Multi-partite entanglement is fundamental to emerging quantum technologies, such as quantum networks, which ultimately require devices with strong light–matter interactions and long coherence times. Here, we introduce nanobeam photonic crystal cavities combining both extreme quality factors (∼107) with sub-wavelength field confinement to reach unprecedented light–matter interactions. Operating at 780 nm, our devices are tailored for efficient coupling and entanglement with ultracold 87Rb atoms, a key ingredient in quantum networks due to their hyperfine structure. Our new designs also facilitate the precise optical trapping of atoms, and we demonstrate coherent entanglement generation between them, which is remarkably resilient to atomic displacements. These platforms can be easily scaled-up to extremely large quantum networks, for distributed quantum computing and future light-based quantum technologies.
Multi-partite entanglement is fundamental to emerging quantum technologies, such as quantum networks, which ultimately require devices with strong light–matter interactions and long coherence times. Here, we introduce nanobeam photonic crystal cavities combining both extreme quality factors (∼107) with sub-wavelength field confinement to reach unprecedented light–matter interactions. Operating at 780 nm, our devices are tailored for efficient coupling and entanglement with ultracold 87Rb atoms, a key ingredient in quantum networks due to their hyperfine structure. Our new designs also facilitate the precise optical trapping of atoms, and we demonstrate coherent entanglement generation between them, which is remarkably resilient to atomic displacements. These platforms can be easily scaled-up to extremely large quantum networks, for distributed quantum computing and future light-based quantum technologies.
New paradigms for optical physics emerge with lattices of atoms trapped in one and two-dimensional photonic crystals [1-4]. Exemplary experimental platforms include photonic crystal waveguides [5-7] and cavities [8, 9]. Owing to their small optical loss and tight field confinement, these nanoscale dielectric devices are capable of mediating long-range atom-atom interactions using photons propagating in their guided modes. In a complimentary fashion, long-range interactions between photons can be mediated by an underlying lattice of atoms. Such systems have the potential to provide new tools for scalable quantum networks, quantum phases of light and matter, and quantum metrology. However, bringing this future of atom nanophotonics to fruition requires the creation of an interdisciplinary toolkit for the control, manipulation, and interaction of atoms and photons with a complexity and scalability not currently possible. I will give an overview of the theoretical prospects for new physics and review experimental progress in this nascent field at the interfaces of nano-photonics, atomic physics, and quantum optics.
Underlying matter and light are their building blocks of tiny atoms and photons. The ability to control and utilize matter-light interactions down to the elementary single atom and photon level at the nano-scale opens up exciting studies at the frontiers of science with applications in medicine, energy, and information technology. Of these, an intriguing front is the development of quantum networks where N >> 1 single-atom nodes are coherently linked by single photons, forming a collective quantum entity potentially capable of performing quantum computations and simulations. Here, a promising approach is to use optical cavities within the setting of cavity quantum electrodynamics (QED). However, since its first realization in 1992 by Kimble et al., current proof-of-principle experiments have involved just one or two conventional cavities. To move beyond to N >> 1 nodes, in this thesis we investigate a platform born from the marriage of cavity QED and nanophotonics, where single atoms at ~100 nm near the surfaces of lithographically fabricated dielectric photonic devices can strongly interact with single photons, on a chip. Particularly, we experimentally investigate three main types of devices: microtoroidal optical cavities, optical nanofibers, and nanophotonic crystal based structures. With a microtoroidal cavity, we realized a robust and efficient photon router where single photons are extracted from an incident coherent state of light and redirected to a separate output with high efficiency. We achieved strong single atom-photon coupling with atoms located ~100 nm near the surface of a microtoroid, which revealed important aspects in the atom dynamics and QED of these systems including atom-surface interaction effects. We present a method to achieve state-insensitive atom trapping near optical nanofibers, critical in nanophotonic systems where electromagnetic fields are tightly confined. We developed a system that fabricates high quality nanofibers with high controllability, with which we experimentally demonstrate a state-insensitive atom trap. We present initial investigations on nanophotonic crystal based structures as a platform for strong atom-photon interactions. The experimental advances and theoretical investigations carried out in this thesis provide a framework for and open the door to strong single atom-photon interactions using nanophotonics for chip-integrated quantum networks.
A coherent interface between optical photons and long-lived matter qubits can form the basis for a broad range of quantum technologies. I will describe the realization of such an interface using inversion-symmetric color-centers integrated into diamond nanophotonic devices at millikelvin temperatures. The resulting high-cooperativity spin-photon interface can be fabricated en-masse and exhibits a unique combination of long coherence times, high-fidelity control, strong light-matter interactions, and efficient photon out-coupling, establishing it as a leading platform for the construction of a large-scale quantum internet.
