At the edge of a university rooftop in eastern China, scientists used a trick from astronomy to read an eight-millimeter-tall letter on a board perched atop a distant building, almost a mile away.

No camera should have been able to read it from that distance. But this time, the laws of optics got a little help.

The physicists fired eight infrared laser beams at the distant sign. Two telescopes sat side by side, collecting the returning flickers of light. Inside the instruments, quantum-level ripples were quietly at work. The team, led by researchers at the University of Science and Technology of China, reconstructed the hidden letter with startling clarity.

Their method — a refined form of intensity interferometry — lets scientists image distant, non-glowing objects with a resolution 14 times sharper than what a single optical telescope could deliver. The letter, just a third of an inch wide, was revealed in sharp relief, even through the shimmering turbulence of the atmosphere.

A Quantum Trick of the Light

To understand how this works, forget how regular cameras see. Most lenses capture the shape and color of objects based on the angle and phase of incoming light. But those methods buckle when the air is unstable, the target is faint, or the object doesn’t emit light on its own.

Intensity interferometry flips the script. Instead of tracking where photons are going, it watches how their intensity flickers from moment to moment.

At the heart of the method lies a weird quantum behavior. Light particles, or photons, arriving at two places at once can create subtle, synchronized fluctuations. This effect allows researchers to extract fine details about the source—without ever capturing a conventional image.

The idea isn’t new. In 1956, astronomers first used this method to measure the size of stars. But until recently, it remained mostly a cosmic tool, reserved for bright objects in the night sky.

Now, physicists have turned it downward — onto Earth.

Reading the Unseeable

To test their system, the Chinese team pasted shiny metal targets onto a distant building. Each bore a reflective letter no wider than a pea. They split a 100-milliwatt infrared laser into eight separate beams, each traveling through a slightly different slice of the atmosphere. This clever tweak introduced randomness in phase — making the light appear “incoherent,” even though it came from the same source.

Counterintuitively, that randomness was the secret ingredient. Without it, the laser’s internal “shot noise” would overwhelm any useful signal.

Two small telescopes collected the scattered light. By adjusting their separation — from 7 to 87 centimeters — and rotating the target through 360 degrees, the team could compare the intensity fluctuations between detectors. Then came the math: calculating the correlations, modeling the waveforms, and slowly piecing together the invisible shapes.

The final images were startling. Letters emerged at 3-millimeter resolution — a level of detail that, at this distance, would require massive optics if attempted by conventional means.

Using just one telescope, the resolution would’ve been 42 millimeters. That’s roughly the width of a matchbox — far too blurry to read text this small nearly a mile away.

From Space Junk to Insect Wings

What could this mean for science?

According to Qiang Zhang, one of the lead researchers, potential uses range from astronomy to agriculture. “A potential application might be space debris detection — the laser light could be shone on nearby orbiting objects,” he said.

Others imagine a wider landscape. “The new work represents a significant technical advancement in imaging distant objects that do not emit their own light,” said Shaurya Aarav, an optics researcher at Sorbonne University in France.

He envisions laser-interferometry systems mounted on drones or towers, silently watching remote forests or fields. With enough resolution, scientists could monitor insect swarms, track invasive species, or detect early signs of crop disease — without ever setting foot on the ground.

The system is still in its early stages. The team hopes to refine their laser controls and layer in deep learning algorithms to better identify patterns and shapes. But even in its prototype form, the work shows what’s possible when physics ventures beyond the lens.

“The fact that they can image millimeter-sized objects at over-kilometer distances is genuinely impressive,” Ilya Starshynov, an optics expert at the University of Glasgow, told Physics Magazine. He praised the “clever” approach to delivering incoherent light to a remote object.

The findings were reported in the journal Physical Review Letters.