A quantum leap in sensing the quietest signals in nature

The result is a compact and practical tool that can detect incredibly faint signals – from brainwaves and heartbeats to distant earthquakes or ripples in space. It could one day be used in hospitals, space research or early-warning systems – anywhere we need to hear what was once thought impossible to detect.

You know the feeling

The closer you lean in to hear a whisper, the easier it is to miss it. Scientists have long faced a similar paradox: in quantum physics, the more precisely you try to measure something, the more you disturb it. That strange rule has made it incredibly hard to hear the quietest signals in nature – such as the flutter of a brainwave, the beat of a distant heart or a ripple in space from a faraway black hole.

Now, researchers at the Niels Bohr Institute of the University of Copenhagen, Denmark have found a way to turn this problem into a solution. Instead of fighting quantum noise, they have built a system in which the noise cancels itself – like using two perfectly tuned microphones to erase background hum and leave only the real signal behind.

“We have built something completely new,” explains Eugene Polzik, a professor who led the study. “One part is light made of two colours that are quantum linked. The other is a cloud of atoms – including one that acts as if it has negative mass. That sounds strange, but imagine a swing that moves the opposite way when pushed. When we bring these parts together using quantum-linked light, the noise cancels itself, and the signal comes through more clearly than ever before.”

“This is the first time such a hybrid quantum sensor has been constructed and tested – culminating more than two decades of work,” adds Polzik.

Read more here >>