&Bullet; physics 14, p30
Quantum technologies such as quantum computers require sources for entangled photon pairs. To create these pairs of photons, researchers typically use silicon-based devices in which the silicon sits on an insulator. Galan Moody and his colleagues from the University of California, Santa Barbara, wondered if they could replace silicon with aluminum gallium arsenide (AlGaAs), a material that has recently proven useful for classic photonics applications. The team showed that devices made from AlGaAs can generate entangled photons at a rate 1,000 times faster than devices made from other materials  .
Chip-sized devices for generating entangled photon pairs typically couple laser light into a photonic waveguide or an optical cavity. Individual photons in the laser are then destroyed by interaction with the material of the cavity, a process that creates two new – entangled – photons. The efficiency of this process depends on the size of the cavity and the properties of the material used.
With the same design, Moody and his colleagues tinkered with the size of the cavity and switched the material from silicon to AlGaAs. They found that they were able to significantly increase the efficiency of the process without impairing other important properties of the entangled photon pairs produced, such as the entanglement loyalty.
The 1000x increase in brightness the team achieved should allow them to create the same number of entangled photon pairs as other devices, but using lower powered lasers. As a result, the modified devices could use less electricity overall. AlGaAs could also be used to make the other components for quantum computers, so they could possibly be contained on a single chip. The team says that such integration would simplify device fabrication and facilitate all-on-chip quantum photonics systems.
Katherine Wright is assistant editor of physics.
- TJ Steiner et al., “Generation of ultra-bright entangled photon pairs from an AlGaAs-on-isolator-micro-ring resonator”, PRX quantum2, 010337 (2021).