High volume Fabrication Technique for 3D Superconducting Multi-Qubit Systems

Computers based on quantum-mechanical phenomena, if realized, could disrupt many computationally intense fields of science, including high-energy physics Complex physical problems require powerful machines consisting of many qubits arrayed in a high-speed network. High quality factor superconducting RF resonators coupled to Josephson junctions are one of the most promising solutions. However, currently, qubits are produced separately which requires manual interconnections between cavity resonators, lead to other performance limiting behavior and are hard to scale to larger systems. In response to this problem, we will develop a fabrication technique that allows drawing of niobium sheet to create a large number of quarter-wave storage resonators (QWR) at once, quickly and easily. The drawn sheet will be designed to support the deposition of the microstrip circuits needed for coupling to the QWR qubits. This also eliminates welded connections between the cavities, which is critical for achieving high Q-factors. In Phase I, we will design the layout of the multi-qubit system for two QWR qubits with a shape optimized for niobium forming techniques (Figure 1). We will perform electromagnetic and engineering design of the system and will produce a module from the niobium sheet by means of drawing. We will measure the tolerances and surface finishing of the fabricated cavity and prepare the module for RF tests. In Phase II we will build a 2-8 qubit system and test it at mK temperatures to determine the circuit performance such as resonator Q-factor and stripline cross talk. The emerging discipline of quantum computing, although presently in its infancy, is rapidly growing and has an explosive commercial potential. Upon successful completion of the Phase II work, RadiaBeam would be in an excellent position to establish its presence as a supplier of components for this growing field by leveraging the SRF technology developed in this project.