arXiv subjects

Amin Taherkhani

Publications and source records attributed to Amin Taherkhani.

5 recordsLinked to original sources

arXiv2026

Performance Analysis of QAOA Across Distributed Quantum Network Topologies Using SwitchQNet

Quantum data-center (QDC) architectures aim to scale distributed quantum computing (DQC) by interconnecting multiple quantum processing units (QPUs), but their performance depends strongly on how algorithmic communication patterns interact with entanglement generation, switch reconfiguration, and network topology. This paper studies the Quantum Approximate Optimization Algorithm (QAOA) as a graph-structured optimization workload for QDC-based distributed quantum computing. We adapt QAOA to SwitchQNet, a distributed quantum compiler framework that schedules communication and entanglement generation over switch-based QDC networks, by adding a routing generator that converts graph-dependent two-qubit cost interactions into remote-CX communication requests across QPUs. Using this extension, we evaluate QAOA instances across Clos, fat-tree, and spine-leaf topologies, measuring communication latency, EPR-pair overhead, EPR wait time, retry overhead, and sensitivity to buffer size, look-ahead depth, communication-qubit count, EPR latency, and EPR fidelity assumptions. The results show that QAOA obtains modest but consistent latency reductions, highlighting its value as a diagnostic benchmark for studying the interaction between algorithm structure, entanglement management, and quantum-network architecture.

quant-ph↗

arXiv2026

A Distributed Switching Protocol for Quantum Networks

With the advent of the construction and deployment of entanglement-based quantum networks, the efficient use of network resources will become a critical challenge for the scalable operation of such a system. Recently, architectures that incorporate memoryless optical switches have gained attention for forwarding entangled photons. By leveraging these architectures, costly resources such as high efficiency Bell State Analyzers (BSAs) can be shared across the network. Nevertheless, the introduction of switching substantially complicates the process of multiplexing and resource allocation compared to an individual link. In this work, we propose a switching protocol for unbuffered, multidrop quantum networks in a photonic synchronization domain that establishes a link between two end nodes using a shared BSA in the switched network. To achieve this, two end nodes cooperatively select the target BSA node with the lowest path cost and independently reserve each path within the network. Bi-path reservations are performed to allocate resources in a distributed manner. The proposed protocol is evaluated through simulation on Q-Fly network topologies under varying traffic conditions. The results demonstrate high link establishment success with stable performance even under increased network load. These capabilities which are driven by our proposed protocol are an essential way to realize large-scale, managed, and automated quantum networks.

quant-ph↗

arXiv2025

Q-Fly: An Optical Interconnect for Modular Quantum Computers

Much like classical supercomputers, scaling up quantum computers requires an optical interconnect. However, signal attenuation leads to irreversible qubit loss, making quantum interconnect design guidelines and metrics different from conventional computing. Inspired by the classical Dragonfly topology, we propose a multi-group structure where the group switch routes photons emitted by computational end nodes to the group's shared pool of Bell state analyzers (which conduct the entanglement swapping that creates end-to-end entanglement) or across a low-diameter path to another group. We present a full-stack analysis of system performance, a combination of distributed and centralized protocols, and a resource scheduler that plans qubit placement and communications for large-scale, fault-tolerant systems. We implement a prototype three-node switched interconnect to justify hardware-side scalability and to expose low-level architectural challenges. We create two-hop entanglement with fidelities of 0.6-0.76. Our design emphasizes reducing network hops and optical components to simplify system stabilization while flexibly adjusting optical path lengths. Based on evaluated loss and infidelity budgets, we find that moderate-radix switches enable systems meeting expected near-term needs, and large systems are feasible. Our design is expected to be effective for a variety of quantum computing technologies, including ion traps and neutral atoms.

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arXiv2025

Automatic Configuration Protocols for Optical Quantum Networks

Before quantum networks can scale up to practical sizes, there are many deployment and configuration tasks that must be automated. Currently, quantum networking testbeds are largely manually configured: network nodes are constructed out of a combination of free-space and fiber optics before being connected to shared single-photon detectors, time-to-digital converters, and optical switches. Information about these connections must be tracked manually; mislabeling may result in experimental failure and protracted debugging sessions. In this paper, we propose protocols and algorithms to automate two such manual processes. First, we address the problem of automatically identifying connections between quantum network nodes and time-to-digital converters. Then, we turn to the more complex challenge of identifying the nodes attached to a quantum network's optical switches. Implementation of these protocols will help enable the development of other protocols necessary for quantum networks, such as network topology discovery, link quality monitoring, resource naming, and routing. We intend for this paper to serve as a roadmap for near-term implementation.

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arXiv2024

Optimal Switching Networks for Paired-Egress Bell State Analyzer Pools

To scale quantum computers to useful levels, we must build networks of quantum computational nodes that can share entanglement for use in distributed forms of quantum algorithms. In one proposed architecture, node-to-node entanglement is created when nodes emit photons entangled with stationary memories, with the photons routed through a switched interconnect to a shared pool of Bell state analyzers (BSAs). Designs that optimize switching circuits will reduce loss and crosstalk, raising entanglement rates and fidelity. We present optimal designs for switched interconnects constrained to planar layouts, appropriate for silicon waveguides and Mach-Zehnder interferometer (MZI) $2 \times 2$ switch points. The architectures for the optimal designs are scalable and algorithmically structured to pair any arbitrary inputs in a rearrangeable, non-blocking way. For pairing $N$ inputs, $N(N - 2)/4$ switches are required, which is less than half of number of switches required for full permutation switching networks. An efficient routing algorithm is also presented for each architecture. These designs can also be employed in reverse for entanglement generation using a shared pool of entangled paired photon sources.

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