InterQnet: A Heterogeneous Full-Stack Approach to Co-designing Scalable Quantum Networks

Abstract

Quantum communications have progressed significantly, moving from a theoretical concept to small-scale experiments to recent metropolitan-scale demonstrations. As the technology matures, it is expected to revolutionize quantum computing in much the same way that classical networks revolutionized classical computing. Quantum communications will also enable breakthroughs in quantum sensing, metrology, and other areas. However, scalability has emerged as a major challenge, particularly in terms of the number and heterogeneity of nodes, the distances between nodes, the diversity of applications, and the scale of user demand. This paper describes InterQnet, a multidisciplinary project that advances scalable quantum communications through a comprehensive approach that improves devices, error handling, and network architecture. InterQnet has a two-pronged strategy to address scalability challenges: InterQnet-Achieve focuses on practical realizations of heterogeneous quantum networks by building and then integrating first-generation quantum repeaters with error mitigation schemes and centralized automated network control systems. The resulting system will enable quantum communications between two heterogeneous quantum platforms through a third type of platform operating as a repeater node. InterQnet-Scale focuses on a systems study of architectural choices for scalable quantum networks by developing forward-looking models of quantum network devices, advanced error correction schemes, and entanglement protocols. Here we report our current progress toward achieving our scalability goals.

Figures (16)

• Figure 1: Organization of the InterQnet project, highlighting our systems approach to scalable quantum networks. The approach integrates devices, error correction methods, protocols, architectures, and simulation/experimentation into two co-design/integration cycles.
• Figure 2: An entanglement-centric, hourglass-like view of quantum networking. This abstraction is provided for illustrative purposes and will not be evaluated in this work.
• Figure 3: Three-node heterogeneous quantum network consisting of trapped ytterbium (Yb) atoms, erbium (Er$^{3+}$) ions in solids, and superconducting quantum devices ($\mu$Wave). BSM, the Bell state measurement, includes a 50/50 beam splitter and a pair of single-photon detectors. (a) Array of trapped Yb atoms with the relevant level structure for controlling optical clock qubits and nuclear qubits. AOD is an acousto-optics deflector. (b) Energy-level structure of the Er$^{3+}$ qubit in a magnetic field with cavity-enhanced transition A. Also shown is an optical image of an array of photonic crystal cavities that host Er$^{3+}$ ions in a TiO$_2$ thin film on a silicon-on-insulator (SOI) wafer. (c) Schematics of the upper panel, a single-electron qubit trapped on a solid neon surface (green) strongly interacting with a superconducting resonator (yellow), and lower panel, an integrated quantum transducer consisting of a piezo-optomechanical microwheel resonator strongly coupled with a superconducting Ouroboros resonator. (d) Schematic of pulse shaping using a quantum frequency converter (QFC) followed by BSM. Table \ref{['tab:devices']} summarizes the current development status of our devices.
• Figure 4: (a) Pauli checks forming distance-2 code. Red checks can be applied recursively. (b) Noisy simulation for different levels of recursion: rec0 represents no red gates; rec1 represents adding ancillas $a_3$ and $a_4$ and the supported red gates to the rec0 circuit; rec2 corresponds to adding ancillas $a_5$ and $a_6$ and the supported red gates to the rec1 circuit.
• Figure 5: (a) Quantum error detection for novel entanglement distillation protocol that can distill two Bell pairs from four imperfect ones. (b) Quantum error correction with concatenated bosonic GKP code and qLDPC code. (c) Efficient and robust purification of logical Bell pairs with qLDPC codes.