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JILA researchers have, for the first time, isolated groups of a few atoms and accurately measured their multiparticle interactions within an atomic clock. This breakthrough will help scientists control interacting quantum matter, which should improve the performance of atomic clocks, many other types of sensors, and quantum information systems.
The research is described in a Nature The document was posted online early on October 31st. JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.
NIST scientists have for years predicted the physics of "many bodies" and its benefits, but JILA's new work provides the first quantitative proof of exactly what happens when we gather a few fermions – atoms that can not be found in the same quantum state. the same time.
"We are trying to understand the emergence of complexity when many particles – the atoms here – interact with each other," said NIST and JILA member Jun Ye. "Even though we understand perfectly the rules governing the interaction of two atoms, when several atoms meet, there are always surprises.We want to understand the surprises in a quantitative way."
The best current tools for measuring quantities such as time and frequency are based on the control of individual quantum particles. This is the case even when sets of thousands of atoms are used in an atomic clock. These measurements are close to the so-called standard quantum limit – a "wall" that prevents any further enhancement using independent particles.
Exploiting the interactions between many particles could knock down this wall, or even break it, because a modified quantum state could suppress atomic collisions and protect quantum states from interference or noise. Furthermore, in such systems, the atoms could be arranged to suppress quantum noise so that the sensors improve as the number of atoms increases, which promises to significant progress in terms of accuracy and data processing capacity.
In the new research, the JILA team used its three-dimensional strontium latch clock], which offers precise control of atoms. They created matrices comprising between one and five atoms per lattice cell, then used a laser to set the clock tick or to switch to a specific frequency between two energy levels in the lattices. atoms. JILA's new imaging technique has been used to measure the quantum states of atoms.
The researchers observed unexpected results when three or more atoms were together in a cell. The results were non-linear, or not predicted based on past experience, a feature of multi-particle interactions. The researchers combined their measurements with the theoretical predictions of NIST colleagues Ana Maria Rey and Paul Julienne to conclude the presence of multiparticle interactions.
Specifically, the clock frequency unexpectedly changed when three or more atoms were in a network site. The lag is different from what one would expect by summing different pairs of atoms. For example, five atoms per cell caused a shift of 20% from what could normally be expected.
"Once you get three atoms per cell, the rules change," said Ye. Indeed, nuclear spins and electronic configurations of atoms play together to determine the overall quantum state, and atoms can all interact simultaneously, not in pairs, he said.
Multiparticle effects have also appeared in congested network cells in the form of an unusual process of rapid decay. Two atoms per triad formed one molecule and one atom remained loose, but all had enough energy to escape the trap. On the other hand, a single atom is likely to stay in a cell much longer, Ye said.
"It means we can make sure that there is only one atom per cell in our atomic clock," Ye said. "Understanding these processes will help us find a better way to improve clocks, because particles will inevitably interact if we pack enough around to improve signal strength."
The JILA team also discovered that packing three or more atoms in a cell could result in long-lasting, highly entangled states, meaning that the quantum properties of atoms were stably bound. This simple method of interlocking several atoms can be a useful resource for the processing of quantum information.
This research is supported by NIST, the Defense Advanced Research Projects Agency, the Office of Army Scientific Research, the Air Force Scientific Research Bureau, the National Foundation for Science and the National Aeronautics and Space Administration.
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