Logical errors fell below one percent on IBM‘s ibm_phoenix processor, marking a key step forward in quantum error correction; this was achieved through strategies including excluding poorly performing components and employing noise informed decoding. Surface codes at distances of both three and five were routinely produced with these low error rates. Highly accurate operations involving quantum bits, the basic units of quantum information, resulted from using error correction on superconducting components, this involved identifying and excluding less reliable parts alongside advanced decoding strategies.

Surface code configurations at distances of three and five were routinely built, achieving logical errors below one percent. This demonstrates progress towards building more stable quantum computers capable of complex calculations by suppressing errors during processing. Logical error rates below one percent have been achieved on IBM’s ibm_phoenix processor; this represents an advance in building practical quantum computers. This was accomplished by employing strategies including identifying and excluding less reliable components, akin to removing faulty parts from a circuit board, alongside advanced decoding techniques.

The work centres around ‘surface codes’, where multiple physical qubits are used together to represent a single, protected unit of quantum information, much like creating redundant copies of vital data for backup purposes. But can these improvements be scaled further, or will component variability continue to pose a fundamental challenge. Detailed findings on qubit operations and entanglement follow.

Defect exclusion unlocks fault tolerance and high fidelity operations on ibm_phoenix

Halving the logical error rate, from 1.9% to 0.9% in memory tests on IBM’s ibm_phoenix processor, is a key improvement enabling sustained fault tolerance previously unattainable due to component variability. Also achieved were Bell-state fidelities exceeding 93% through lattice surgery, combining two adjacent quantum codes. Alongside successful logical teleportation of states and gates with observed fidelities between 78%-93%. Repeated stabilizer measurements, checks of quantum information, strengthened the findings; they maintained improvements in stability up to an overall error probability approaching approximately 1x 10−7 over a sustained period of 170 measurement rounds.

A fast reset operation on qubits reduced leakage errors and sharply improved performance. Logical teleportation experiments involving three logical qubits yielded encouraging results as well, showing gate and state transfer fidelities ranging from 78% to 93%, though these numbers represent strong progress towards fault tolerance but do not yet reflect scalability beyond small code distances or account for complexities introduced by controlling hundreds of physical qubits required for truly useful quantum computations.

Defect exclusion offers near term gains but limits scalability toward full fault

These experiments demonstrate a proactive approach towards error mitigation, identifying and removing flawed components before they impact calculations, but scaling this ‘defect exclusion’ technique presents an obvious tension; discarding underperforming units becomes increasingly unsustainable as systems grow from hundreds to thousands of qubits. The team acknowledges that hardware-level improvements alone aren’t enough for truly fault-tolerant computation, hinting at the need for combination with advanced software correction strategies. Discarding components will not scale indefinitely as quantum systems expand; it is a stepping stone rather than an ultimate solution.

Sophisticated techniques can yield stable computations even with imperfect hardware, paving the way toward stronger error correction methods needed for practical quantum computers. By proactively excluding unreliable components alongside advanced decoding tailored for known imperfections on IBM’s ibm_phoenix processor, the team achieved high-fidelity operations using entangled quantum bits. Successfully performing logical teleportation, transferring quantum states between distant qubits with fidelities ranging from seventy eight to ninety three percent, confirms the viability of these methods beyond simple calculations.

This research demonstrated high-fidelity operation of logical qubits utilizing 120 superconducting qubits on the ibm\_phoenix processor. These results suggest that combining hardware improvements with advanced software correction can improve stability in quantum computations, as evidenced by continued improvement over 170 measurement rounds.

👉 More information
🗞 Entangled logical qubits on a superconducting quantum processor
✍️ Robin Harper, Xanda C. Kolesnikow, Campbell K. McLauchlan, Georgia M. Nixon and Stephen D. Bartlett (The University of Sydney); Benjamin J. Brown (T. J. Watson Research Center)
🧠 ArXiv: https://arxiv.org/abs/2610.32347

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