arXiv:2605.02389

Rethinking How to Act: Action-Space Engineering for Reinforcement Learning-Based Circuit Routing in Distributed Quantum Systems

Joost Van Veen, Luise Prielinger, Sebastian Feld

quant-phSubmitted May 4, 2026• Announced May 5, 2026• 0 citations

Abstract

As it becomes increasingly difficult to monolithically scale a quantum processor, distributed quantum computing (DQC) offers an alternative by distributing qubits across multiple smaller interconnected quantum processor modules. In such an architecture, the challenge of quantum circuit compilation shifts from placing and routing qubits within one module to placing, routing and using the qubits efficiently across modules. In order to optimize circuit execution time, the right state-dependent networking decisions must be found, such as when and where to generate shared remote quantum states to support remote operations. Reinforcement learning (RL) provides a natural framework for this problem, generating a compilation policy that can generalize across different circuits. Building on the framework of Promponas et al. (2024), we introduce an agent that combines a novel action-space formulation with effective action-masking strategies. A comprehensive numerical comparison of the two approaches under different coupling constraints shows that our agent achieves improved training and inference performance with a relative reduction in the modeled execution time of up to 35\%.

Comments: 10 pages, 12 figures

Related papers

Rethinking Quantum Circuit Optimization as a Reinforcement Learning Problem

Arjun Mehta, Sven Richter

Quantum circuit optimization is a foundational challenge in realizing practical quantum computation, requiring the reduction of gate counts and circuit depth while preserving logical equivalence across noisy intermediate-scale quantum (NISQ) devices. Conventional rule-based and heuristic compilation approaches demonstrate diminishing effectiveness as circuit complexity grows, motivating the search for adaptive, data-driven alternatives. This paper reformulates quantum circuit optimization as a Markov decision process (MDP), enabling deep reinforcement learning (RL) agents to autonomously discover efficient transformation strategies. A graph neural network (GNN)-based actor-critic architecture is developed to encode circuit topology and guide transformation selection. Drawing on empirical evidence from phase-structured quantum control tasks, neural feedback architectures, and convergence behavior in active learning agents, we demonstrate that the proposed framework achieves an average two-qubit gate count reduction of 31.4% and a circuit depth reduction of 27.8% across standard benchmark circuits, outperforming established compilation baselines. This work provides a principled theoretical foundation for the RL-as-optimizer paradigm and contributes an extensible experimental platform suited to NISQ-era constraints.

American Journal Of Big DataApr 1, 20260 citations

Quantum circuit optimization using deep reinforcement learning: Applications across multiple gate sets

Khoa Dang Tao, Sumin Jin, Muhammad Raza +1 more

The practical implementation of quantum algorithms on noisy intermediate-scale quantum devices encounters operational limitations due to decoherence and other sources of noise inherent in real hardware. To mitigate these errors while preserving the original functionality of the algorithm, shorter quantum circuits are therefore preferred. This motivates the development of effective quantum circuit optimization algorithms. Learning-based approaches have emerged as a leading candidate, yet existing autonomous agents remain inefficient, spending most of their training capacity rediscovering elementary reductions that deterministic rule-based methods already handle reliably. To address this challenge, we propose a reinforcement learning framework that embeds a deterministic Commutation-and-Reduction (CR) algorithm directly into the training environment. After every agent action, the CR algorithm automatically resolves elementary commutations and cancellations, enabling the agent to focus its learning capacity on the non-trivial optimizations where reinforcement learning adds real value. Empirical evaluation across two gate sets, the universal Clifford+T basis and the CNOT+Pauli basis, shows that RL+CR produces shorter circuits than a standard RL agent at all tested scales. We demonstrate that RL trained on smaller quantum circuits can be applied to larger quantum circuits. On 20-qubit Clifford+T circuits, five times larger than the training circuits, RL+CR removes twice as many gates as standard RL. This work provides a robust approach that could accelerate the compilation and optimization processes for future fault-tolerant and utility-scale quantum systems.

quant-pharXiv:2608.19103Aug 20, 20260 citations

Architecture-Aware Reinforcement Learning for Communication-Efficient Distributed Quantum Circuit Compilation

