A research group led by Assistant Professor Takafumi Tomita and Professor Kenji Ohmori at the Institute for Molecular Science, National Institutes of Natural Sciences, has developed a new microscopy technique called the “Atom Camera,” which uses a single ultracold atom at near absolute zero temperature*1 trapped in an optical tweezer*2 as a camera to visualize the intensity and polarization*3 distributions of light at the nanometer (one-millionth of a millimeter) scale.
In this study, a single atom trapped by an optical tweezer was successfully utilized as a scanning probe*4 for imaging the fine structures of intensity and polarization distributions of light patterns with a spatial resolution beyond the diffraction limit*5 of conventional optical microscopes.
The results were published in the online edition of the British scientific journal Nature Communications on May 29th, 2026.
1. Research background
In recent years, quantum computers and other quantum technologies have been rapidly advancing worldwide. Precise control of finely structured light fields widely used in such quantum technologies is critically important. In particular, laser light is one of the primary tools for controlling quantum states of matter, exemplified by the arrays of microscopic light spots and lattice-shaped light patterns created by lasers playing central roles in operating neutral-atom quantum computers*6.
To properly control such finely structured laser fields generated by optical devices, it is necessary to directly observe the light patterns formed inside quantum devices such as vacuum chambers. However, it is difficult to place diagnostic cameras inside vacuum chambers without affecting qubits, which are highly sensitive to environmental noises. In addition, when light is observed remotely through lenses, aberrations*7 introduced by those lenses themselves are most likely to distort the measured light patterns.
2. Research results
The researchers used a single rubidium*8 atom trapped in an optical tweezer as a probe. By spatially scanning the atom position with nanometer-scale (one-millionth of a millimeter) precision and measuring the energy shifts of its internal spin states, they obtained local information about the light field at each atom position. From the measured energy shifts as a function of the atom position, the intensity distribution of the light was successfully visualized (Fig. 2).
Furthermore, the researchers focused on the fact that the spin-dependent energy shift depends not only on light intensity, but also on light polarization. Utilizing this property, they successfully visualized polarization distributions directly. As a demonstration of this technique for polarization imaging, they observed a non-trivial polarization structure appearing in a tightly focused laser beam confined within a spatial extent approximately 1 micrometer (one-thousandth of a millimeter) wide. It is known that even a simple linearly polarized laser beam acquires circular polarization structures near the focal point after passing through a lens. The Atom Camera directly visualized this non-trivial polarization structure (Fig. 2).
The probe atom used in this method was cooled down with a method called laser cooling*9 to the lowest quantum-mechanical motional state achievable inside the optical tweezer. The spatial resolution of the probe is fundamentally determined by the quantum-mechanical positional fluctuation of a single atom, which was approximately 25 nanometers under the present experimental conditions. The researchers experimentally demonstrated a spatial resolution below 100 nanometers, significantly surpassing the diffraction limit of conventional optical microscopy.
3. Future development and social significance of this research
The Atom Camera developed in this study provides a new measurement technique for directly observing nanoscale optical structures that have been difficult to access by conventional methods.
Techniques capable of precisely characterizing microscopic light fields are expected to be useful for emerging neutral-atom quantum computers and simulators*10 in characterizing and controlling the structures of laser fields used to manipulate atoms. In particular, because the behavior of atomic qubits depends not only on laser intensity, but also on laser polarization, the ability to simultaneously measure both of them makes this method a powerful diagnostic tool.
4. Terminology
1* Optical Tweezer
A technique that traps microscopic particles using tightly focused laser light. Invented by Arthur Ashkin in the 1970s, optical tweezers can trap individual atoms by attracting them toward the brightest region of the focused laser beam.
2* Absolute Zero Temperature
The temperature at which atomic and molecular motion reaches its minimum possible value. This temperature is defined as 0 Kelvin, corresponding to −273.15°C.
3* Polarization
A property describing the oscillation direction of light waves. Light can oscillate in a fixed direction (linear polarization) or rotate while propagating (circular polarization). In this study, the researchers visualized distributions of circular polarization.
4* Probe
A sensor or detection element used to investigate a target system. In this study, a single atom itself was used as the probe to obtain local information about the light field.
5* Diffraction Limit
Because light behaves as a wave, conventional optical microscopes cannot clearly resolve structures smaller than approximately the wavelength of light. This fundamental resolution limit is called the diffraction limit.
6* Neutral-Atom Quantum Computer
A modality of quantum computing hardware that uses neutral atoms trapped and arranged in space by optical tweezers as quantum bits (qubits). This approach has rapidly been attracting worldwide attention because it offers several advantages, including room-temperature operation, flexible atom transport, scalability, and long coherence times.
7* Aberration
A phenomenon in which light passing through a lens fails to focus ideally, causing image blur or distortion in optical systems such as cameras and microscopes.
8* Rubidium Atom
An alkali metal atom with atomic number 37. It has one electron in the 5th orbital (5s) around the nucleus.
9* Laser Cooling
A technique that uses laser light to reduce the motion of atoms and cool them to extremely low temperatures. By suppressing the thermal motion of atoms, laser cooling enables high-precision quantum control and precision measurements.
10* Neutral-Atom Quantum Simulator
A device that artificially arranges neutral atoms trapped by laser light and uses their quantum interactions to emulate complex quantum phenomena such as magnetism and correlated electron systems, which are difficult to calculate using conventional computers.
