(Infoq) MIT researchers recently described a process to manufacture “artificial atoms” that can be integrated to create larger-scale quantum chips. As a proof of this, they built a 128-qubit chip, the largest yet.
The qubits in the new chip are artificial atoms made from defects in diamond, which can be prodded with visible light and microwaves to emit photons that carry quantum information.
Unfortunately, this approach, which is not new, does not lend itself to build system that can scale to thousands or millions of qubits, say the researchers. Hence, instead of attempting to build a larger chip in diamond, they preferred a modular approach using semiconductor fabrication techniques to integrate small chiplets of diamond into a larger hybrid and modular chip. This process uses a photonic integrated circuit, which is analogous to a traditional integrated circuit but carries information through photons instead of electrons.
Using this approach the researchers could connect 128 qubits on one aluminium nitride platform. Thanks to photoluminescence, they showed the qubits were stable and long-lived, and could furthermore be tuned to be spectrally indistinguishable.
The significance of this achievement is easy to understand if you think that, as the paper authors explain, a key challenge on the road to quantum computers is finding a way to control entanglement across large numbers of qubits.