Atomic scale control and mechanical spin driving of a magnetic atom – MechaSpin

Thanks to their long coherence time, individual localized spins in semiconductors are promising qubits for the implementation in the solid state of emerging quantum technologies including quantum computing and quantum enhanced sensing. However, achieving long-range interaction between remote solid state spin qubits and placing individual localized spins carried by dopants or defects at desired locations, essential elements of practical device fabrication, are still challenging goals today. Phonon assisted spin-spin coupling in a mechanical resonator has been recently suggested as a promising route to mediate coherent interaction between localized remote spins. Surface acoustic waves, phonon-like excitations bound to the surface of a solid, are also proposed as efficient quantum bus enabling long-range coupling of a wide range of qubits. Developing such hybrid spin-mechanical systems will require arrays of identical spin qubits with large intrinsic spin to strain interaction.

Some magnetic atoms, as Chromium (Cr), incorporated in semiconductors can be strongly sensitive to lattice deformation. The spin of such individual magnetic atom can be probed optically when it is inserted in a quantum dot. Individual magnetic atoms can also be manipulated and implanted with the tip of a Scanning Tunneling Microscopes (STM) to create artificial structures of few atoms on a surface.

In the MechaSpin project, we will demonstrate the potential of using the spin of an individual Cr atom in a semiconductor quantum dot as an optically addressable qubit for hybrid spin-mechanical systems. The large intrinsic spin to strain coupling of Cr will permit to exploit its interaction with the strain field of a SAW for a mechanical driving of the Cr spin. We will determine at the single atom level the efficiency of the dynamical spin to strain coupling and mechanically probe the coherence of this spin qubit. This ensemble of experiments will be the first demonstration of a full coherent mechanical control at the single spin level. STM manipulation of individual atoms and STM-tip assisted substitution techniques will be explored to create arrays of Cr spins on a semiconductor. Experimental results obtained for Cr substitution on III-V and II-VI compounds, materials where substitutional Cr have different electrostatic properties, will be compared with ab initio modelling. This will shed a new light on this promising but underexplored technique. STM spectroscopy combined with ab initio modelling will be used to analyze the effect of local environment on the electronic and magnetic properties of individual Cr atoms.