We perform resonant spectroscopy of erbium implanted into nanophotonic silicon waveguides, finding 1 GHz inhomogeneous broadening and homogeneous linewidths below 0.1 GHz. Our study thus introduces a promising materials platform for on-chip quantum information processing.
The realization of a scalable architecture for quantum information processing is a major challenge for quantum science.A promising approach is based on emitters in nanostructures that are coupled by light.Here, we show that erbium dopants can be reproducibly integrated at well-defined lattice sites by implantation into pure silicon.We thus achieve a narrow inhomogeneous broadening, less than 1 GHz, strong optical transitions, and an outstanding optical coherence even at temperatures of 8 K, with an upper bound to the homogeneous linewidth of around 10 kHz.Our study thus introduces a promising materials platform for the implementation of on-chip quantum memories, microwave-to-optical conversion, and distributed quantum information processing.
Quantum memories integrated into nanophotonic silicon devices are a promising platform for large quantum networks and scalable photonic quantum computers. In this context, erbium dopants are particularly attractive, as they combine optical transitions in the telecommunications frequency band with the potential for second-long coherence time. Here, we show that these emitters can be reliably integrated into commercially fabricated low-loss waveguides. We investigate several integration procedures and obtain ensembles of many emitters with an inhomogeneous broadening of <2 GHz and a homogeneous linewidth of <30 kHz. We further observe the splitting of the electronic spin states in a magnetic field up to 9 T that freezes paramagnetic impurities. Our findings are an important step toward long-lived quantum memories that can be fabricated on a wafer-scale using CMOS technology.
Integrated photonic circuits offer great promise for quantum technologies. However, due to the rapid propagation of light, many envisioned applications require efficient on-chip quantum memories with a programmable delay, compact footprint, and high fidelity. Implementing this based on standard semiconductor processing technology is an outstanding challenge. Here, we realize such memories using erbium-doped silicon waveguides, fabricated as part of a multi-wafer project by a nanophotonic foundry. We demonstrate light storage with a 44.2(9)MHz bandwidth and a programmable delay exceeding 1μs in a device with a footprint of only 1.5×10−2mm2, outperforming on-chip delay lines by many orders of magnitude. The phase of the read-out light field is preserved with a visibility of 91.3(30)%. The efficiency of 1.89(28)×10−8 can be improved in future devices through resonator enhancement and higher dopant concentrations. With this, the demonstrated approach will pave the way towards applications in photonic quantum computing based on scalable silicon processing technology.