Optical activation and detection of charge transport between individual color centers in room-temperature diamond

TL;DR

This study demonstrates optical control and detection of charge transport between individual nitrogen-vacancy centers in diamond at room temperature, revealing large carrier capture cross-sections and potential for quantum information applications.

Contribution

It introduces a novel confocal microscopy and magnetic resonance protocol to observe charge transfer between single NV centers, enabling quantum control at the defect level.

Findings

Charge transport between NV centers can be optically induced and detected.

Carrier capture cross-sections are significantly larger than in ensemble measurements.

Free carriers can potentially mediate interactions between defects in quantum devices.

Abstract

Charge control of color centers in semiconductors promises opportunities for novel forms of sensing and quantum information processing. Here, we articulate confocal fluorescence microscopy and magnetic resonance protocols to induce and probe charge transport between discrete sets of engineered nitrogen-vacancy (NV) centers in diamond, down to the level of individual defects. In our experiments, a "source" NV undergoes optically-driven cycles of ionization and recombination to produce a stream of photo-generated carriers, one of which we subsequently capture via a "target" NV several micrometers away. We use a spin-to-charge conversion scheme to encode the spin state of the source color center into the charge state of the target, in the process allowing us to set an upper bound to carrier injection from other background defects. We attribute our observations to the action of unscreened Coulomb potentials producing giant carrier capture cross-sections, orders of magnitude greater than those typically attained in ensemble measurements. Besides their fundamental interest, these results open intriguing prospects in the use of free carriers as a quantum bus to mediate effective interactions between paramagnetic defects in a solid-state chip.