Most of us find it difficult to grasp the quantum world. According to Heisenberg’s uncertainty principle, it’s like observing a dance without being able to see simultaneously exactly where someone is dancing and how fast they’re moving—you always must choose to focus on one.

And yet, this quantum dance is far from chaotic; the dancers follow a strict choreography. In molecules, this strange behavior has another consequence: Even if a molecule should be completely frozen at absolute zero, it never truly comes to rest. The atoms it is made of perform a constant, never-ending quiet dance driven by so-called zero-point energy.

A new experimental design eliminates the top source of clock uncertainty.

Optical lattice clocks (OLCs) are among the world’s best atomic clocks. Their largest source of uncertainty results from the ubiquitous blackbody radiation (BBR). Now Youssef Hassan of the National Institute of Standards and Technology in Colorado and his colleagues have demonstrated a cryogenic OLC with a radiation shield that virtually eliminates BBR-associated uncertainty [1]. The researchers expect this OLC design to allow major improvements in clock accuracy.

In an OLC, hundreds to tens of thousands of atoms are lined up in a 1D lattice formed by a laser beam. A second (clock) beam, whose frequency can be tuned, then excites the atoms to a specific quantum state. The clock-beam frequency that maximizes the number of atoms making the transition defines the “ticking rate” of the OLC. BBR perturbs the atoms’ quantum states and decreases the OLC’s accuracy.