Thesis title: Frontiers in Magnetism

The end of Moore's Law is frequently predicted: the harbingers have been with us since 2004, when the progressive annual increase in computer clock speeds was frozen at around 4GHz to prevent the integrated circuits from overheating.

A potential solution to this impasse is the introduction of new computing hardware whose operation is predicated on manipulating quasiparticles that may be used to store, transfer and process information with minimal energy cost. The quasiparticle with the most versatility and promise is the magnon. It's already proved its capabilities in a range of analogue and digital computing devices. Still, no hard and fast overall paradigm has yet been set for magnonic computing. Therein lies the attraction and motivation for our proposed research.

A selection of eventual magnon computing architectures are possible. The most straightforward outcome is that it will transform the computing paradigms that we currently use and that are based on Abelian operation and Boolean algebra. In the unlikely event that magnonic computing potential goes this far and no further, it will still be a transformative step in computing technology which will enable Boolean computing to happen faster, use similar or smaller amounts of real estate and dissipate three orders of magnitude less heat for the same computing power.

A much more ambitious question - the motivation of this thesis - is if the potential performance of magnonic computing could go beyond what silicon offers. To address this we are borrowing from approaches taken in Quantum Computing, aiming to develop a thorough algebraic understanding of the behaviour of magnonic devices and exploit this understanding to have a rigorous approach to magnonic systems architecture. Our strategy is to examine and formalise mathematically the algebraic tools available to us in three existing or projected areas of magnonics - wave computing devices, quantum-style logic gates and magnonic analogue devices - and to use this approach to develop higher levels of novel computer architectures that these basic algebraic tools are capable of supporting.

Key questions we aim to address are:

1.What is the available fanout of this technology: that is the ability to couple outputs of one logic device into the inputs of more than one sequential device? This is a pivotal consideration in deciding the limits of what this technology is ultimately capable of.
2.How in practice can we exploit the ability of magnon devices to apply different operations simultaneously to multiple datastreams running in parallel on different frequency channels?
3. Can we run those datastreams sequentially through the same piece of hardware and perform different logical operations to the data on each passage. Specifically, can we take an output of a piece of hardware and inject it as an input to the same piece of hardware, but on a different channel?
4.How can we arrange the physical signposting of such datastreams such that they get coupled to the correct processing channels without crosstalk? In this capacity, can we use the non-degenerate four wave mixing building block that we made and tested in our recent work on magnon phase conjugation and that has two useful characteristics: the output is frequency shifted relative to the input and it tracks back along exactly the same physical path?
5. How can we interface such magnonic devices with one another and with conventional electronics in a way that is both energy efficient and is capable of transferring data reliably from wave to pulse format?
6. Are we capable of making magnonic devices with similar algebraic properties to quantum computing style logic elements and can these be used to improve or streamline existing magnonic logic configurations?
7. What role is there for analogue magnonic processors and can they be integrated successfully with digital wave technology?
Collaborators: Ecotricity
Alignment with EPSRC aims: Novel Computing Parad