Study of materials photoelectric properties and development of photoelectrically readout qubits

The development of photoelectrically readout solid-state qubits is one of the main activities of Imo-imomec QST division. Based on the group expertise in the field of defects photophysics, a method enabling the photoelectric detection of NV centres magnetic resonances (PDMR) was first demonstrated at Imo-imomec in 2015. It was since then further developed and optimized, enabling the photoelectric readout of coherently driven single electron and single nuclear spins. Based on the direct detection of free charge carriers resulting from color centres photoionization, this method does not require any complex collection optics and allows integration of the measurement circuitry directly on the diamond, thus bringing the quantum platform to an electronic chip. It also enables the spatially-resolved detection of single spins, with improved spatial resolution compared to optical detection.

From a fundamental point of view, the research currently performed on PDMR aims at better understanding the physical processes involved in spins photoelectric readout. This work includes the experimental study of color centres photophysics and ionization mechanisms using various sensitive spectroscopy techniques, the characterization of the diamond material electronic properties and the mathematical modelling of PDMR. The objective is, on the one hand, to further improve the photoelectric readout of NV centres spins in diamond and, on the other hand, to extend the PDMR method to different spin defects in diamond (e.g. group IV-Vacancy defects or Ni-associated defects) and to color centres in other wide-bandgap materials, especially silicon carbide.

From a technical point of view, current challenges include the fast detection of ultra-low photocurrents (to make the photoelectric readout compatible with pulsed protocols used for spin manipulations), the independent readout of adjacent micrometric sets of electrodes and the minimization of the technical noise (due in particular to cross-talks between the microwave field used for spin manipulations and the photocurrent detection path). Our work aims thus at improving all components of the diamond chip, including  electrodes, interconnectivity of the wire circuits on the diamond chip with the external control and readout electronics, and current amplifiers and detectors.