Ordered Atom Arrays Unlock New Forms of Collective Light Emission

Alec Douglas and colleagues at Harvard University have developed a platform where collective emission extends beyond single modes, emerging instead from a network of photon-mediated interactions. The work reveals strong super- and subradiant emission in two-dimensional atom arrays, alongside spatial correlations that confirm the transformation of cooperative decay into a strongly correlated many-body process. These findings offer a programmable system for exploring dissipative many-body quantum physics and potential advances in photonics and quantum entanglement.

Direct observation of excited atoms reveals collective quantum behaviour

A quantum gas microscope was employed to directly observe the excited state of individual atoms within carefully crafted, two-dimensional arrays. This technique represents a significant advancement in observing collective quantum phenomena. Utilising single-site imaging, the method circumvents limitations inherent in detecting weakly emitted light, particularly from subradiant states where emission is non-directional; it directly measures which atoms remain excited instead of counting photons. Traditional methods relying on photon detection struggle with the inherently weak signals from subradiant states, where atoms do not radiate efficiently. By directly imaging the atomic population, researchers can bypass this limitation and gain a complete picture of the system’s evolution. Removing all ground-state atoms with a resonant laser pulse isolated atoms in excited states for imaging, achieving high-fidelity measurement of population and spatial coherence. This isolation process ensures that only the initially excited atoms contribute to the observed dynamics, minimising noise and improving the accuracy of the measurements. The resonant laser pulse selectively removes atoms in the ground state, leaving a clear signal from the excited atoms.

This approach provides a new method for studying quantum phenomena at the atomic level, offering a more comprehensive understanding of light-matter interactions. The system comprised 500 atoms initially prepared in an excited state, evolving for approximately 20 microseconds, allowing observation of super- and subradiance phenomena. This timescale is crucial, as it allows sufficient time for the collective effects to manifest themselves while remaining within the coherence time of the atomic ensemble. Detailed characterisation of collective atomic behaviour is now possible with this new approach, revealing spatial and phase correlations previously hidden from traditional detection methods. A quantum gas microscope imaged individual atoms in a two-dimensional array with subwavelength spacing of 266 nanometres, offering unprecedented resolution. This resolution is critical for resolving the near-field interactions between atoms, which are essential for observing strong collective effects. The ability to image individual atoms with such precision opens up new possibilities for studying quantum many-body systems.

Subwavelength atomic arrays demonstrate correlated decay and emergent spin textures

Subwavelength atomic array construction has been demonstrated at a lattice spacing of 266nm, a five-fold improvement over previous work limited to 841nm wavelengths. This unprecedented proximity, less than half the wavelength of emitted light, enables strong, near-field interactions between atoms, previously unattainable due to the diffraction limit. The diffraction limit traditionally restricts the ability to manipulate and observe objects smaller than approximately half the wavelength of light. By operating in the subwavelength regime, these arrays overcome this limitation and unlock new possibilities for controlling light-matter interactions. The resulting two-dimensional arrays exhibit both strong superradiant and subradiant emission, creating a novel regime for manipulating light-matter interactions; superradiance intensifies light release, while subradiance suppresses it. Superradiance arises from the collective emission of photons, resulting in a significantly enhanced emission rate. Conversely, subradiance involves the suppression of emission due to destructive interference between atoms. Repeated bursts of intensified light emission, known as superradiant revivals, confirmed extensive scaling of superradiance within the 266nm lattice. These revivals demonstrate the robustness of the superradiant effect and its ability to persist over multiple cycles of excitation and decay.

Site-resolved imaging revealed a transition from ferromagnetic to antiferromagnetic spin textures, directly demonstrating the transformation of cooperative decay into a strongly correlated many-body process and opening avenues for programmable quantum systems. Ferromagnetic arrangements exhibit aligned atomic spins, while antiferromagnetic arrangements show opposing alignments, directly linking cooperative decay to complex many-body interactions. The observed transition between these spin textures provides evidence for the emergence of collective behaviour and the breakdown of independent atomic behaviour. Furthermore, the two-dimensional arrays support both superradiant and subradiant emission, with the latter acting as potential channels for long-lived photon storage. Subradiant states offer a promising pathway for storing quantum information, as the suppressed emission rate extends the lifetime of the stored photons. This control over light emission represents a new programmable platform for quantum physics exploration, potentially enabling advances in photon capture and atom-photon entanglement, although maintaining coherence and scalability beyond these initial arrays remains a key hurdle to realising practical quantum technologies. Achieving long coherence times and scaling up the number of atoms in the array are crucial steps towards building functional quantum devices.

Subwavelength atomic arrays enable enhanced light-matter interaction

David Hunger and his colleagues are building increasingly precise control over the fundamental interactions between light and matter, a pursuit vital for advances in quantum computing and sensing. Achieving this control demands overcoming inherent limitations in how atoms are arranged and how they collectively respond to light, as previous experiments struggled with spatial constraints and the inability to observe subtle correlations. The ability to precisely control the arrangement of atoms and their interactions with light is essential for developing new quantum technologies. While demonstrating impressive subwavelength atomic spacing, this new work currently focuses on establishing the platform’s capabilities rather than delivering practical applications like efficient photon storage. The initial focus is on validating the platform and demonstrating its potential for exploring fundamental quantum phenomena.

It is important to acknowledge that these arrays are presently a proof of concept and not yet a functioning quantum device. Constructing two-dimensional atom arrays with gaps smaller than the wavelength of light unlocks a new regime of collective atomic behaviour. This precise geometrical ordering, achieved with a spacing of 266 nanometres, enables strong interactions between atoms mediated by photons, interactions normally limited by the diffraction limit. Both superradiance, an intensified release of light, and subradiance, a suppression of light emission, were directly observed within these arrays. Site-resolved imaging revealed a transition between ferromagnetic and antiferromagnetic spin textures, demonstrating that cooperative decay transforms into a complex, many-body process. The ability to observe and control these collective effects opens up new possibilities for exploring fundamental quantum phenomena and developing new quantum technologies.

Researchers demonstrated a new platform using two-dimensional atom arrays with 266 nanometre spacing to control interactions between light and matter. This precise arrangement allows for the observation of strong superradiant and subradiant emission, revealing how collective atomic behaviour transitions into a complex, many-body process. The team directly observed spatial correlations and distinct spin textures, confirming the platform’s ability to explore fundamental quantum physics. They intend to further validate this programmable platform and investigate its potential for manipulating photon capture and atom-photon entanglement.