Ghost imaging is a complex and incredibly useful set of techniques that scientists use to photograph light-sensitive objects at surprisingly high resolution. Using a combination of quantum and classical phenomena to extract visual information from just one of a pair of entangled photons, the method can capture images where energetic beams of light or radiation risk damaging the material of interest.

New research has demonstrated a way to improve ghosting without adding significant cost or complexity. Simply put, this means that these methods can capture more details from more objects. In quantum entanglement, unobservable pairs or groups of particles separate after some interaction. In this unobservable situation, its individual characteristics are a blur of probability yet to be determined by measurement. But whatever their fate, this final measurement will be correlated with measurements of particles they’ve encountered in the past.

In the ghost image, these unobservable particles are photons. One is sent to interact with the object before being caught by a simple detector. A second photon is sent the other way for careful study and detailed measurement. Although she actually saw nothing during her journey, the condition of this second photon can provide a surprising amount of detail about her partner’s experience.

“We send one of the mixed photons to an object that we want to look at in the dark, and by looking at the photon we have left, we can see the properties of the object in the dark,” says quantum physicist Berenijs. Sefton of the University of the Witwatersrand, Johannesburg, South Africa.

So far so smart. But what Sefton and his colleagues were able to do was improve this approach by changing the way photons interact with the environment in their detection path. These changes affect what is called the probability distribution or phase of each particle, providing a new layer of information that can be used to draw additional conclusions about the size, shape, and other properties of the object one of them encounters.

By squeezing a few more details from their phases, researchers can improve the camera’s resolution to display ghosts. What’s striking about the study is that this isn’t a radical change to how shadowing was previously done – rather it acknowledges that some of the previously hidden “side effects” of shadowing can be beneficial in the process.