An "Eternal Engine" has Been Developed by UK Scientists to Power the Atomic Clocks of the Future

Eternal Engine

For systems like global navigation, satellite mapping, determining the composition of exoplanets, and the next generations of communications, precision timing, measured using ultra-precise atomic clocks, is crucial. The current iterations of atomic clocks are massive things, weighing hundreds of kilograms, and must be kept in precise, challenging-to-maintain environments. Because of this, researchers are scrambling to create portable models that might displace current satellite navigation systems like GPS and Galileo and function in real-world environments. They refer to it as an ‘eternal engine’.

Now, research from the University of Sussex and Loughborough University has overcome a significant hurdle in the creation of these portable atomic clocks by figuring out how to dependably turn on and maintain the operation of their counting mechanism.

Future optical atomic clocks will need microcombs because they make it possible to count the oscillation of the clock’s “atomic pendulum,” which oscillates at a frequency of one billion times per second (a gigahertz frequency that can be measured by contemporary electronic systems).

Microcombs are the greatest contenders to miniaturize the next generation of ultra-precise timekeeping since they are based on electronic compatible optical microchips. They are state-of-the-art laser sources composed of comb-like, evenly spaced laser lines with extreme precision.

The finding of exoplanets or the development of ultra-sensitive medical devices based only on breath scans might both be facilitated by this unusual spectrum’s wide range of potential uses.

“None of this will ever be possible if the microcombs are so sensitive that they cannot maintain their state even if someone just enters in the lab” remarked Professor Alessia Pasquazi, whose team moved to Loughborough University last month after starting this ERC and EPSRC sponsored study at the University of Sussex.

Research conducted at the University of Sussex by Prof. Pasquazi and her colleagues has shown a method to enable the system to start by itself and remain in a stable state—basically, to be self-recovering—in a recent publication published in the journal Nature.

“We have basically an ‘eternal engine’ — like Snowpiercer if you watch it — which always comes back to the same state if something happens to disrupt it,” Professor Pasquazi said.

“A well-behaved microcomb uses a special type of wave, called a cavity-soliton, which is not simple to get. Like the engine of a petrol car, a microcomb prefers to stay in an ‘off-state’. When you start your car, you need a starter motor that makes the engine rotate properly.” Pasquazi continued. “At the moment, microcombs do not have a good ‘starter-motor’. It is like having your car with the battery constantly broken, and you need someone to push it downhill every time you need to use it, hoping that it will start. If you imagine that usually a cavity-soliton disappears in a microcomb laser when someone simply talks in the room, you see that we have a problem here.”

While leading the newly funded Emergent Photonic Research Centre at Loughborough University, Professor Marco Peccianti, who collaborated on the study at the University of Sussex, added: “In 2019 we had already demonstrated that we could use a different type of wave to get microcombs.”

“We called them laser cavity solitons because we embedded directly the microchip in a standard laser and we obtained a great boost in the efficiency.”

“We have shown now that our soliton can be naturally turned into the only state of the system, and we call this process ‘self-emergence’.”

EPSRC research fellow in quantum technologies at Loughborough, Dr. Juan Sebastian Totero Gongora, said that the system works like a simple thermodynamic system, which is governed by global variables such as pressure and atmospheric temperature.

“At atmospheric pressure, you are always sure to find water as ice at -5 degrees or as vapour above 100 degrees, whatever has happened to the water molecules before.”

Dr. Maxwell Rowley, who developed this device with Prof. Pasquazi while earning his PhD at the University of Sussex, is currently employed by CPI TMD Technologies, a branch of Communications & Power Industries (CPI), where work on commercializing the microcomb is ongoing, added that “Similarly, when we set the electrical current driving the laser to the appropriate value, here we are guaranteed that the microcomb will operate in our desired soliton state. It is a set-and-forget system — an ‘eternal engine’ that always recover the correct state.”

The paper, “Self-emergence of robust solitons in a micro-cavity,” was published in the last week, a culmination of the collaboration between associates from a number of universities, namely:

  • The University of Sussex
  • City University of Hong Kong
  • The Xi’an Institute of Optics and Precision Mechanics, in China
  • Swinburne University of Technology, in Australia.
  • The INRS-EMT, in Canada
  • The University of Strathclyde

One of the main objectives of the newly financed Emergent Photonics Laboratory Research Centre, which will concentrate on leading-edge optical technologies at Loughborough, is the pursuit of this technology.

The microcomb is a crucial part in building a portable, ultra-accurate time reference, which is essential for network synchronization (such as electrical networks) and the present and future generations of telecommunication (5 and 6G+). It will also lessen our reliance on the GPS.

With the help of CPI TMD technologies and under the leadership of Professor Matthias Keller at the University of Sussex, the self-emergent microcombs will be used directly in optical-fibre-based calcium ion references. They are also being developed as part of a larger collaboration on Quantum Technologies with co-author Professor Roberto Morandotti at the Canadian Institut national de la recherche scientifique (INRS).

According to Professor Paquazi, microcombs are expected to revolutionize telecommunications networks that utilize numerous colors to transfer and transmit as much information as possible. Currently, Paquazi states, networks use a different laser for every color, which is not as power efficient or as compact as using microcombes. Papuazi, in collaboration with Swinburne University and co-author Prof. David Moss, is pursuing next generation telecoms technologies.

With their collaboration with the astronomy department, Paquazi hopes that one day ‘optical rulers’ will aid in the exploration of our solar system, and the detection of exoplanets.

Materials provided by University of Sussex. Original written by Vicky Trendall Lane. Note: Content may be edited for style and length.

Original Story Citation: University of Sussex. “Scientists create an ‘eternal engine’ to keep the next generation of atomic clock ticking.” ScienceDaily. ScienceDaily, 12 August 2022.

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