to compete existing RNG techniques in terms of speed, cost, and quality.

Keywords:
information technology, beyond-CMOS, spintronics, NCVO, reservoir computing, chaos detection, TRNG

Composition of the jury :
> Reporters:
- Aida TODRI-SANIAL,
- Ian O'CONNOR,
> Examiner:
- Virginie FRESSE
> Direction of thesis:
- Hassan RABAH, Director of thesis
- Slavisa JOVANOVIC, Co-director of thesis
- Sébastien PETIT-WATELOT, Co-director of thesis