Search
Menu

Optical Clock Uses Laser Tweezers to Manipulate Atoms

Facebook X LinkedIn Email
BOULDER, Colo., Sept. 20, 2019 — JILA physicists have demonstrated a new atomic clock design that uses laser tweezers to trap, control, and isolate atoms. The tweezers are created by an IR laser beam aimed through a microscope. The beam is deflected to create 10 spots of light for trapping individual strontium atoms. The traps are refilled every few seconds from a prechilled cloud of atoms overlapped with the tweezer light.

The atoms held by the tweezers are excited by a laser that is stabilized by a silicon crystal cavity, creating a "clock laser" light. This light is applied perpendicular to the tweezer light along with an applied magnetic field. Nondestructive imaging reveals whether the atoms are ticking properly; the atoms will emit light only when in the lower-energy state.

The tweezer clock traps and controls atoms individually to maintain ticking stability. It can reuse the same atoms many times without needing to constantly reload new ones. “The tweezer design addresses various issues with other atomic clocks,” physicist Adam Kaufman said. “Using our technique, we can hold onto atoms and reuse them for as long as 16 seconds, which improves the duty cycle — the fraction of time spent using the atoms’ ticking to correct the laser frequency — and precision.”

Too many atoms in the system can lead to collisions that destabilize the clock. To eliminate unnecessary atoms, the researchers apply a pulse of light to create weakly bound molecules, which break apart and escape the trap. The tweezer site is then left either empty or with only one atom. Having at most one atom per site keeps the ticking stable for longer periods of time. Also, the tweezer clock can isolate a single atom in a trap site very quickly, thereby reducing interference and providing a more stable signal over time.

In experiments, the researchers observed coherence times of 3.4 seconds and duty cycles up to 96% through repeated interrogation. The tweezer clock requires little downtime to prepare new atoms. The atoms are well isolated to be less likely to interfere with one another.

NIST researchers develop atomic clock design that uses laser tweezers to control atoms. Pictured, physicist Adam Kaufman.
JILA/NIST physicist Adam Kaufman adjusts the setup for a laser that controls and cools the strontium atoms in the optical tweezer clock. The atoms are trapped individually by 10 tweezers — laser light focused into tiny spots — inside the square orange container behind Kaufman's left hand. Courtesy of Burrus/NIST.


The tweezer clock can provide the strong signals and stability of a multiatom lattice clock. “The tweezer design’s long-term promise as a competitive clock is rooted in its unique balancing of these capabilities,” Kaufman said. 


The laser tweezers offer pinpoint control, allowing the researchers to vary the spacing between atoms and tweak their quantum properties. The tweezers can be used to excite the atoms so their electrons are more weakly bound to the nucleus. In this “fluffy” state, the atoms can be trapped in magnetic spin-up and spin-down states more easily, and become entangled through spin exchange. Quantum states such as entanglement could improve measurement sensitivity and thus enhance clock precision.

The National Institute of Standards and Technology (NIST) team is helping to prepare for the future international redefinition of the second, which has been based on the cesium atom since 1967. The team now plans to build a larger clock and formally evaluate its performance using more tweezers and atoms, with a target of about 150 atoms. Kaufman also plans to add entanglement, which could improve clock sensitivity and performance and, in a separate application, perhaps provide a new platform for quantum computing and simulation.

The research was published in Science (https://doi.org/10.1126/science.aay0644).   

Published: September 2019
Glossary
optical tweezers
Optical tweezers refer to a scientific instrument that uses the pressure of laser light to trap and manipulate microscopic objects, such as particles or biological cells, in three dimensions. This technique relies on the momentum transfer of photons from the laser beam to the trapped objects, creating a stable trapping potential. Optical tweezers are widely used in physics, biology, and nanotechnology for studying and manipulating tiny structures at the microscale and nanoscale levels. Key...
optical clock
An optical clock is a highly precise and advanced timekeeping device that relies on the oscillations of electromagnetic radiation in the optical or ultraviolet part of the electromagnetic spectrum. Unlike traditional atomic clocks, which use microwave frequencies, optical clocks operate at much higher frequencies, typically involving transitions in atoms or ions at optical wavelengths. Optical clocks have the potential to provide unprecedented accuracy and stability in timekeeping. Key points...
atomic clock
An atomic clock is a highly precise timekeeping device that uses the vibrations or oscillations of atoms as a reference for measuring time. The most common type of atomic clock uses the vibrations of atoms, typically cesium or rubidium atoms, to define the length of a second. The principle behind atomic clocks is based on the fundamental properties of atoms, which oscillate at extremely stable and predictable frequencies. The primary concept employed in atomic clocks is the phenomenon of...
metrology
Metrology is the science and practice of measurement. It encompasses the theoretical and practical aspects of measurement, including the development of measurement standards, techniques, and instruments, as well as the application of measurement principles in various fields. The primary objectives of metrology are to ensure accuracy, reliability, and consistency in measurements and to establish traceability to recognized standards. Metrology plays a crucial role in science, industry,...
quantum optics
The area of optics in which quantum theory is used to describe light in discrete units or "quanta" of energy known as photons. First observed by Albert Einstein's photoelectric effect, this particle description of light is the foundation for describing the transfer of energy (i.e. absorption and emission) in light matter interaction.
quantum entanglement
Quantum entanglement is a phenomenon in quantum mechanics where two or more particles become correlated to such an extent that the state of one particle instantly influences the state of the other(s), regardless of the distance separating them. This means that the properties of each particle, such as position, momentum, spin, or polarization, are interdependent in a way that classical physics cannot explain. When particles become entangled, their individual quantum states become inseparable,...
astronomy
The scientific observation of celestial radiation that has reached the vicinity of Earth, and the interpretation of these observations to determine the characteristics of the extraterrestrial bodies and phenomena that have emitted the radiation.
Research & TechnologyAmericasNISTJILANational Institute of Standards and TechnologyLasersLight Sourcesoptical tweezersOpticsoptical clockatomic clockmetrologyTest & Measurementpulsed lasersquantum opticsquantum entanglementastronomy

We use cookies to improve user experience and analyze our website traffic as stated in our Privacy Policy. By using this website, you agree to the use of cookies unless you have disabled them.