THE QUANTUM INTELLIGENCER

Record-Breaking 120-Qubit GHZ State Creation Using Optimized Compilation and Error Detection in Superconducting Quantum Hardware Summary: This preprint reports the creation of the largest GHZ (Greenberger-Horne-Zeilinger) state to date, consisting of 120 superconducting qubits, representing a significant milestone in quantum computing hardware capabilities. The researchers achieved this breakthrough through a combination of optimized compilation techniques, low-overhead error detection, and temporary uncomputation methods. They employed an automated compiler specifically designed to maximize error detection in state preparation circuits while accommodating arbitrary qubit connectivity constraints and variations in error rates across the quantum processor. The team measured a GHZ fidelity of 0.56(3) with a post-selection rate of 28%, demonstrating genuine multipartite entanglement across all 120 qubits. The fidelity was certified using multiple equivalent methods, providing robust verification of the quantum state's quality. This achievement advances the frontier of controllable quantum systems and represents important progress toward practical applications requiring large-scale entanglement. Key Points: - Created the largest GHZ state to date using 120 superconducting qubits - Used optimized compilation, error detection, and temporary uncomputation techniques - Developed automated compiler for maximizing error detection in state preparation circuits - Achieved GHZ fidelity of 0.56(3) with 28% post-selection rate - Certified fidelity using multiple equivalent verification methods - GHZ states (Schrödinger cat states) are benchmarks for quantum hardware quality - High sensitivity to noise makes large GHZ states difficult to prepare - Technique accommodates arbitrary qubit connectivity constraints and error rate variations Notable Quotes: - "Entanglement is the quintessential quantum phenomenon and a key enabler of quantum algorithms." - "The ability to faithfully entangle many distinct particles is often used as a benchmark for the quality of hardware and control in a quantum computer." - "GHZ states, also known as Schrödinger cat states, are useful for this task. They are easy to verify, but difficult to prepare due to their high sensitivity to noise." Data Points: - 120 qubits in the GHZ state (largest to date) - GHZ fidelity: 0.56(3) (where 3 represents the uncertainty) - Post-selection rate: 28% - Submission date: October 10, 2025 - arXiv identifier: 2510.09520v1 Controversial Claims: - The paper does not contain particularly controversial claims, as it primarily reports experimental results rather than speculative theories. The claims are supported by empirical data and multiple verification methods. The assertion that this represents the "largest GHZ state prepared to date" is a factual claim based on current experimental capabilities in the field. Technical Terms: - GHZ states (Greenberger-Horne-Zeilinger states) - Schrödinger cat states - Superconducting qubits - Quantum entanglement - Error detection - Optimized compilation - Temporary uncomputation - Qubit connectivity constraints - Fidelity measurement - Post-selection - Multipartite entanglement - Quantum state preparation - Decoherence - Quantum algorithms Content Analysis: This paper presents a landmark experimental achievement in quantum computing: the creation of the largest GHZ (Greenberger-Horne-Zeilinger) state to date using 120 superconducting qubits. The content focuses on the technical challenges of creating large-scale entanglement, which is highly sensitive to noise and decoherence. Key themes include quantum state preparation, error mitigation techniques, and hardware benchmarking. The significance lies in demonstrating scalable quantum control and advancing quantum computing toward practical applications requiring large entangled states. The paper emphasizes the combination of optimized compilation, error detection, and temporary uncomputation as the key innovations enabling this achievement. Extraction Strategy: The summarization strategy prioritizes the core scientific achievement and methodology while maintaining technical accuracy. The approach focuses on: (1) identifying the primary research contribution (120-qubit GHZ state), (2) extracting the key technical innovations (optimized compilation, error detection), (3) reporting quantitative results (fidelity measurements), (4) contextualizing the significance within quantum computing, and (5) preserving the technical precision of quantum information science terminology. The strategy avoids oversimplification while making the content accessible to readers with basic quantum computing knowledge. Knowledge Mapping: This research sits at the intersection of quantum information science, superconducting quantum hardware, and quantum error correction. It builds upon decades of work on entanglement generation, particularly GHZ states (also known as Schrödinger cat states), which have been fundamental testbeds for quantum mechanics since their theoretical proposal. The work connects to broader efforts in quantum computing scalability, error mitigation, and fault-tolerant quantum computation. It represents progress toward practical quantum advantage by demonstrating control over increasingly large quantum systems, with implications for quantum simulation, quantum metrology, and future quantum algorithms requiring massive entanglement.