Light from tiny perovskite crystals is like a choir performance, where voices sound sometimes solo, sometimes in a tight duet. Previously, such a duet could only be heard under extreme cooling, nearly to the chill of outer space. Now the choir sings at room temperature.
Scientists assembled ordered islands of quantum dots CsPbBr3, sized 100–500 nanometers — hundreds of times thinner than a human hair. These islands blink as one, but emit light in pairs. The degree of pairing reaches 2.75—meaning photons are born together noticeably more often than by chance.
The secret is that within an island, excitation energy, like a relay baton, passes from dot to dot and finds a single trap. There, two photons are born in a cascade, one after another. Such a cascade is the key to creating entangled photons needed for quantum communication and computing.
Now perovskite islands could become the basis for inexpensive, scalable quantum light sources. The choir has sung in duet, and soon we might hear entire quantum symphonies.
Perovskite quantum dots are so tiny that thousands would fit across a human hair, and their light can be seen under an ordinary microscope.