  A central challenge in developing quantum computers and long-range quantum
networks lies in the distribution of entanglement across many individually
controllable qubits. Colour centres in diamond have emerged as leading
solid-state 'artificial atom' qubits, enabling on-demand remote entanglement,
coherent control of over 10 ancillae qubits with minute-long coherence times,
and memory-enhanced quantum communication. A critical next step is to integrate
large numbers of artificial atoms with photonic architectures to enable
large-scale quantum information processing systems. To date, these efforts have
been stymied by qubit inhomogeneities, low device yield, and complex device
requirements. Here, we introduce a process for the high-yield heterogeneous
integration of 'quantum micro-chiplets' (QMCs) -- diamond waveguide arrays
containing highly coherent colour centres -- with an aluminium nitride (AlN)
photonic integrated circuit (PIC). Our process enables the development of a
72-channel defect-free array of germanium-vacancy (GeV) and silicon-vacancy
(SiV) colour centres in a PIC. Photoluminescence spectroscopy reveals long-term
stable and narrow average optical linewidths of 54 MHz (146 MHz) for GeV (SiV)
emitters, close to the lifetime-limited linewidth of 32 MHz (93 MHz).
Additionally, inhomogeneities in the individual qubits can be compensated in
situ with integrated tuning of the optical frequencies over 100 GHz. The
ability to assemble large numbers of nearly indistinguishable artificial atoms
into phase-stable PICs provides an architecture toward multiplexed quantum
repeaters and general-purpose quantum computers.
