Quantum Transduction: Enabling Quantum Networking

TL;DR

This work addresses the hardware-driven heterogeneity in quantum networks by reframing quantum transduction as a communications-engineering problem. It distinctively formulates two operation modes, Direct Quantum Transduction (DQT) and Entanglement Generation Transduction (EGT), and develops a taxonomy of network archetypes for transmitting quantum information via teleportation. The analysis emphasizes how conversion efficiency $\eta$, cooperativity $C$, and extraction ratios $\zeta_x$ govern performance, deriving capacity thresholds for DQT on qubits vs ebits, and showing that EGT often relaxes hardware requirements while enabling robust entanglement distribution. By mapping transduction to a modular block in a quantum system model and exploring intra-band and multi-node scenarios, the paper lays a foundational framework for designing scalable quantum networks and advancing distributed quantum computing. The practical impact lies in guiding transducer integration into repeaters and network stacks, fostering architectures that balance hardware feasibility with quantum communication reliability.

Abstract

The complementary features of different qubit platforms for computing and communicating impose an intrinsic hardware heterogeneity in any quantum network, where nodes, while processing and storing quantum information, must also communicate through quantum links. Indeed, one of the most promising hardware platforms at quantum node scale for scalable and fast quantum computing is the superconducting technology, which operates at microwave frequencies. Whereas, for communicating at distances of practical interest beyond few meters, quantum links should operate at optical frequencies. Therefore, to allow the interaction between superconducting and photonic technologies, a quantum interface, known as quantum transducer, able to convert one type of qubit to another is required. This paper aims to provide a tutorial treatise on the fundamental research challenges of quantum transduction. The tutorial is structured around a communications engineering framework, thereby shedding light on its fundamental role in quantum network design and deployment- a perspective often overlooked in existing literature. This framework allows us to categorize different transduction modalities and to reveal an unorthodox one where the transducer itself can act as an entanglement source. From this standpoint, it is possible to conceive different source-destination link archetypes, where transduction plays a crucial role in the communication performances. The analysis also translates the quantum transduction process into a proper functional block within a new communication system model for a quantum network.

Figures (12)

• Figure 1: Schematic representation of a quantum transducer as an interface between superconducting quantum nodes and optical quantum links. As highlighted within the figure, the frequency gap between microwave and optical frequencies spans five orders of magnitude, making the transduction between the two hardware platforms one of the most challenging nowadays LauSinBar-20.
• Figure 2: Paper Structure.
• Figure 3: Schematic representation of the interconnection of two superconducting quantum nodes via Direct Quantum Transduction (DQT), converting either informational qubits or ebits. Microwave (optical) qubit and ebit are depicted in blue (red).
• Figure 4: Some key literature highlighting the major advancements and milestones in microwave-optical quantum transduction.
• Figure 5: Conversion efficiency $\eta$ as a function of cooperativity $C$ and the product of extraction ratios $\zeta_o\zeta_m$.

Theorems & Definitions (3)

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