Superconducting Quarter-Wave Resonator for Quantum Information Systems

Computers based on quantum-mechanical phenomena, if realized, could disrupt many computationally intense fields of science, including high-energy physics. One of the greatest challenges in building a quantum computer is improving the coherence of quantum states. High quality factor superconducting RF (SRF) resonators coupled to Josephson junctions are one of the most promising solutions. However, their designs are currently optimized for particle acceleration rather than hosting qubits. In response to this problem, we propose to develop an SRF cavity for quantum computers based on a quarter-wave resonator (QWR) with optimized shape, operating in the 6-10 GHz frequency region. A QWR is an attractive choice for the simplicity of its integration with the Josephson junction, which can be placed near the central conductor to allow higher coupling strength, and the feasibility of scaling it to multi-qubit system. In Phase I, we will optimize the shape of the proposed cavity and perform engineering and fabrication studies for the niobium prototype. In Phase II we will machine a cell out of niobium and perform cryogenic tests at Fermilab to demonstrate the required Quality-factors. We will investigate an aluminum resonator, for which we will have to develop cleaning, etching, and polishing techniques.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.