Scientists have figured out how to measure tiny light delays with extreme precision, even when they are many times larger than the pulse's natural 'blurriness'. The method is akin to identifying a note from individual sound waves rather than the overall noise. This paves the way for ultra-sensitive sensors and quantum technologies. It's intriguing to think what other mysteries of the micro-world it might help uncover.
Quantum interference helps measure minuscule light delays. When two identical photons hit a semi-transparent mirror at the same time, they always exit together — like two musicians playing a note in perfect unison. But if one is delayed by picoseconds, the synchrony vanishes, and old detectors stop noticing it.
Physicists added spectroscopy to the detectors: now each one records not just a photon’s arrival, but also its frequency. It’s like your ear distinguishing not only loudness but also pitch, letting you hear dissonance even with a large time gap. Using an array of such detectors, scientists achieved photometric precision down to 10 picoseconds, even when the delay between photons exceeded their coherence time.
🎯 The idea of quantum interference of photons was first described by [scientist:Roy Glauber]Roy Glauber[/scientist], and experiments with entangled photons by [scientist:Anton Zeilinger]Anton Zeilinger[/scientist] laid the groundwork for ultra-precise measurements.