Quantum transistor

A quantum computing device, comprising:

• an optical resonator having a resonant wavelength band;
• a crystalline material comprising a crystal defect contained within the optical resonator, the crystal defect having a ground state and an excited state, which has an emission wavelength in the resonant wavelength band;
• a source electrode and a drain electrode disposed on opposing sides of the crystal defect and configured to apply a first electric field in the crystalline material along a longitudinal axis;
• a gate electrode disposed in proximity to the crystal defect and configured to apply to the crystalline material a second electric field transverse to the longitudinal axis;
• semiconductor donor and acceptor layers overlying the crystalline material between at least one of the electrodes and the crystal defect;
• and
• control circuitry, which is configured to apply a first voltage between the source and drain electrodes to control a charge state of the crystal defect and to apply a second voltage to the gate electrode to tune the emission wavelength,
• wherein application of the first electric field releases carriers from the semiconductor donor layer to the semiconductor acceptor layer in a vicinity of the crystal defect to create a two-dimensional PIN structure over the crystal defect, and switching a polarity of the first voltage switches the charge state of the crystal defect by shifting positive and negative carrier bands in the crystalline material via the PIN structure over the crystal defect.