Marie Curie Actions: Inspiring Researchers - Imdea

Tick, tock – every lightoscillation countsGiven the outstanding quality of the top-of-the-range clocksavailable today, the need for greater precision may not beimmediately obvious. But in telecommunications, better clockswould be very welcome indeed – the smaller the units intowhich they can split individual seconds, the greater the amountof information that can be transmitted. And for systems whichdepend on synchronicity, the fact that all clocks run fast or slowto some extent remains a problem. Positioning systems, forexample, triangulate the exact location of objects based on thetime taken to receive their signal. Unless the systems are perfectlysynchronised, they could miss the mark by several metres.The key to clockwork precisionMicrowave atomic clocks, the most accurate timekeepingdevices in existence, are setting the standard, but even theycan be improved. The quest for greater precision took a youngresearcher from Latvia to the Max Planck Institute of QuantumOptics (MPQ) in Garching, Germany. During the Hydrogen 1S-2Sproject, Dr Janis Alnis studied a tiny energy shift in hydrogenatoms that results in a change of the hydrogen spectra, andinvestigated how this shift can be measured more accuratelywith the help of laser spectroscopy.‘Now we measure hydrogen with 14 digits of precision,’ heexplains. However, the aim is to be even more accurate: ‘Atpresent, microwave clocks enable us to measure with 15 digitsof precision, but optical standards would allow us to measurefrequency with 17 digits of precision, and so to measure timemore precisely. Optical clocks tick much faster than microwaveclocks, and the same number of ticks can be counted in ashorter time interval.’A the moment, the caesium atomic clock – in which amicrowave counter records the oscillations of the outerelectron in caesium atoms vibrating more than 9 billion timesper second – is considered to be the most accurate. An opticalatomic clock would potentially be up to a thousand timesHydrogen 1S-2S measurement in progress37