Single atom works as a camera to image light below the diffraction limit

Jun 30, 2026

A new atom camera uses one ultracold rubidium atom to map light intensity and polarization with spatial resolution below 100 nanometers.

(Nanowerk News) Researchers in Japan have turned a single, ultracold atom into a camera that images light at scales far smaller than ordinary optical microscopes can resolve. The team at the Institute for Molecular Science, part of the National Institutes of Natural Sciences, calls the method the “Atom Camera.” A single atom records both the brightness and the polarization of a light field with a spatial resolution below 100 nanometers, a level of detail relevant to quantum computing hardware.

Key Findings

The work was led by Assistant Professor Takafumi Tomita and Professor Kenji Ohmori. They trapped one rubidium atom in an optical tweezer, a tightly focused laser beam that pulls particles toward its brightest point. The technique was invented by Arthur Ashkin in the 1970s and can hold individual atoms. Rubidium is an alkali metal with atomic number 37, carrying a single electron in its outermost (5s) orbital. The results appeared in Nature Communications (“Atom camera: super-resolution scanning microscope of a light pattern with a single ultracold atom”). . Conceptual illustration of the Atom Camera. A single ultracold rubidium (Rb) atom trapped in an optical tweezer is spatially scanned to visualize the intensity and polarization distributions of a light pattern. (Image: NIMS) The atom was held near absolute zero, the lowest temperature physically possible, defined as 0 Kelvin or minus 273.15 degrees Celsius. At that temperature its motion drops to the smallest amount quantum mechanics allows. To reach this state, the team used laser cooling, which uses laser light to slow atomic motion and bring the atom to the lowest motional state available inside the tweezer. Quantum computers and related technologies rely heavily on precisely shaped light. Lasers are a primary tool for controlling the quantum states of matter, and arrays of tiny light spots and lattice-shaped patterns are central to running neutral-atom quantum computers, which use individual atoms held in place by lasers as their quantum bits. Checking those light patterns is awkward in practice. The patterns form inside sealed equipment such as vacuum chambers, and placing a conventional camera inside risks disturbing the qubits, which react strongly to environmental noise. Observing the light from outside through lenses brings its own problem: the lenses introduce aberrations, distortions that blur or warp the measured pattern.

How a single atom images light below the diffraction limit

The atom itself solves both problems by serving as the probe. The researchers moved the trapped atom through the light field with nanometer-scale precision and measured how the light shifted the energy of the atom’s internal spin states. Each position yielded local information about the light at that exact spot. Assembling these readings across many positions reconstructed the intensity distribution of the light. The same spin-dependent energy shift also responds to polarization, the direction in which a light wave oscillates. Light can oscillate in a fixed direction, called linear polarization, or rotate as it travels, called circular polarization. The team used the spin shift to map polarization directly. As a test, they examined a tightly focused laser beam confined to a region roughly one micrometer wide. Even a simple linearly polarized beam picks up circular polarization structures near its focal point after passing through a lens, and the Atom Camera captured this subtle structure. Resolution in this approach is set by the residual quantum jitter in the atom’s position rather than by the wavelength of light. The atom’s positional fluctuation was about 25 nanometers under the experimental conditions, and the team demonstrated an overall resolution below 100 nanometers. Standard optical microscopes cannot clearly resolve features much smaller than the wavelength of the light they use, a fundamental ceiling known as the diffraction limit, which this method surpassed. The Atom Camera offers a route to directly observe nanoscale optical structures that have been hard to reach with existing tools. Because the behavior of atomic qubits depends on both laser intensity and laser polarization, a single method that measures the two at once is a useful diagnostic for neutral-atom quantum computers and simulators, which arrange atoms with lasers and exploit their interactions to model complex quantum systems that conventional computers struggle to calculate. The study involved the Institute for Molecular Science, Hamamatsu Photonics Central Research Laboratory, and RIKEN. By reading out the fine structure of light fields from inside the very devices that use them, the method gives developers of atom-based quantum hardware a way to see and correct the laser patterns their machines depend on.