Programmable Light. Could Ultra Cold Atoms Provide a Substrate For Quantum Computing

Controlling atoms with light opens exciting possibilities for new technologies, and researchers are now demonstrating unprecedented control over individual atoms using a novel platform. Guoqing Wang, David C. Spierings, and Matthew L. Peters, all from the MIT-Harvard Center for Ultracold Atoms, alongside colleagues, have successfully created programmable scattering of light using just a few individual atoms held within a ring of light. The team achieves this by precisely positioning atoms and cooling them to near their lowest energy state, enabling highly directional scattering and the creation of narrow, well-defined beams of light. This breakthrough represents a significant step towards building programmable optical devices and exploring new avenues in quantum computation, offering a pathway to manipulate light and matter at the most fundamental level.

By integrating tweezer arrays with a high-cooperativity ring cavity exhibiting chiral atom-cavity coupling, researchers demonstrate highly directional Bragg scattering from a programmable number of atoms. Through accurate control of the interatomic distance, they observe a narrowing of the scattered light signal as the number of atoms increases incrementally. This new approach allows for precise manipulation and observation of atomic interactions within a controlled environment.

Cesium Atom Array Phonon Occupation Measurements

This supplemental material provides detailed supporting information for research on collective scattering of light from cold Cesium atoms trapped in an optical cavity. Measurements of the collective scattering rate from two-atom arrays, performed on resonance, and with blue and red sideband excitation, allow researchers to extract the mean phonon occupation of the radial motion, demonstrating the effectiveness of cavity cooling. Spectra of collective scattering from different numbers of atoms, taken at specific atom separations, reveal clear evidence of collective interference effects. Theoretical analyses address the potential for incoherence in collective scattering due to the multi-level nature of Cesium atoms, tracing over atomic states to account for entanglement between scattered light and the atoms.

The team concludes that this incoherence is likely a small effect in their experiment. A detailed theoretical analysis of the spectrum of collective scattering considers the interplay between atomic transition frequencies, the cavity resonance, and collective interference effects. Theoretical estimations of the cooling limit of the radial motion calculate the minimum phonon occupation achievable with the cavity cooling setup, considering cavity cooperativity and probe beam polarization, validating the cooling process. This comprehensive material addresses potential criticisms and provides a thorough justification for the conclusions presented in the main research paper. By integrating tweezer arrays with a specialized ring cavity, they achieved strong coupling between the atoms and light, enabling unprecedented control over light scattering direction. This innovative setup allows researchers to precisely control the distance between atoms, observing a narrowing of the scattered light signal as more atoms are added to the array, confirming the system’s ability to manipulate collective atomic behavior. A key achievement was cooling the atoms to extremely low temperatures, reducing their motion to near its minimum quantum state.

This precise temperature control is crucial for minimizing disturbances and maximizing the coherence of the light scattering process. The team demonstrated that this level of control enables the creation of highly defined light patterns, opening possibilities for advanced optical devices and quantum technologies. The ability to manipulate light scattering in this way represents a significant step towards programmable photonics, where light can be shaped and directed with atomic-level precision. Furthermore, the research reveals that the system’s performance is limited only by the precision of the atomic positioning and temperature control.

Measurements of the atomic temperature confirmed that the observed scattering behavior is consistent with theoretical predictions, validating the experimental approach. The demonstrated level of control over atomic interactions and light scattering has significant implications for various fields, including the development of advanced optical sensors, quantum simulators, and novel computing architectures. By precisely controlling the arrangement and interaction of atoms, researchers can create custom optical elements and explore new ways to manipulate light for technological advancements.

Chiral Cavities Control Single Atom Scattering

This research successfully integrates optical tweezers with a specially designed ring cavity to investigate how light interacts with small numbers of atoms. Researchers demonstrate highly directional light scattering from individual and small arrays of atoms, observing interference patterns that narrow as more atoms are added, consistent with Bragg scattering even when atoms are relatively far apart. The system achieves precise control over atom positioning and cools the atoms to extremely low temperatures, approximately 2 μK, using the properties of the cavity itself. Furthermore, the team observed asymmetric interference in the cavity modes, governed by the arrangement of the atoms, and demonstrated directional light scattering from a single atom within the chiral cavity, breaking time-reversal symmetry in the light-matter interaction. This platform offers sub-nanometer precision in measuring atomic separation and opens avenues for exploring quantum chiral optics, including non-Hermitian interactions and symmetry-breaking phenomena. The cavity cooling technique, independent of atomic structure, may also be applicable to a wide range of particles, including ions, molecules, and nanoparticles.