Hybrid diamond chip enables single-shot readout of quantum spins

Researchers demonstrated a gallium-phosphide-on-diamond chip that couples light strongly enough to a diamond quantum bit to read its electron spin in a single measurement. The work, published in Optica Quantum, addresses a component needed to transfer quantum information into optical networks. The team fabricated more than 600 light-trapping cavities on diamond with a 99.5% yield. Devices produced distinct optical signatures for different spin states and had spin-relaxation times exceeding 0.4 milliseconds. Connecting and entangling multiple devices on the same chip remains a next step.