Zurich researchers create quantum light

Some materials spontaneously emit light if they are excited by an external source, for instance a laser, explained the Swiss Federal Laboratories for Materials Science and Technology (Empa) in a statement. A much stronger emission of light can occur when the emitters synchronize and act together rather than independently when excited – but this can only occur when the emitters fulfill stringent requirements, such as having the same emission energy.  

Such strong emission has not been possible until now using technologically relevant materials, with researchers from Empa, the Federal Institute of Technology in Zurich (ETH) and IBM Research Zurich at last making a breakthrough in the field. In their study published in the journal “Nature”, they used perovskite quantum dots to create superfluorescence.

Using the most recent generation of quantum dots made of lead halide perovskites, which they arranged into a three-dimensional superlattice, they showed the path to superfluoresence, according to the statement. The superlattice is a solid synthetic body comprising periodically recurring thin layers, which “provides the basis for sources of entangled multi-photon states, a missing key resource for quantum sensing, quantum imaging and photonic quantum computing”. To achieve coherent coupling, the quantum dots must all have the same size, shape and composition – a synthesis the researchers have optimized over the last few years.

The researchers gave final proof of superfluorescence and quantum light with optical experiments performed at temperatures of around minus 267 degrees Celsius. “This was our ‘Eureka!‘ moment. The moment we realized that this was a novel quantum light source,” commented Gabriele Rainó from the ETH and Empa.