Chien-Tung Kuo, Felix Burt, Samuel Yen-Chi Chen +2 more

Distributed quantum computing provides a scalable route for executing quantum circuits beyond the capacity limits of a single quantum processing unit (QPU), but it introduces a communication-aware compilation problem involving strict hardware constraints and circuit dependencies. This paper presents an architecture-aware reinforcement-learning framework that formulates distributed quantum compilation as a constrained Markov Decision Process (MDP). The compiler-level communication actions dynamically update logical-qubit placement and enable subsequent gate execution. A heterogeneous graph model represents interactions among hardware, logical qubits, and circuit operations, while a policy trained via Proximal Policy Optimization optimizes EPR-pair consumption and communication makespan. Evaluation across benchmark circuits shows that our policy matches state-of-the-art heuristics on structured workloads, with lookahead reward shaping yielding modest improvements on unstructured circuits. These results demonstrate that reinforcement learning is a flexible alternative to manual heuristics, though scalability remains a key bottleneck for practical use.

quant-pharXiv:2608.06892Aug 10, 20260 citations

Deep Reinforcement Learning Strategies for Noise-Adaptive Qubit Routing

G. Indiveri A.M. Pascoal, João Paulo Fernandes, Rui Abreu

Qubit routing is the process of transforming quantum circuits to ensure that all two-qubit operations obey the connectivity constraints of a target architecture. The severe limitations of NISQ computers make qubit routing a vital compilation step. We propose a method to route quantum circuits based on deep reinforcement learning (RL). Moreover, we augment our approach with device calibration data to enable routing decisions based on the reliability of individual gates and we improve upon a previous technique for encoding circuits as a numerical matrix. We also implement enhancements such as BRIDGE operations, qubit embeddings, and commutation analysis. Using proximal policy optimization (PPO), we trained agents for five IBM topologies with between 5 and 27 qubits. For random circuits, the proposed strategy reduced the number of additional two-qubit gates by up to 37.3% and improved estimated success probability by up to 26.8% compared to the best algorithm from the Qiskit framework. For a dataset of realistic circuits, we achieved up to 27.5% and 15.2% improvements in gate count and circuit fidelity, respectively. We found no significant advantage from using calibration-aware models for IBM architectures, which deserves further exploration. Our work helps cement RL as a valuable qubit routing strategy, serving as another stepping stone toward practical applications for quantum computing.

IEEE International Conference on Quantum Software (QSW)Jul 7, 20243 citations

Distributed quantum architecture search using multi-agent reinforcement learning

Mikhail Sergeev, Georgii Paradezhenko, Daniil Rabinovich +1 more

Quantum architecture search (QAS) automates the design of parameterized quantum circuits for variational quantum algorithms. The framework finds a well-suited problem-specific structure of a variational ansatz. Among possible implementations of QAS the reinforcement learning (RL) stands out as one of the most promising. Current RL approaches are single-agent-based and show poor scalability with a number of qubits due to the increase of the action space dimension and the computational cost. We propose a novel multi-agent RL algorithm for QAS with each agent acting separately on its own block of a quantum circuit. This procedure allows to significantly accelerate the convergence of the RL-based QAS and reduce its computational cost. We benchmark the proposed algorithm on MaxCut problem on 3-regular graphs and on ground energy estimation for the Schwinger Hamiltonian. In addition, the proposed multi-agent approach naturally fits into the set-up of distributed quantum computing, favoring its implementation on modern intermediate scale quantum devices.

quant-pharXiv:2511.22708Dec 1, 20250 citations

Using Reinforcement Learning to find Efficient Qubit Routing Policies for Deployment in Near-term Quantum Computers

Steven Herbert, Akash Sengupta

This paper addresses the problem of qubit routing in first-generation and other near-term quantum computers. In particular, it is asserted that the qubit routing problem can be formulated as a reinforcement learning (RL) problem, and that this is sufficient, in principle, to discover the optimal qubit routing policy for any given quantum computer architecture. In order to achieve this, it is necessary to alter the conventional RL framework to allow combinatorial action space, and this represents a second contribution of this paper, which is expected to find additional application, beyond the qubit routing problem addressed herein. Numerical results are included demonstrating the advantage of the RL-trained qubit routing policy over using a sorting network.

arXiv:1812.11619Dec 30, 201822 citations