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arXiv:2601.14845 · Quantum Science and Technology

Combatting noise in near-term quantum data centres

Kenny Campbell, Ahmed Lawey, Mohsen Razavi

quant-phSubmitted Jan 21, 2026• Announced Jan 22, 2026• 0 citations
v1 · Jan 21, 2026v2 · Oct 7, 2026
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Abstract

We analyse the performance of different error handling methods in the quantum data centre paradigm of distributed quantum computing. We compare the impact of quantum error detection, using the three-qubit repetition code and the [[4, 1, 2]] Leung-Nielsen-Chuang-Yamamoto code, on remote gates with that of conventional entanglement distillation techniques. Detailed classical simulation is used to obtain results for realistic near-term hardware.

Journal reference
Quantum Science and Technology, 11, 045011 (2026)
DOI
10.1088/2058-9565/ae978f
Comments
13 pages, 8 figures

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We analyse the performance of different error handling methods in the quantum data centre paradigm of distributed quantum computing. We compare the impact of quantum error detection, using the three-qubit repetition code and the [[4, 1, 2]] Leung-Nielsen-Chuang-Yamamoto code, on remote gates with that of conventional entanglement distillation techniques. Detailed classical simulation is used to obtain results for realistic near-term hardware.
Distributed quantum computing is a promising way of overcoming the scalability challenges of quantum computers, but establishing quantum links over large distances remains difficult. Therefore, in this thesis, we explore quantum data centres (QDCs), in which multiple quantum processing units (QPUs) are housed together within the same warehouse and linked together over short links. By considering such a setting, we avoid the challenges of long-distance quantum communications while retaining the scalability of distributed architectures. We focus primarily on understanding and quantifying the role of noise in QDCs. We compare the impact of different types of noise in the QDC setting and explore various types of inter-QPU gate. Both individual inter-QPU gates and an assortment of larger distributed quantum circuits are investigated. Based on our findings, we evaluate strategies for the handling of noise, considering both quantum error detection and entanglement distillation based solutions. We also provide a preliminary investigation into the use of QDCs for generating entangled resource states suitable for quantum communications or measurement based quantum computing applications. A major contribution of this thesis is the development of a novel simulation framework for distributed quantum computing, which formed the basis of many of the results obtained. The framework enables users to easily specify distributed quantum circuits or import circuits designed for a single-QPU and convert them to a distributed circuit. Many of the complications of interpreting a distributed quantum circuit, such as the management of communication qubits are also handled automatically. Moreover, the framework's built-in interpreter can interpret common building blocks of distributed quantum computing, such as inter-QPU gates.
Quantum error detection can produce unbiased expectation values that exponentially converge to noiseless results as the code distance is increased. Despite this, its performance as an error mitigation technique is relatively understudied on quantum hardware because of its two main drawbacks: (i) the number of samples increases exponentially in the circuit depth/noise level, and (ii) the classical processing generally grows exponentially in the code distance, though exceptions exist. Additionally, the constant (but often large) overhead of embedding the code and logical operations on hardware can make accuracy worse instead of better. In this work, we seek to provide a clear picture of these opportunities and challenges for scaling quantum error detection on hardware. We do so by performing a detailed benchmarking study on real and simulated noisy quantum computers, using the repetition code and triangular color code for memory experiments and logical computations with up to 747474 physical qubits. In addition to these benchmarks, we estimate the pseudothreshold of codes to map the frontier of error detection on current and future quantum computers. Despite the challenges, our results show strong promise for scaling quantum error detection on hardware.
Quantum computers connected through classical and quantum communication channels can be combined to function as a single unit to run large quantum circuits that each device is unable to execute on their own. The distributed quantum computing paradigm is therefore often seen as a potential pathway to scaling quantum computing to capacities necessary for practical and large-scale applications. Whether connecting multiple quantum processing units (QPUs) in clusters or over networks, quantum communication requires entanglement to be generated and distributed over distances. Using entanglement, the remote CX protocol can be performed, which allows the application of the CX gate involving qubits located in different QPUs. In this work, we use a specialized simulation framework for a high-level evaluation of the impact of the protocol when executed under noise in various network configurations using different number of QPUs. We compare naive and graph partitioning qubit assignment strategies and how they affect the fidelity in experiments run on Grover, GHZ, VQC, and random circuits. The results provide insights on how QPU and network configurations or naive scheduling can degrade performance.
Abstract Quantum data centres (QDCs) could overcome the scalability challenges of modern quantum computers. Single-processor monolithic quantum computers are affected by increased cross talk and difficulty of implementing gates when the number of qubits is increased. In a QDC, multiple quantum processing units (QPUs) are linked together over short distances, allowing the total number of computational qubits to be increased without increasing the number of qubits on any one processor. In doing so, the error incurred by operations at each QPU can be kept small, however additional noise will be added to the system due to the latency cost and errors incurred during inter-QPU entanglement distribution. We investigate the relative impact of these different types of noise using a classically simulated QDC with two QPUs and compare the robustness to noise of the two main ways of implementing remote gates, cat-comm and TP-comm. We find that considering the quantity of gates or inter-QPU entangled links is often inadequate to predict the output fidelity from a quantum circuit and infer that an improved understanding of error propagation during distributed quantum circuits may represent a significant optimisation opportunity for compilation.
In the distributed quantum computing paradigm, well-controlled few-qubit 'nodes' are networked together by connections which are relatively noisy and failure prone. A practical scheme must offer high tolerance to errors while requiring only simple (i.e. few-qubit) nodes. Here we show that relatively modest, three-qubit nodes can support advanced purification techniques and so offer robust scalability: the infidelity in the entanglement channel may be permitted to approach 10% if the infidelity in local operations is of order 0.1%. Our tolerance of network noise is therefore an order of magnitude beyond prior schemes, and our architecture remains robust even in the presence of considerable decoherence rates (memory errors). We compare the performance with that of schemes involving nodes of lower and higher complexity. Ion traps, and NV-centres in diamond, are two highly relevant emerging technologies: they possess the requisite properties of good local control, rapid and reliable readout, and methods for entanglement-at-a-distance.
Building fault-tolerant quantum computers with large numbers of logical qubits requires both scalable hardware architectures and error-correcting codes that make efficient use of physical qubits. Photonic interconnects address both of these challenges by allowing the physical qubits to be distributed across multiple processors while providing the non-local connectivity necessary to implement resource-efficient codes such as high-rate quantum low-density parity-check (qLDPC) codes. A key requirement for realising this architecture is the ability to perform stabiliser measurements between remote processors, which has not previously been demonstrated experimentally. Here we report the first experimental demonstration of distributed quantum error detection and correction. We generate entanglement between network qubits in two separate trapped-ion processors and use it to perform remote syndrome measurements on data qubits. We first realise a distributed [[2, 1, 1]] repetition code, detecting phase-flip errors on a logical qubit encoded across the two modules in real time and suppressing logical errors. We then combine these mid-circuit syndrome measurements with real-time feedforward to actively correct arbitrary single-qubit Pauli errors on a distributed Bell state. These results provide an experimental foundation for quantum error correction (QEC) across modular quantum architectures.