Heterogenous QEC codes boost efficiency in Quantinuum’s Helix architecture

Quantinuum has experimentally validated its Helix quantum error correction architecture on the Helios system, achieving record fidelity in quantum operations, the company says. The system demonstrates “logical memory, logical computation, and logical entanglement”, moving beyond results limited to physical qubits and eliminating the need for post-selection techniques. Helix optimizes for both “magic” and “gates” using a heterogenous code approach, minimizing the physical qubit and time overhead required for fault-tolerant computation. “With this demonstration, we have put all the pieces together,” said a Quantinuum representative, pointing to a foundation for scalable, fault-tolerant quantum computing. Quantinuum’s Helix Architecture for Scalable Quantum Computing Minimized spacetime volume, achieved through exotic entanglement schemes and impossible without reconfigurable qubit connectivity, defines the core capability of Quantinuum’s Helix architecture. Unlike traditional quantum error correction codes relying on simple, two-dimensional entanglement networks, Helix utilizes more complex configurations, comparable to a cat’s cradle, to reduce the resources needed for fault-tolerant computation. This design choice directly addresses a key limitation of earlier processors, enabling a reduction in the number of physical qubits required per logical qubit while maintaining computational speed. The Helix code itself is constructed by concatenating a [ ] code with a [ ] code, a specific combination designed to optimize performance characteristics. The ability to preserve encoded quantum information at a lower error rate than the underlying physical operations is central to the Helix architecture’s success, and has now been experimentally validated without relying on post-selection techniques. As Quantinuum frames its development roadmap, it relies on this ability to combine efficient logical gates with multiple QEC encodings, according to the company. The validation of Helix on the Helios system represents a critical step toward realizing practical, scalable fault-tolerant quantum computing, according to the company. The architecture’s design allows for logical computation without requiring a corresponding increase in the number of encoded logical qubits, a significant advantage for complex algorithms.

The team expects the same code to be even more performant when implemented on the forthcoming Apollo system, building on the current results achieved with Helios. Quantinuum highlights that this demonstration is a harmonious whole encompassing a candidate architectural code, logical computation capabilities, multiple encodings within a single architecture, and compatibility with commercial hardware. The company believes this validation of a fault-tolerant architecture on real hardware signifies a substantial move toward quantum computers capable of tackling meaningful problems at scale, marking a transition away from the limitations of the Noisy Intermediate-Scale Quantum (NISQ) era, the firm reports. The low logical error rates observed, coupled with practical logical operations, validate the company’s roadmap and suggest a clear path towards building increasingly powerful and reliable quantum systems.

Heterogenous Helix Code Minimizes Spacetime Volume with Reconfigurable Connectivity Quantinuum researchers engineered this efficiency by employing reconfigurable connectivity, allowing for entanglement schemes beyond those possible with standard quantum processors. While effective for Clifford gates, fundamental operations in many quantum algorithms, the Helix code is less suited for preparing the necessary states for universal quantum computation. Rather than modify the core code to handle both tasks, the team implemented a heterogenous architecture, utilizing a second code optimized specifically for magic state preparation, Quantinuum reports. This division of labor, employing different codes for different computational needs, significantly improves overall efficiency and reduces the total qubit count required. To demonstrate this capability, researchers prepared a three-logical-qubit GHZ state spanning both the surface code and the Helix code, creating a truly heterogenous quantum structure. Chain-mapped gates were used to link these disparate encodings, resulting in a logical GHZ state with a fidelity of 99.925% and an upper bound of 99.975%.

Helios Demonstrates Record-Breaking Logical Memory with Leakage Reduction Achieving a 99% fidelity in a single layer of entanglement, Quantinuum’s Helios system demonstrated high-performance quantum computation with its trapped-ion technology. A 99.925% lower bound fidelity for a logical GHZ state demonstrates a quantifiable improvement in the stability of multi-qubit entanglement within the Helix architecture.

