Coherent interaction of atoms with a beam of light confined in a light cage
Flavie Davidson-Marquis, Julián Gargiulo, Esteban Gómez-López, Bumjoon Jang, Tim Kroh, Chris Müller, Mario Ziegler, Stefan Alexander Maier, Harald Kübler, Markus Alexander Schmidt, Oliver J. Benson
Controlling coherent interaction between optical fields and quantum systems in scalable, integrated platforms is essential for quantum technologies. Miniaturised, warm alkali-vapour cells integrated with on-chip photonic devices represent an attractive system, in particular for delay or storage of a single-photon quantum state. Hollow-core fibres or planar waveguides are widely used to confine light over long distances enhancing light-matter interaction in atomic-vapour cells. However, they suffer from inefficient filling times, enhanced dephasing for atoms near the surfaces, and limited light-matter overlap. We report here on the observation of modified electromagnetically induced transparency for a non-diffractive beam of light in an on-chip, laterally-accessible hollow-core light cage. Atomic layer deposition of an alumina nanofilm onto the light-cage structure was utilised to precisely tune the high-transmission spectral region of the light-cage mode to the operation wavelength of the atomic transition, while additionally protecting the polymer against the corrosive alkali vapour. The experiments show strong, coherent light-matter coupling over lengths substantially exceeding the Rayleigh range. Additionally, the stable non-degrading performance and extreme versatility of the light cage provide an excellent basis for a manifold of quantum-storage and quantum-nonlinear applications, highlighting it as a compelling candidate for all-on-chip, integrable, low-cost, vapour-based photon delay.
Controlling coherent interaction between optical fields and quantum systems in scalable, integrated platforms is essential for quantum technologies. Miniaturised, warm alkali-vapour cells integrated with on-chip photonic devices represent an attractive system, in particular for delay or storage of a single-photon quantum state. Hollow-core fibres or planar waveguides are widely used to confine light over long distances enhancing light-matter interaction in atomic-vapour cells. However, they suffer from inefficient filling times, enhanced dephasing for atoms near the surfaces, and limited light-matter overlap. We report here on the observation of modified electromagnetically induced transparency for a non-diffractive beam of light in an on-chip, laterally-accessible hollow-core light cage. Atomic layer deposition of an alumina nanofilm onto the light-cage structure was utilised to precisely tune the high-transmission spectral region of the light-cage mode to the operation wavelength of the atomic transition, while additionally protecting the polymer against the corrosive alkali vapour. The experiments show strong, coherent light-matter coupling over lengths substantially exceeding the Rayleigh range. Additionally, the stable non-degrading performance and extreme versatility of the light cage provide an excellent basis for a manifold of quantum-storage and quantum-nonlinear applications, highlighting it as a compelling candidate for all-on-chip, integrable, low-cost, vapour-based photon delay.
Quantum memories are essential for photonic quantum technologies, enabling long-distance quantum communication and serving as delay units in quantum computing. Hot atomic vapors using electromagnetically induced transparency provide a simple platform with second-long photon storage capabilities. Light-guiding structures enhance performance, but current hollow-core fiber waveguides face significant limitations in filling time, physical size, fabrication versatility, and large-scale integration potential. In this work, we demonstrate the storage of attenuated coherent light pulses in a cesium (Cs) quantum memory based on a 3D-nanoprinted hollow-core waveguide, known as a light cage (LC), with several hundred nanoseconds of storage times. Leveraging the versatile fabrication process, we successfully integrated multiple LC memories onto a single chip within a Cs vapor cell, achieving consistent performance across all devices. We conducted a detailed investigation into storage efficiency, analyzing memory lifetime and bandwidth. These results represent a significant advancement toward spatially multiplexed quantum memories and have the potential to elevate memory integration to unprecedented levels. We anticipate applications in parallel single-photon synchronization for quantum repeater nodes and photonic quantum computing platforms.
Quantum memories are essential for photonic quantum technologies, enabling long-distance quantum communication and serving as delay units in quantum computing. Hot atomic vapors using electromagnetically induced transparency provide a simple platform with second-long photon storage capabilities. Light-guiding structures enhance performance, but current hollow-core fiber waveguides face significant limitations in filling time, physical size, fabrication versatility, and large-scale integration potential. In this work, we demonstrate the storage of attenuated coherent light pulses in a cesium (Cs) quantum memory based on a 3D-nanoprinted hollow-core waveguide, known as a light cage (LC), with several hundred nanoseconds of storage times. Leveraging the versatile fabrication process, we successfully integrated multiple LC memories onto a single chip within a Cs vapor cell, achieving consistent performance across all devices. We conducted a detailed investigation into storage efficiency, analyzing memory lifetime and bandwidth. These results represent a significant advancement toward spatially multiplexed quantum memories and have the potential to elevate memory integration to unprecedented levels. We anticipate applications in parallel single-photon synchronization for quantum repeater nodes and photonic quantum computing platforms.
