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.