The smallest of split seconds

The Ultra-precise, Shock-resistant Optical Clocks (USOC) project is led by Dr Richard Hobson and Dr Charles Baynham at the Department of Physics at Imperial College, London, with Dr Ian Hill from the UK’s National Physical Laboratory. Richard explains: “the atomic clocks that we have at the moment need to be encased in a sarcophagus of heavy metal shielding: there’s no way of taking them on a plane, say.  What we are exploring through the USOC project are ways of creating a conveyor-belt of ultra-cold atoms. By feeding this continuous stream of atoms into an atomic clock we can continuously measure the accuracy of the laser that we use, rather than doing so sporadically. As well as being more accurate, that makes the clock more robust and potentially smaller: small enough to go on a satellite, on a truck, on a submarine.”

The project is nine months in: a prototype should be ready later this year. For co-investigator Dr Charles Baynham, the new clocks could have important applications. “First, having more robust atomic clocks would mean that our timing infrastructure in the UK was more resilient against global satellite navigation systems (GNSS) outages. Even if these clocks were disconnected from the world for a long time, they would still be extremely accurate.”

With an ultra-precise clock, which can measure fluctuations in the rate of time, we can pick up on the tiniest shifts in gravity: enough to show that an earthquake is coming or to detect the smallest movements in tectonic plates

There is a security angle to this work, which is part-funded by the Defence Science and Technology Laboratory. GPS (on which so much of the UK’s critical infrastructure depends) works by sending out very accurate time signals, but these are very easy to block. An atomic clock couldn’t be blocked or turned off. 

The new clocks could have other applications, because of their ability to detect changes in gravity.  “General Relativity says that time slows down near heavy things,” says Charles Baynham. “This means that with an ultra-precise clock, which can measure fluctuations in the rate of time, we can pick up on the tiniest shifts in gravity: enough to show that an earthquake is coming, for example, or to detect the smallest movements in tectonic plates.”

“The new clock could also be able to detect some forms of Dark Matter that even CERN can’t find. Our clocks involve looking very carefully at pieces of matter – strontium in this case – and so we can spot any changes to that matter, including perhaps the very subtle changes that Dark Matter may bring about.”