# Use a Quantum gas Clock to set Your Alarm Clock--it's the Most Precise Ever

World clock at Alexanderplatz in Berlin | Elena Fahro | Shutterstock.com

### Researchers have built the most accurate atomic clock ever made, which keeps time using a quantum gas.

It only takes a second to say “hi”. Lots of things happen each second.

Every second, 761 tons of CO2 are released into the planet’s atmosphere.

A photon travels 186,282 miles per second.

Just a second, friend!

What is a second? How long does it actually take?

This may sound trivial, but it has occupied physicists (and now Pharrell) for centuries.

As proposed by German mathematician Carl Friedrich Gauss (1777 – 1855), the second was one of 86,400 parts of a mean solar day.

Up to the 1950s, that was the definition of a second until scientists came to know that there are irregularities in Earth’s movement, and thus it greatly compromises timekeeping accuracy.

## The “Atomic Second” for More Accurate Time Measurement

In 1967, at the 13th CGPM (General Conference of Weights and Measures), the second was defined as “ the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom”, or the time a caesium-133 atom takes to transition between two energy states.

There’s an energy spectrum in which an atom can exist, that is, the energy of an atom can take only two states (referred to as hyperfine levels).

Atomic clocks are based on this fundamental principle of quantum physics

Since the energy differences between the states of an atom have perfectly defined values, the same applies to the frequency of the electromagnetic waves which can change their state.

A quantum-gas clock is off by 1 second every 90 billion years.Click To Tweet

An atomic clock uses the frequency of electromagnetic waves and counts its periods.

In the same way that a pendulum clock counts the swinging of the weight, or quartz clocks count the periods of the vibrations of its quartz oscillator, atomic clocks count the periods of the electromagnetic wave that caused the change of state of atoms.

The concept of “atomic clocks” was demonstrated as early as 1949, when the U.S. National Bureau of Standards (now NIST) built the first atomic timekeeping device, based on an ammonia molecule, but it was less accurate than its quartz counterparts of the day.

Measuring time with extraordinary accuracy to less than one second over millions of years, atomic clocks help synchronize satellites of the GPS system, telecommunication, and network data.

## Ultra-Precise Quantum-gas Atomic Timepiece

Most atomic clocks use the atoms of the cesium-133 isotope. However, the accuracy of cesium-based clocks is limited by the cesium electrons speed, as they can only oscillate 9,192,631,770 times per second between two energy levels.

In comparison, the electrons of strontium atoms can make the shift nearly one million billion times per second.

Three years ago, the most precise atomic clock would be off by one second in over 15 billions of years, which is about the age of the universe.

Now, researchers at JILA, the Joint Institute for Laboratory Astrophysics at the University of Colorado-Boulder, led by Jun Ye, built a quantum gas clock that only loses one second over about 90 billion years

As described in Science’s latest issue, the clock was created by trapping 87Sr (strontium) atoms into 3D lattices, or a cube made of laser beams, to constrain interaction between atoms and enhance measurement precision, unlike other atomic clocks that use 1D optical lattices.

“This new strontium clock using a quantum gas is an early and astounding success in the practical application of the ‘new quantum revolution,’ sometimes called ‘quantum 2.0’,” said NIST’s Thomas O’Brian, “This approach holds enormous promise for NIST and JILA to harness quantum correlations for a broad range of measurements and new  technologies, far beyond timing.”

### How important is accurate timing to you?

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#### Zayan Guedim

Trilingual poet, investigative journalist, and novelist. Zed loves tackling the big existential questions and all-things quantum.