atomikellot

Atomikellot, or atomic clocks, are devices that keep time with extraordinary accuracy by using the stable frequency of atomic transitions as a reference. The most common standard is the cesium-133 atom, and the second is defined as exactly 9,192,631,770 periods of the radiation corresponding to the cesium-133 ground-state hyperfine transition. Other clock types use rubidium or optical transitions in atoms such as strontium or ytterbium, which can offer higher stability.

Principle and operation: An oscillator generates a signal that is repeatedly compared with the chosen atomic transition. Feedback locks the oscillator to the atomic resonance, producing a precise time base. Cooling and trapping techniques are often used to reduce motion-related perturbations and improve accuracy, especially in optical clocks.

Types: Cesium fountain and beam clocks remain standard references for many applications. Rubidium clocks are compact and widely used in field equipment. Optical clocks, based on transitions in atoms like strontium or ytterbium, use optical frequencies and offer much higher potential accuracy and stability. Chip-scale atomic clocks provide portable timing for mobile and embedded systems.

Standards and time scales: International Atomic Time (TAI) aggregates the output of atomic clocks worldwide, while Coordinated Universal Time (UTC) adds leap seconds to stay aligned with Earth’s rotation. Optical clocks drive ongoing research and discussion about potential future redefinitions of the second, though the cesium-based definition remains current.

Applications: Atomic clocks enable precise telecommunications timing, global navigation satellite systems, scientific research, and high-precision time stamping for data networks and financial systems. They underpin modern infrastructure and fundamental physics experiments.