In the near future, quantum computers are set to revolutionize the way we compute, with new ways to explore databases, AI systems, simulations and more. But to realize this new application of quantum technology, photonic integrated circuits that can precisely control quantum states – called qubits – are needed. Scientists from Helmholtz-Zentrum Dresden-Rossendorf (HZDR), TU Dresden and Leibniz-Institut für Kristallzüchtung (IKZ) have made progress in this effort: for the first time, they have demonstrated controllability of emitters with single photons (Let there be light (Control)) at the nanoscale. silicon, as they report in Nature Communications (DOI: 10.1038/s41467-022-35051-5).
Photonic integrated circuits, or in short, PIC, use particles of light, commonly known as photons, as opposed to electrons from electronic integrated circuits. The main difference between the two: the photonic integrated circuit provides a function for the information signal placed in the optical wavelengths usually in the near-infrared range. “In fact, these PICs have many integrated photonic components capable of generating, routing, processing and detecting light on a single chip,” Dr. Georgy Astakhov, head of quantum technology at the Institute of Ion Beam Physics at the HZDR Materials Research Center says., adding: “This model is ready to play an important role in future technologies, such as quantum computing, and PIC will lead the way.
Initially, quantum photonics experiments were known for the extensive use of “extensive optics” spread over the optical table and occupying the entire laboratory. Today, photonic chips are changing this landscape dramatically. Small size, stability and suitability for mass production can make it the workhorse of modern quantum photonics.
From randomness to a controlled state
Monolithic integration of single photonic sources in a controlled manner will provide an efficient way to implement millions of photonic qubits in PICs. In order to do the math, these photons must be undetectable. With this, the production of photonic quantum processors in industrial scale will be possible.
However, the manufacturing process currently in place limits the compatibility of this promising concept with today’s semiconductor technology.
In the first attempt reported about two years ago, researchers have already been able to create a single photon on a silicon wafer, but only in an unpredictable way. Since then, they have come a long way. “Now, we show how to focus ion beams from a liquid metal alloy ion source to put one-photon emitters in the desired position on the wafer while gaining high performance and high spectral quality.”, Dr. Nico Klingner, physicist explains.
In addition, HZDR scientists subjected a single-photon camera to a rigorous program of material testing: after several cycles of cooling and heating, they did not see any damage to their optics. These results meet the requirements for further production.
To translate this result into a widespread technology and enable the atomic-scale engineering of photon emitters that are compatible with basic manufacturing, the team created a wide-scale installation in a commercial installation through the mask defined by lithography. Ciarán Fowley, head of the Clean room team and head of research and development at Rossendorf says: “This project allowed us to use the space in the clean room and the lithography machine to process the modern silicon.
Using these two methods, the team was able to create multiple single-photon photodiode arrays at pre-defined locations with spatial precision of around 50 nm. They transmit in the O-band of important telecommunications and show stable operation for days under continuous wave excitation.
Scientists are convinced that achieving the production of single photons in silicon makes them a promising candidate for quantum photonic technology, with manufacturing methods suitable for large-scale integration. These single-photon diodes are now technologically ready for fabrication in the semiconductor industry and for integration into existing telecommunications equipment.
