Researchers produce photons that are almost perfectly indistinguishable

[Seb83]

Researchers from Paderborn University, the University of Basel and Ruhr University Bochum have found a way to make much higher quality photons for quantum technology. The work, led by Timon Baltisberger in Basel along with professors Stefan Schumacher, Richard Warburton and Klaus Jons, is published in Physical Review Letters, with more findings in Physical Review Applied. The headline result is a jump in photon indistinguishability from 60 percent to 90 percent. That might sound like a small technical detail, but it matters a great deal

Many quantum communication and photonic computing schemes rely on photons being identical. If two photons are even slightly different in timing, colour or polarisation, they will not interfere properly, and operations that depend on that interference start to fail. The more identical they are, the lower the error rate. So moving from 60 to 90 percent is a significant step. Photonic networks are especially sensitive to this

The team used a process called biexciton decay inside semiconductor quantum dots. A quantum dot that has been excited twice releases a pair of photons as it relaxes. By placing the dot inside a specially designed optical cavity, they sped up and controlled that emission. Schumacher said that integrating it into the cavity let them specifically accelerate and control the light emission process

There is still a limit, and it comes from vibrations in the crystal lattice, known as phonons. These currently stop the purity going higher, although the researchers believe that mechanism can be minimised in future designs. Quantum dots are attractive because they could, in principle, be mass produced on chips, which fits with the Quandela production line story we covered earlier this week

Photonic quantum tech gets less attention than superconducting or neutral atom machines, but it is crucial for quantum networks. Any quantum internet will need reliable sources of identical photons. Does anyone here work with photonics? How far off is 99 percent indistinguishability?

New Method Generates Photons That Are Virtually Indistinguishablethequantuminsider.com