Microwave quantum memories using solid state spins

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Hybrid quantum systems offer the exciting potential to connect different types of quantum system together to exploit their respective strengths. Superconducting qubits are well suited for performing quantum logic gates but have coherence times typically in the tens of us, while electron spins of donors in silicon have coherence times to 3 seconds, and their states can be stored and retrieved using coupled nuclear spins, offering coherence times of up to 3 hours. We have shown with collaborators in CEA Saclay that spins in silicon can be coupled to high Q factor superconducting cavities to yield Purcell enhanced relaxation of electron spins i.e. electron spins return to the ground state by emitting a microwave photon into the cavity. This lays the foundation for coherent magnetic coupling of individual spins to microwave photons and for interfacing superconducting qubits and spin memories using a superconducting resonator as a quantum bus. Such quantum memories could make use of dopant spins in silicon, or rare earth defects in solids. We have also demonstrated a multimode quantum memory protocol where multiple microwave qubit states can be stored and retrieved independently in an ensemble. This aim of this project is to use highly coherent spins in solid state material to store microwave photon states, as a resource for quantum information technologies. Such a quantum memory would be able to store and retrieve many such states with high fidelity, over times approaching seconds, and interface with one or more superconducting qubits.The research methodology, including new knowledge or techniques in engineering and physical sciences that will be investigated. The project methodology includes superconducting resonator design, modelling and nano micro fabrication, along with the investigation of novel spin systems and material hosts. Electron spin resonance will be used to study the spin coherence and line width properties, while implantation and annealing processes will be optimised to improve spin performance. A dilution refrigerator will be used to achieve high spin polarisation and ensure optimal operation of the superconducting qubits.The project is strongly aligned with EPSRCs Quantum Technologies programme, as well as the Quantum Computing and Simulation Hub. The project will benefit from ongoing academic collaborations with the group of Patrice Bertet CEA Saclay and Philippe Goldner Chemie ParisTech.