Chinese researchers have taken a significant step towards constructing quantum chips by creating a quantum light source using a conventional semiconductor for the first time.
Quantum chips have the potential to solve complex problems exponentially faster than conventional electronic-based computing, but scientists have been struggling to fabricate essential components for an integrated circuit.
A team in China now reports that they have created one such component—a quantum light source—using the semiconductor gallium nitride (GaN), a material that has been used in blue LEDs for decades.
The quantum light source has "considerable potential" for building compact, powerful quantum chips, according to the team from the University of Electronic Science and Technology of China (UESTC), Tsinghua University, and the Shanghai Institute of Microsystem and Information Technology. It generates entangled pairs of photons, particles of light that can be used as carriers of information.
In comparison with existing quantum light sources based on materials such as silicon nitride and indium phosphide, GaN has a much broader wavelength range and can potentially be used to build other key elements of a quantum circuit.
"We demonstrate that gallium nitride is a promising quantum material platform for quantum photonics, where the generation of quantum light is crucial," the researchers wrote in their study published in Physical Review Letters last month. "The gallium nitride platform holds promising prospects for the development of quantum photonic chips in the near future."
"The work by the Chinese team is 'a step towards' making devices cheaper, more compact, and more robust than is possible today," said Thomas Walther, an expert in quantum photonics at the Technical University of Darmstadt in Germany.
Quantum Light Source Using Gallium Nitride
In their experiment, Zhou and his colleagues first created a thin film of GaN on a sapphire substrate. They then etched a ring into the film, 120 micrometers in diameter, allowing photons from a laser beam to travel around the ring.
When the researchers shone infrared laser light on the GaN film, some photons became trapped and formed "resonances" in pairs. Due to an effect called spontaneous four-wave mixing, some of the pairs of resonances generated new pairs of photons that were linked in a special way.
Zhou said the entanglement generated by the GaN ring is "comparable" to that measured in other quantum light sources.
The output wavelength range was also extended, from 25.6 nanometers with previous materials to 100 nanometers with the new device.
"By offering more wavelength resources, we could potentially serve more users who wish to access the quantum network via different wavelengths," Zhou told Science and Technology Daily.
Potential for Other Quantum Circuit Components
In addition to the quantum light source, GaN is also a promising material for building other elements of a quantum circuit, including pump lasers and photon detectors, according to the team.
"In comparison with the existing platforms, GaN holds considerable potential for the implementation of a monolithic on-chip quantum photonic integrated circuit," the researchers wrote.
Summary
Chinese researchers have created a quantum light source using gallium nitride, a significant step towards building quantum chips. The new source has a broader wavelength range and can potentially be used to build other key elements of a quantum circuit, making it a promising material for the development of compact, powerful quantum chips.