Signs of interactive form of quantum matter

Multi-particle interactions within an atomic clock.

False-color images showing variations in atom numbers (1 to 5 atoms, left to right) and density in different lattice cells of JILA’s strontium lattice atomic clock. JILA researchers observed shifts in the clock’s frequency that arise from the emergence of multi-particle interactions when three or more atoms occupy a single cell. Credit: Aki Goban, Ye group/JILA
False-color images showing variations in atom numbers (1 to 5 atoms, left to right) and density in different lattice cells of JILA’s strontium lattice atomic clock. JILA researchers observed shifts in the clock’s frequency that arise from the emergence of multi-particle interactions when three or more atoms occupy a single cell. Credit: Aki Goban, Ye group/JILA

For the first ever time, JILA scientists have confined groups of a couple of atoms and precisely estimated their multi-particle cooperations inside an atomic clock. Doing so, scientists could control interacting quantum matter, which is expected to boost the performance of atomic clocks, many other types of sensors, and quantum information systems.

The work suggests first-ever quantitative proof of precisely what happens when packing together a couple of fermions—atoms that can’t be in a similar quantum state and location in the meantime.

NIST and JILA Fellow Jun Ye said, “We are trying to understand the emergence of complexity when multiple particles—atoms here—interact with each other. Even though we may understand the rules perfectly on how two atoms interact, when multiple atoms get together there are always surprises. We want to understand the surprises quantitatively.”

During the study, scientists used their three-dimensioned strontium lattice clock, which offers precise atom control. They made varieties of somewhere in the range of one and five atoms for each lattice cell, and after that utilized a laser to set the clock “ticking,” or exchanging at a particular frequency between two energy levels in the atoms. JILA’s new imaging method was utilized to gauge the atoms’ quantum states.

Scientists observed unforeseen outcomes when three or more molecules were as one out of a cell. The outcomes were nonlinear, or unpredicted dependent on past experience, a sign of multi-particle interactions. The specialists joined their estimations with hypothetical expectations by NIST partners Ana Maria Rey and Paul Julienne to reason that multi-particle connections happened.

They found that the clock’s frequency shifted unexpectedly when there are almost 3 atoms in the lattice site. The shift is different from what one would expect from summing up various pairs of atoms.

Ye said, “Once you get three atoms per cell, the rules change. This is because the atoms’ nuclear spins and electronic configurations play together to determine the overall quantum state, and the atoms can all interact simultaneously instead of in a pair-wise fashion.”

“Multi-particle effects also appeared in crowded lattice cells in the form of an unusual, rapid decay process. Two atoms per triad formed a molecule and one atom remained loose, but all had enough energy to escape the trap. By contrast, a single atom is likely to remain in a cell for a much longer time.”

“What this means is, we can make sure there is only one atom per cell in our atomic clock. Understanding of these processes will allow us to figure out a better path for making improved clocks, as particles inevitably will interact if we pack enough of them nearby to improve signal strength.”

Scientists additionally found that packing at least three particles into a cell could result in extensive, exceedingly entangled states, which means the atoms’ quantum properties were connected steadily. This basic technique for entangling numerous atoms might be a valuable asset for quantum data processing.

This research was conducted in collaboration with the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder. The paper is published online in the journal Nature.