Alice & Bob Proposes Five-Criteria Framework for Evaluating Logical Qubits
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Off the Wire Press Releases PARIS, June 5, 2026 — Quantum computing company Alice & Bob has released a new five-criteria framework to define and benchmark logical qubits and establish a fair and comprehensive performance evaluation across hardware modalities. Logical qubits are a key milestone on the path to fault-tolerant quantum computing, but there is no industry-wide standard for defining, measuring or comparing them. Investors, analysts, enterprise decision-makers and researchers can use this new framework to objectively compare achievements from hardware with different levels of performance, maturity, and capability. The paper, Defining the Logical Qubit: Five Criteria to Benchmark Logical Qubit Claims, builds on a growing body of industry research to argue that a logical qubit should be defined strictly as a fundamental building block of a fault-tolerant quantum computer. It sets out five qualities a true logical qubit must demonstrate to be a credible candidate for scaling the technology. “Logical qubits are rapidly becoming the industry’s primary benchmark for progress toward fault-tolerant quantum computing, yet the term is used to describe achievements with vastly different levels of performance and capability,” said Jérémie Guillaud, VP Quantum Software, Alice & Bob. “Without a common benchmark, it’s difficult for the industry to compare approaches and evaluate genuine progress. At Alice & Bob, we believe a logical qubit should be more than an experimental demonstration – it should represent a fundamental building block of a fault-tolerant quantum computer. By proposing a clear definition and common set of criteria, we hope to make logical qubit claims more transparent, comparable, and easier to evaluate.” Alice & Bob’s five essential criteria to “score” logical qubit claims are: - Breakeven – Can you outperform your physical qubits? The logical qubit lifetime must exceed that of the physical qubits it is built from. - Scalable Parameters – Can you make it better? The error correction code has a parameter that can be tuned to lower the logical error rates. - Sufficient QEC Cycles – Have all the errors had time to happen? To measure the true logical error rate, the number of quantum error correction cycles must exceed the code distance. - Performance Across All Runs – Does it work without cherry-picking? Logical error rates are only meaningful if we can reproduce them during utility-scale computation, not just in experiments that rely on heavy post-selection. - Utility Timescales – Does error correction last the duration of the computation? A logical qubit must exhibit no logical error rates for the full duration of intended computations. Low-frequency errors are detected, not merely inferred from short benchmarking runs. The whitepaper can be downloaded here. “This is a strong, timely, and useful framework for cleaning up logical-qubit claims,” said Russ Fein, Managing Director, Corporate Fuel Partners. “It is especially valuable for investors and non-expert decision-makers because it provides a simple checklist for separating FTQC-relevant progress from weaker demonstrations.” About Alice & Bob Alice & Bob is a quantum computing company based in Paris and Boston whose goal is to create the first universal, fault-tolerant quantum computer. Advised by Nobel Prize winning researchers, Alice & Bob specializes in cat qubits, a technology developed by the company’s founders. Demonstrating the power of its cat architecture, Alice & Bob recently showed that it could reduce the hardware requirements for building a useful large-scale quantum computer up to 200 times compared with competing approaches. Source: Alice & Bob
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