New Device Can Take Photographs With a Single Atom

Researchers at Japan’s Institute for Molecular Science have built an “atom camera” that uses a single trapped rubidium-87 atom to map light patterns too small for conventional optical microscopes, publishing the work on 29 May in Nature Communications [1]. The device relies on an optical tweezer — a focused laser beam that immobilizes a single atom chilled to near absolute zero — to measure how the atom’s energy states shift when illuminated [1]. By dragging a light pattern across the stationary atom in 100-nanometer steps and recording either intensity or polarization at each position, the team assembles a two-dimensional map of the light field [1]. The approach can resolve features as small as 25 nm, below which quantum uncertainty begins to dominate [1]. Physicists have experimented with atoms as light probes since the 1990s, seeking to beat the diffraction limit that constrains traditional optics [1]. In 2022, groups at the University of California, Berkeley and the Institute of Photonic Sciences in Barcelona independently demonstrated rubidium-87 atoms capturing light intensity, with the Berkeley team reaching a resolution of 300 nm [1]. “We envisioned that the method could be made much more sensitive,” said Berkeley physicist Dan Stamper-Kurn, who was not involved in the new study [1]. The Okazaki group improved sensitivity by measuring a hyperfine transition — a far subtler energy shift than earlier efforts targeted — which also allowed them to record polarization alongside intensity [1]. The technique draws on the same optical-tweezer infrastructure already widespread in cold-atom laboratories. “There’s a lot of relevance to this, because these so-called optical tweezers are what we use in many experiments nowadays,” said Johannes Zeiher, a physicist at Ludwig-Maximilians-Universität München who was not part of the research [1]. The atom camera is being developed in parallel with the Okazaki team’s neutral-atom quantum computer, where optical tweezers hold rubidium qubits in a vacuum chamber [1]. Light beams used to control qubits often contain subtle polarization irregularities that can cause decoherence, and conventional cameras are difficult to deploy inside a vacuum without disturbing the atoms [1]. “Rather than bringing a camera from outside the vacuum chamber, why not use the tools already there inside our quantum playground in the vacuum?” said co-author Takafumi Tomita [1]. Kenji Ohmori, the lab’s lead physicist, said the group expects the atom camera “to serve as a valuable diagnostic tool for this effort in our laboratory, and in other similar efforts worldwide as well” [1]. The work extends a lineage of atomic-scale imaging that includes IBM’s 2013 stop-motion film “A Boy and His Atom,” which moved carbon monoxide molecules with a scanning tunneling microscope to create frames magnified 100 million times [2].