Public summary PhD-thesis Roy Op het Veld

Nanowire networks as a platform for quantum computing

June 18, 2021

Quantum technologies are considered to be the tools for the next big leap forward in the evolution of human society. Specifically, quantum computing is expected to tackle problems that have so far been difficult or even impossible to solve. In the development of such a fast computer, materials are very important. TU/e researcher Roy Op het Veld therefore managed to grow semiconductor nanowires in a scalable network, which could act as a platform for quantum computing.

Quantum computers use the principles of quantum physics to perform computations and store data. As the classical computer has a bit as their smallest information unit which can take the value 1 or 0, a quantum computer calculates with qubits. These qubits work in clusters and can exist in more than one state - e.g. 1 and 0 at the same time, but can also take every value in between - resulting in transmitting numerous information simultaneously. Currently, there are different ideas and approaches for quantum computation. Although some claim to have achieved multi-qubit computations already, none of these techniques have been able to demonstrate a commercially viable machine.

One of these ideas is the use of topological quantum computations by using Majorana fermions. Topology, the description of a geometric object when it is being deformed, is predicted to be useful to stabilize or ‘preserve’ a quantum state. This makes it possible to scale to larger quantum systems. To make a topological quantum bit, in which a Majorana state could potentially carry the quantum information, physicist Roy Op het Veld worked on developing a scalable system of superconductor-semiconductor hybrid nanowire networks which can be used in the next generation of devices. As the wires should be as thin and clean as possible, resulting in high quality networks, Op het Veld created a new protocol.

In his method, In-plane Selective Area Networks (InSANe) of InSb nanowires on InP substrates, he deposits an amorphous mask on an InP substrate and creates predefined openings in this mask using lithography. To get closer to the full in-situ fabrication of a device, unleashing the full potential of the scalable in-plane platform, Op het Veld achieved selective metal-on-semiconductor deposition by using grown InP walls as shadowing objects. Furthermore, in-situ shadow deposition allows an ultraclean interface of metal and semiconductor, and eliminates the need for any metal etchant, enabling the possibility for the in-situ deposition of two different metals selectively on different parts of the InSb nanowire network.

Although the newly designed platform of Op in het Veld is still in early fundamental stages and has not produced a qubit yet, it has the potential in the near future to host Majorana fermions and could thereby make the first topological quantum computer a step closer to reality.


Title of PhD-thesis: InSANe InSb Nanowire Quantum Devices. Supervisors: prof. Erik P.A.M. Bakkers and Marcel A. Verheijen