AVS 71 Session AQS-SuA: AVS Quantum Science Workshop Oral Session (ALL-INVITED SESSION)

Research in quantum computing has provided numerous new physical insights and the potential to exponentially increase computational power for solving significant problems in science and technology. The primary obstacle to building a scalable quantum computer is errors caused by decoherence. Topological quantum computing addresses this challenge by utilizing topological materials that inherently limit errors.

In this talk, I will discuss the engineering of topological superconductors that support Majorana zero-energy modes at the interface between a conventional superconductor (Aluminum) and a semiconductor with spin-orbit interaction (Indium Arsenide). I will present recent findings from the Microsoft Quantum team that indicate the emergence of topological superconductivity in proximitized semiconductor nanowires. Additionally, I will cover recent measurements of fermion parity, which represent a step towards the fusion of Majorana zero modes. Finally, I will outline a proposal for scalable quantum computing that involves topological qubits composed of superconducting islands in a Coulomb blockade regime, hosting aggregates of four or more Majorana zero modes.

Progress in superconducting qubit performance over the past three decades has led researchers to focus on scalable quantum computing. To achieve scalability, the following are among the desiderata: system stability, easy input/output, high component yields, low energy use, and predictable component performance with tight distributions. These demands are even more challenging for quantum computing.

The NY CREATES team, along with our partners, has taken on the scalability challenge by seeking to implement superconducting qubits at 300 mm wafer scale, leveraging state of the art tools and processes to support the development of a Superconducting Quantum Process Design Kit (PDK). A PDK will enable democratization of qubit design and fabrication for start-ups, academia and national labs - but a PDK is only as good as the fidelity with which fabricated devices meet the designer's intent. Hence it is critical to develop fabrication processes that are controlled and repeatable, in tools that are equipped with in situ monitors for process control.

This talk will describe our efforts to develop tantalum (Ta)-based qubits at 300 mm scale. We use α-Ta as the wiring material, and atomic layer deposited tantalum nitride in the tunnel barrier of the Josephson junction. The advantages provided by state-of-the-art 300 mm tools to enable in situ process monitoring and control will be described using a few examples from various stages of the process flow. This talk will discuss the impact of two-level systems in material surfaces and interfaces. We have addressed them in many ways - by burying some in a crystalline silicon matrix to eliminate air exposure, and by replacing native oxides with surface treatments providing improved physical characteristics. Implementation of integrated air bridges and lumped element resonators that use high kinetic inductance elements and capacitors that use crystalline silicon as the dielectric will be discussed. The talk will conclude with a description of the circuit elements that are being developed for the PDK cell library, both as ‘fixed geometry’ cells, and as parameterized cells.