High Resolution Image Download MS PowerPoint Slide Spin-based, quantum-photonics promise to realize distributed quantum computing and quantum networks. The performance depends on an efficient entanglement distribution where cavity quantum electrodynamics could boost the efficiency. The central challenge is the development of compact devices with large spin-photon coupling rates and a high operation bandwidth. Photonic crystal cavities comprise strong field confinement but require highly accurate positioning of atomic systems in mode field maxima. Negatively charged silicon-vacancy centers in diamond emerged as promising atom-like systems. Spectral stability and access to long-lived, nuclear-spin memories enabled elementary demonstrations of quantum network nodes, including memory-enhanced quantum communication. In a hybrid approach, we deterministically place SiV-containing nanodiamonds inside one hole of one-dimensional, freestanding, Si 3 N 4 -based photonic crystal cavities and coherently couple individual optical transitions to cavity modes. We optimize light–matter coupling utilizing two-mode composition, waveguiding, Purcell-enhancement, and cavity-resonance tuning. The resulting photon flux increases by 14 compared to free space. Corresponding lifetime-shortening below 460 ps puts potential operation bandwidth beyond GHz rates.
Neutral atom arrays have emerged as one of the leading platforms for quantum computation and simulation. Integrating these arrays with photonic interfaces, such as optical cavities, enables high-speed qubit readout, efficient atom-photon entanglement, and novel quantum simulation capabilities through long-range interactions. However, achieving scalable and efficient integration of atom arrays with photonic structures remains a significant challenge. In this work, we present an atom-array cavity-array platform that integrates cesium atom arrays with a photonic chip containing over 100 nanophotonic cavities. This platform inherently supports multiplexing by allowing simultaneous interactions between multiple atoms and multiple cavities, a crucial capability for scaling up quantum information processing and networking. To enable this integration, we develop three key techniques: (1) a backgroundfree imaging scheme utilizing excited-state transitions in cesium with fidelity exceeding 99%, (2) a photonic chip design optimized for efficient atom loading, and (3) a free-space coupling scheme achieving over 65% waveguide-to-fiber coupling efficiency. We demonstrate collisional blockade-limited loading of atom arrays near the photonic chip, parallel transport of atoms to multiple cavities, a key capability that enables the multiplexing required in quantum networks and distributed quantum computing. Finally, we show an array of resonant telecom cavities, and multiple theoretical architectures to make use of these to distribute entanglement across hundreds of kilometers. These results address critical challenges in atom-photon integration and pave the way for scalable quantum information processing.
Quantum technologies are widely expected to bring a revolution in communications and information technologies in the coming decade allowing, for example, un-paralleled levels of secure communications. For quantum communication, photonic quantum effects have played a central role, but most photonic solutions and systems based on light-matter interaction also require cryogenic environments. Strong coupling of light and matter at the single emitter level is a fundamental quantum resource offering deterministic energy exchange between single photons and a two-level system, and the possibility to achieve single-photon nonlinearities via the anharmonicity of the Jaynes-Cummings ladder. Until recently, however, the conditions for achieving strong-coupling were most commonly met at cryogenic temperatures such that de-coherence processes are suppressed. As a major step forward, we have recently demonstrated room-temperature strong coupling of single molecules [1] and single quantum dots [2] to ultra-confined light fields in plasmonic resonators at ambient conditions. The fact that strong-coupling conditions may be reached at room temperature is of immense interest because it represents a clear route to a practical implementation and use of quantum behaviour in nanophotonic systems and its application in bio-sensing [3]. The talk will discuss how nanoplasmonics can be an enabler of ultrafast room-temperature quantum nanophotonic networks via strong coupling and ultrafast quantum dynamics [4]. We will highlight the physics associated with recently demonstrated room-temperature strong coupling of single molecules in a plasmonic nano-cavity [1] and near-field generated strong coupling of single quantum dots [2] and single quantum emitter Dicke enhancement [5] paving the road towards single-photon quantum nonlinearities. The presentation will also explain near-field enhanced single-photon emission in near-zero index materials [6] and ultrafast multi-partite quantum entanglement [7]. This provides the foundation for unprecedented control over photon number, single photon dynamics, and dynamic multi-photon coherence. These properties are all imperative for the development of next-generation, nanoscale building blocks in ambient-temperature photonic quantum communication technologies.