Scalable Feedback Stabilization of Quantum Light Sources on a CMOS Chip
Silicon photonics is a leading platform for realizing the vast numbers of physical qubits needed for useful quantum information processing because it leverages mature complementary metal-oxide-semiconductor (CMOS) manufacturing to integrate on-chip thousands of optical devices for generating and manipulating quantum states of light. A challenge to the practical operation and scale-up of silicon quantum-photonic integrated circuits, however, is the need to control their extreme sensitivity to process and temperature variations, free-carrier and self-heating nonlinearities, and thermal crosstalk. To date these challenges have been partially addressed using bulky off-chip electronics, sacrificing many benefits of a chip-scale platform. Here, we demonstrate the first electronic-photonic quantum system-on-chip (EPQSoC) consisting of quantum-correlated photon-pair sources stabilized via on-chip feedback control circuits, all fabricated in a high-volume 45nm CMOS microelectronics foundry. We use non-invasive photocurrent sensing in a tunable microring cavity photon-pair source to actively lock it to a fixed pump laser while operating in the quantum regime, enabling large scale microring-based quantum systems. In this first demonstration of such a capability, we achieve a high CAR of 134 with an ultra-low g(2)(0) of 0.021 at 2.2 kHz off-chip detected pair rate and 3.3 MHz/mW2 on-chip pair generation efficiency, and over 100 kHz off-chip detected pair rate at higher pump powers (1.5 MHz on-chip). These sources maintain stable quantum properties in the presence of temperature variations, operating reliably in practical settings with many adjacent devices creating thermal disturbances on the same chip. Such dense electronic-photonic integration enables implementation and control of quantum-photonic systems at the scale required for useful quantum information processing with CMOS-fabricated chips.