Spin-based quantum memory coupled to superconducting qubits in a Hybrid Quantum Architecture

ended

HyQuArch aims to provide top-level scientific outputs and training in the field of solid-state quantum technologies. Its main goal is to set-up the technical foundations of a Hybrid Quantum Architecture that couples a random-access quantum memory, the spins of nitrogen-vacancy (NV) centres in a diamond crystal, to several superconducting flux qubits acting as quantum processors. Superconducting cavities will turn on and off the communication between these components and perform operation and read-out protocols. The outgoing phase will take place at the USTC in Shanghai, while the return phase will develop at INMA in Zaragoza. First, several strategies will be combined to: a) enhance the ensemble-qubit coupling and b) minimize the environmental noise suffered by NV spins. The former goal will be addressed by fabricating the superconducting circuits onto diamond substrates and by using superconducting lumped element resonators to confine and enhance the microwave magnetic fields that mediate the transfer of quantum information. Longer storage lifetimes, thus higher state transfer fidelities, will be achieved by lowering the NVs concentration. Next, the focus will be on designing and implementing complex microwave pulse sequences to operate the quantum components and to exchange quantum information between them. Attaining these targets will enable storing entangled quantum states of two flux qubits in the quantum memory, a milestone that has remained elusive up to now. The return phase will be centred on the standardization of the technologies developed in Shanghai. Via collaboration with private stakeholders, the use of FPGA integrated circuits will lead to the development of low latency libraries for operating qRAMs. These advances will also enrich other quantum technologies pursued at CSIC. In particular, the final prototype will be applied to introduce a qRAM unit and tuneable couplers to boost the computational power of a quantum processor based on spin qudits.