Quantum memories are essential for photonic quantum technologies, enabling long-distance quantum communication and serving as delay units in quantum computing. Hot atomic vapors using electromagnetically induced transparency provide a simple platform with second-long photon storage capabilities. Light-guiding structures enhance performance, but current hollow-core fiber waveguides face significant limitations in filling time, physical size, fabrication versatility, and large-scale integration potential. In this work, we demonstrate the storage of attenuated coherent light pulses in a cesium (Cs) quantum memory based on a 3D-nanoprinted hollow-core waveguide, known as a light cage (LC), with several hundred nanoseconds of storage times. Leveraging the versatile fabrication process, we successfully integrated multiple LC memories onto a single chip within a Cs vapor cell, achieving consistent performance across all devices. We conducted a detailed investigation into storage efficiency, analyzing memory lifetime and bandwidth. These results represent a significant advancement toward spatially multiplexed quantum memories and have the potential to elevate memory integration to unprecedented levels. We anticipate applications in parallel single-photon synchronization for quantum repeater nodes and photonic quantum computing platforms.
Low-light-level optical nonlinearities are of significant interest for performing operations such as single-photon switching and quantum non-demolition measurements on single-photons. To evoke strong nonlinearities from singlephotons, one can enhance the matter-photon interaction using strongly nonlinear materials such as alkali vapors in combination with an appropriate geometry such as a waveguide, which provides a long interaction length while maintaining a small light mode area. We demonstrate for the first time that such a system can be experimentally realized by loading rubidium vapor inside a hollow-core photonic band-gap fiber. Using the technique of light-induced atomic desorption in this geometry, we have generated optical depths greater than 1000. As a proof of principle, we demonstrate electromagnetically induced transparency (EIT) with control powers 1000 times lower than those used for hot vapor cells in a focused beam geometry. Working with such a high aspect ratio geometry requires us to identify and measure the various sources of decoherence via spectroscopy of desorbed atoms in the fiber. Using such techniques, we also estimate the temperature of the desorbing atoms inside the fiber. The desorption mechanism is studied, and we show that pulsed desorption beams of the right amplitude and duration can be used for generating precisely controlled optical depths. Finally, we investigate the use of various buffer gas techniques for increasing the effective transverse path of the atoms as they move across the fiber in order to reduce their ground state decoherence and map this effect as a function of buffer gas pressure.
Quantum information networks will facilitate the use of a broad range of quantum technologies including quantum computers, quantum sensors, and quantum communication systems, among others. An important component of these networks are devices that enable light-atom interactions, as they interface photons from communication channels with the matter-based nodes, allowing for processing of photonic quantum information. These devices will need to be scalable and easily integrated to expand the size of networks. One platform of interest is vapour-filled hollow-core fibres (HCF). By overlapping light and atomic vapour within the same volume, strong interactions can occur, including important nonlinear effects such as cross-phase modulation and wave mixing processes. HCFs can be directly integrated into fibre systems, making them a convenient technology for the expansion of quantum networks. This thesis reports on three projects themed around scalable technologies for quantum networks. The first project involved the injection-locking of a diode laser. Nanosecond long pulses had their 20 GHz frequency chirps reduced to near the Fourier-transform limit, enabling them to interact efficiently with rubidium vapour. This project demonstrated that the mature, cost effective, and scalable technology of diode lasers can be compatible with essential atomic ensemble quantum networking devices such as quantum memories and quantum frequency converters. In the second project, a high-bandwidth quantum memory protocol called off-resonant cascaded absorption (ORCA) was investigated. The ORCA memory can be used to synchronise high speed photonic operations that occur in optical quantum information processing. This project used a Kagom´e HCF to enhance the light-atom interactions, resulting in two orders of magnitude reduction in optical power requirements. The third project again used the HCF platform, this time to facilitate a quantum frequency conversion scheme that converts rubidium-compatible, near-IR wavelengths to the telecommunications C-band, which is ideal for long distance fibre transmission. This project demonstrated the FWM process has reduced optical pump powers and higher efficiency in the HCF when compared to a rubidium-filled cell. The research described in this thesis presents a strong argument for the use of HCFs as a scalable technology that could be implemented in quantum networks.
Atomic vapors of alkali metals are widely used to slow and stop light in tabletop experiments. In order to take advantage of the underlying quantum interference effects in future commercial devices, highly reactive alkali atoms must be incorporated into small volumes with integrated optical access. With integration in mind, we describe the development of a hollow-core waveguide technology based on the combination of vapor-filled hollow waveguides and conventional solid-core waveguides on a silicon chip. We discuss the underlying principles of the waveguide design, the development of different approaches to building on-chip vapor cells, the demonstration of linear and nonlinear rubidium spectroscopy on a chip, and the prospects for quantum interference effects such as slow light and giant Kerr nonlinearities using this approach. Ultrasmall active vapor volumes on the order of 100 picoliters with simultaneously high optical density in excess of two illustrate the potential of planar hollow-core waveguides for linear and nonlinear optical spectroscopy of atoms confined on a chip.