Atoms are notoriously tough to manage. They zigzag like fireflies, tunnel out of the strongest containers and jitter even at temperatures close to absolute zero.
Nonetheless, scientists must lure and manipulate single atoms to ensure that quantum units, akin to atomic clocks or quantum computer systems, to function correctly. If particular person atoms will be corralled and managed in massive arrays, they will function quantum bits, or qubits — tiny discrete items of data whose state or orientation might ultimately be used to hold out calculations at speeds far larger than the quickest supercomputer.
Researchers on the Nationwide Institute of Requirements and Know-how (NIST), along with collaborators from JILA — a joint institute of the College of Colorado and NIST in Boulder — have for the primary time demonstrated that they will lure single atoms utilizing a novel miniaturized model of “optical tweezers” — a system that grabs atoms utilizing a laser beam as chopsticks.
Ordinarily, optical tweezers, which garnered the 2018 Nobel Prize in Physics, characteristic cumbersome centimeter-size lenses or microscope aims exterior the vacuum holding particular person atoms. NIST and JILA have beforehand used the approach with nice success to create an atomic clock.
Within the new design, as a substitute of typical lenses, the NIST crew used unconventional optics — a sq. glass wafer about 4 millimeters in size imprinted with tens of millions of pillars just a few a whole lot of nanometers (billionths of a meter) in peak that collectively act as tiny lense. These imprinted surfaces, dubbed metasurfaces, focus laser mild to lure, manipulate and picture particular person atoms inside a vapor. The metasurfaces can function within the vacuum the place the cloud of trapped atoms is positioned, in contrast to atypical optical tweezers.
The method entails a number of steps. First, incoming mild that has a very easy kind, often known as a airplane wave, strikes teams of the tiny nanopillars. (Airplane waves are like shifting parallel sheets of sunshine which have a uniform wavefront, or part, whose oscillations stay in sync with one another and neither diverge nor converge as they journey.) The groupings of nanopillars remodel the airplane waves right into a collection of little wavelets, every of which is barely out of sync with its neighbor. Because of this, adjoining wavelets attain their peak at barely completely different occasions.
These wavelets mix or “intrude” with one another, inflicting them to focus all their power at a particular place — the placement of the atom that’s to be trapped.
Relying on the angle at which the incoming airplane waves of sunshine strike the nanopillars, the wavelets are targeted at barely completely different locations, enabling the optical system to lure a collection of particular person atoms that reside at barely completely different areas from one another.
As a result of the mini flat-lenses will be operated inside a vacuum chamber and require no shifting elements, the atoms will be trapped with out having to construct and manipulate a posh optical system, stated NIST researcher Amit Agrawal. Different researchers at NIST and JILA have beforehand used typical optical tweezers with nice success to design atomic clocks.
Within the new research, Agrawal and two different NIST scientists, Scott Papp and Wenqi Zhu, together with collaborators from Cindy Regal’s group at JILA, designed, fabricated and examined the metasurfaces and carried out single-atom trapping experiments.
In a paper printed as we speak in PRX Quantum, the researchers reported that that they had individually trapped 9 single rubidium atoms. The identical approach, scaled up by utilizing a number of metasurfaces or one with massive discipline of view, ought to be capable of confine a whole lot of single atoms, Agrawal stated, and will prepared the ground to routinely lure an array of atoms utilizing a chip-scale optical system .
The system holds the atoms in place for about 10 seconds, which is lengthy sufficient to review the quantum mechanical properties of the particles and use them to retailer quantum data. (Quantum experiments function on time scales of ten millionths to thousandths of a second.)
To display that they captured the rubidium atoms, the researchers illuminated them with a separate mild supply, inflicting them to fluoresce. The metasurfaces then performed a second crucial function. Initially, that they had formed and targeted the incoming mild that trapped the rubidium atoms. Now the metasurfaces captured and targeted the fluorescent mild emitted by these similar atoms, redirecting the fluorescent radiation right into a digicam with a purpose to picture the atoms.
The metasurfaces can do extra than simply confine single atoms. By focusing mild with pinpoint accuracy, the metasurfaces can coax particular person atoms into particular quantum states, tailor-made for particular atom-trapping experiments.
For instance, polarized mild directed by the tiny lenses could cause an atom’s spin — a quantum attribute analogous to the Earth spinning on its axis — to level in a specific course. These interactions between targeted mild and single atoms are helpful for a lot of sorts of atomic-scale experiments and units, together with future quantum computer systems.
Paper: T.-W. Hsu, W. Zhu, T. Thiele, MO Brown, SB Papp, A. Agrawal and CA Regal. Single atom trapping in a metasurface lens optical tweezer. PRX Quantum. Revealed on-line 1 August 2022. DOI: 10.1103/PRXQuantum.3.030316.