A Carbon-Aware Quantum Computing Framework for LCA-Driven Sustainability in Quantum Cloud Services

As quantum computing transitions from laboratory experiments to cloud-based services, understanding its environmental impact is critical. Unlike classical computing, which is primarily operational-carbon-dominated, the environmental footprint of quantum systems remains poorly characterized. This study conducts a cradle-to-grave life cycle assessment (LCA) of a 100-logical-qubit superconducting quantum platform. The authors extend the existing Carbon-Aware Quantum Computing (CQC) framework to a service-level model, allowing Quantum Cloud Service (QCS) providers to allocate environmental burdens to specific jobs and identify actionable sustainability levers.

The study reveals that superconducting quantum computers are structurally embodied-carbon-dominated, with production, delivery, and end-of-life phases accounting for 77.3% to 85.2% of the total five-year footprint. Operational-embodied parity—the point where energy consumption equals the initial manufacturing burden—is not reached for 17 to 28 years, compared to just 2.7 years for classical high-performance computing. Because the power draw of cryogenic systems is largely load-independent (the cryostat and compressors run continuously regardless of computational activity), the carbon intensity per job is heavily dependent on how much work is performed over the platform's lifetime.

The findings invert traditional sustainability intuition. For QCS providers, the most impactful levers are:

1. Utilization: Increasing platform occupancy yields the largest carbon reduction (up to 19.7x), as it amortizes the fixed manufacturing burden across more computational tasks.
2. Service Life Extension: Keeping hardware in service longer (e.g., 10 years vs. 3 years) provides a 59.9% reduction in carbon intensity.
3. Electricity Supply: While important, siting in low-carbon regions offers less leverage (6.5x) than utilization or life extension because the embodied carbon remains a constant, unavoidable baseline.

Operational efficiency and carbon-aware scheduling, while standard in classical cloud sustainability, offer limited benefits for these quantum systems unless they are combined with strategies that allow for hardware to be powered down entirely.

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