The team linked disparate encodings using chain-mapped gates to create a three-qubit GHZ state, an important step toward more complex quantum computations. The demonstration extends beyond simply achieving logical operations; the team successfully preserved encoded quantum information for extended periods, mitigating a primary source of error on the Helios platform, leakage, the company’s account states. Through 20 rounds of syndrome extraction, they recorded a per-qubit, per-round error rate of 4.6 x 10 -5, without relying on post-selection techniques. Further refinement, employing a modest 0.5% post-selection, reduced the block logical error per round to 1.9 x 10 -5, highlighting the potential for even greater fidelity with minimal data loss. Quantum memory performance remains a fundamental building block for advancing fault-tolerant quantum computing. Beyond memory, the Helix architecture also delivered a logical error rate, a quantifiable improvement over the physical two-qubit Clifford error rate on Helios, again achieved without post-selection. This efficiency gain is partially attributable to the team’s adaptive syndrome extraction technique, which reduces the number of physical gates required for each logical gate, Quantinuum claims. This reduction in gate count also shortens the physical runtime. The ability to utilize multiple QEC encodings within a single fault-tolerant architecture is a key architectural advantage, enabling improved efficiency and reduced qubit requirements. This reconfigurable connectivity allows the system to dynamically adapt to the demands of different quantum algorithms and error profiles. Importantly, these results were not obtained on a specialized testbed or limited-functionality hardware; the experiments were conducted on the same Helios system currently available to Quantinuum’s customers for their research. Simulations suggest that anticipated improvements in physical fidelity with the upcoming Apollo system will further align logical error rates with the company’s long-term roadmap targets.

The team’s success in mitigating leakage through circuit-level reduction units and new leakage repump capacity further underscores the practical viability of the Helix architecture. Automorphism & Transversal Gates Enable Efficient Logical Computation The Helix architecture uses a specific set of gate types to accelerate logical computation, minimizing the demands on physical hardware. Transversal gates and automorphisms, gates accomplished through software-level qubit relabeling, allow for operations that bypass complex physical interactions, streamlining the process and reducing overhead. These techniques enable logical circuits to run with fewer physical resources and in less time than many alternative approaches, a critical advantage as quantum systems scale. The efficiency gains stem from the code’s design, which prioritizes these simpler gate implementations. Performing gates across logical qubits can be challenging because they are built from entangled physical qubits, sometimes even sharing individual physical qubits between multiple logical qubits; however, Helix minimizes this complexity.

The team demonstrated that a substantial portion of logical circuits can be executed using only physical single-qubit gates and qubit relabeling, effectively realizing some operations “for free” through ion transport and software adjustments. This approach drastically reduces both the number of qubits needed for encoding and the overall circuit complexity, lessening the demands on physical resources and shortening runtime. Experimentally, researchers benchmarked the complete logical Clifford group, all gates excluding T gates, while interleaving up to 27 rounds of syndrome extraction to validate the code’s computational abilities. Both gate operations and qubit idling contribute to errors, so reductions in these areas directly translate to lower logical error rates.

The team reports demonstrating an ability to compute while simultaneously showing significant improvement over the physical level without relying on post-selection. This marks the first demonstration of randomized benchmarking on a code encoding more than one logical qubit, a milestone for the field. The architecture’s design also addresses the need for non-Clifford operations, essential for universal fault-tolerant computation. While Clifford gates alone are insufficient, the Helix code provides access to the necessary “magic” resource states, enabling a complete toolkit for quantum algorithms. By construction, the code offers a variety of logical gates implementable with minimal physical overhead, a feature that distinguishes it from many other quantum error correction schemes. The use of heterogenous quantum error correction codes within Helix further optimizes performance, balancing the demands of “magic” and gate operations. The foundation laid by Helix is intended to support the upcoming Apollo system, suggesting a clear path toward increasingly powerful and reliable quantum computers.

The team’s success in implementing these efficient gate types and demonstrating logical computation represents a step toward realizing the full potential of fault-tolerant quantum computing, moving beyond isolated results and toward a functional, scalable architecture. Source: https://www.quantinuum.com/blog/helix-a-new-architecture-for-enterprise-scale-fault-tolerant-quantum-computing More like thisQuantum Research NewsShuttling electrons like on a conveyor belt boosts qubit performanceQuantum Error CorrectionChalmers speeds quantum operations 1,000x, nearing fault toleranceQuantum Computing Business NewsQubic lands $1.5M Canadian deal for quantum amplifiersQuantum Research NewsDynamical Decoupling Shields Qubits From Heavy-Hex CrosstalkStay currentSee today’s quantum computing news on Quantum Zeitgeist for the latest breakthroughs in qubits, hardware, algorithms, and industry deals. Tags: