Combining multiple rare-earth ion species into a single quantum computer

Quantum computing (QC) is one of the great challenges of our time, with promises to transform many problems from intractable to doable, e.g. in the development of medication, materials and AI.

Although the current leading approaches, superconducting qubits and trapped ions, have shown progress with a few tens of qubits, there is currently no clear path to full scalability. This project aims at showing the viability of a contender to scalable QC, using rare-earth (RE) ions.

The applicant recently led the efforts of writing a roadmap to RE QC, which has clarified its strengths of high qubit density and excellent integration capabilities, while also identifying a path to scalability using combinations of different species for different roles within QC, such as qubits or readout.

I propose to demonstrate four critical tasks aimed at realizing the main ideas of this roadmap:Demonstrate state selective single ion detectionDemonstrate that different RE species can perform different tasksVerify high fidelity gate operationsRealize entanglement between qubit ionsTasks 1 and 2 define the core idea, while tasks 3 and 4 demonstrate that the principles are scalable to larger systems.

Each task is expected to take about 1-year.

This project is crucial to reap the benefits of preparations and lab build-up accomplished by the applicant during an EU-flagship project. A successful project will solidify the RE concept as one of the primary candidates for long-term scalable QC.