Current Affairs

Entangled Atomic Clocks

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    Science & Technology
  • Published
    20th Sep, 2022


For the first time, scientists at the University of Oxford have been able to demonstrate a network of two entangled optical atomic clocks.

What are Atomic Clocks?

  • An atomic clock is a clock that uses the resonance frequencies of atoms as its resonator.
  • Cesium is incredibly accurate at timekeeping and is used in atomic clocks.


  • Entanglement is a quantum phenomenon in which two or more particles become linked together so that they can no longer be described independently, even at vast distances.
  • This is the key to reaching the fundamental limit of precision that’s determined by quantum theory.
  • Previous experiments have demonstrated that entanglement between two atomic clocks in the same system can be used to improve the quality of measurements.
  • This is the first-time researchers have been able to achieve this between clocks in two separate remotely entangled systems.

Why do we use clocks to navigate in space?

  • To determine a spacecraft’s distance from Earth, navigators send a signal to the spacecraft, which then returns it to Earth.
  • The time the signal requires to make that two-way journey reveals the spacecraft’s distance from Earth, because the signal travels at a known speed (the speed of light).
  • While it may sound complicated, most of us use this concept every day. The grocery store might be a 30-minute walk from your house.
  • If you know you can walk about a mile in 20 minutes, then you can calculate the distance to the store.
  • By sending multiple signals and taking many measurements over time, navigators can calculate a spacecraft’s trajectory: where it is and where it’s headed.

Need atomic clocks

  • To know the spacecraft’s position within a meter, navigators’ need clocks with precision time resolution — clocks that can measure billionths of a second.
  • Navigators also need clocks that are extremely stable.
  • Stability refers to how consistently a clock measures a unit of time; its measurement of the length of a second, for example, needs to be the same (to better than a billionth of a second) over days and weeks.

What is an oscillator in a clock?

  • Most modern clocks, from wristwatches to those used on satellites, keep time using a quartz crystal oscillator.
  • These devices take advantage of the fact that quartz crystals vibrate at a precise frequency when voltage is applied to them.
  • The vibrations of the crystal act like the pendulum of a grandfather clock, ticking off how much time has passed.

Verifying, please be patient.