Topological Dynamical Decoupling Achieves Complete Pulse Error Cancellation with Robustness to Detuning

Systematic pulse errors currently limit the precision of quantum control, hindering the development of reliable quantum technologies. Nayden P. Nedev and Nikolay V. Vitanov, from the Center for Quantum Technologies at Sofia University, now present a new approach to overcoming this challenge, introducing a family of dynamical decoupling sequences that completely cancel pulse area errors. This method achieves exact error cancellation without the need for complex numerical optimisation, offering a robust and analytically solvable solution for any sequence length, and importantly, demonstrating resilience to variations in system parameters. The team validates these sequences on superconducting qubits from both IBM and IQM processors, observing results that closely match theoretical predictions, and establishing a new, hardware-efficient pathway towards suppressing errors in a wide range of quantum computing, sensing, and memory applications.

Dynamical decoupling is a cornerstone technique for mitigating decoherence in quantum systems. This research focuses on constructing sequences, termed Tn, that satisfy a specific topological phase condition. Unlike some conventional composite sequences, Tn requires no numerical optimization and admits closed-form analytic phases for arbitrary sequence length, while also providing substantial robustness to detuning. Researchers demonstrate these sequences on superconducting transmon qubits from both IBM Quantum processor ibm_torino and IQM Quantum processor Garnet, observing population plateaus in close agreement with theoretical predictions. These results establish a new paradigm for hardware-efficient error suppression, broadly applicable across quantum computing, sensing, and memory platforms.

Tn Sequences Cancel Systematic Pulse Errors

This research introduces a new family of dynamical decoupling sequences, called Tn, designed to exactly cancel systematic pulse area errors to all orders. The team achieved this by carefully controlling the phases of the pulses within the sequence, a technique termed topological dynamical decoupling due to the mathematical properties governing these phases. A key innovation is that the Tn sequences are analytically defined, meaning a formula generates them for any desired complexity, a significant advantage over techniques relying on complex numerical calculations. The researchers developed a mathematical framework for constructing the Tn sequences, outlining the conditions necessary for perfect cancellation of systematic errors.

They then implemented these sequences on two distinct superconducting transmon qubit platforms: IBM Quantum’s ibm_torino and IQM Quantum’s Garnet. Through careful calibration of control pulses and precise measurement of qubit responses under various noise conditions, they validated the theoretical predictions. The performance of Tn sequences was benchmarked against commonly used dynamical decoupling sequences like CPMG and URn, demonstrating superior performance, with URn showing comparable results due to its inherent properties. Experiments confirmed that the Tn sequences effectively suppress systematic pulse area errors as predicted by the theory.

The sequences outperformed most benchmarked techniques, demonstrating improved robustness to noise and imperfections. Importantly, the error compensation provided by Tn sequences is independent of the initial qubit state, making them versatile for diverse quantum algorithms. Furthermore, the sequences maintain performance even with slight variations in qubit frequency, demonstrating robustness to detuning. The experiments revealed clear plateau regions in the qubit’s response, indicating effective error suppression across a wide range of noise conditions. This research offers a pathway to hardware-efficient quantum control, improving performance without requiring significant hardware improvements. The sequences can extend qubit coherence times, making them suitable for quantum memories, and enhance the sensitivity of quantum sensors. They can also be integrated into more complex error mitigation and correction frameworks, contributing to the development of scalable quantum computers by reducing the need for precise hardware calibration.

Topological Control Cancels Quantum Pulse Errors

Scientists have achieved exact cancellation of pulse area errors in quantum systems using a new family of dynamical decoupling sequences, denoted Tn. These sequences enforce a simple topological phase condition, delivering infinite order suppression of systematic pulse errors, while simultaneously demonstrating substantial robustness to detuning. The research establishes a new paradigm for hardware-efficient error suppression applicable across computing, sensing, and memory platforms. The team derived Tn sequences from a criterion imposed on the control phases, enabling complete error cancellation independent of microscopic details.

Experiments using superconducting transmon qubits on both IBM’s ibm_torino and IQM’s Garnet processors confirmed the theoretical predictions, observing population plateaus in close agreement with calculations. Specifically, the sequences achieve exact cancellation by satisfying two conditions: neighboring control phases must differ by an integer multiple of pi, and the sum of complex exponential terms associated with these phases must equal zero. The researchers demonstrated the versatility of Tn sequences, generating phase sets for sequences up to length 24. For example, a T2 sequence utilizes phases of 0 and 1π, while a T4 sequence employs 0, 0, 1, and 1π. Higher-order sequences exhibit increasingly complex phase arrangements, but maintain the core principle of error cancellation through topological constraints. These results demonstrate a significant advancement in quantum control, offering a pathway to more reliable and scalable quantum technologies.

Topological Decoupling Cancels Qubit Pulse Errors

This research presents a new family of dynamical decoupling sequences, denoted Tn, which effectively suppress errors in quantum systems. These sequences achieve complete cancellation of pulse area errors, a significant source of inaccuracy in controlling qubits, by enforcing a specific topological phase condition. Unlike existing methods that often require complex numerical optimization, the Tn sequences possess a closed-form analytic solution, meaning their parameters can be calculated directly for any sequence length, and demonstrate robustness even with slight variations in system tuning. Demonstrations on both IBM and IQM superconducting qubits confirm the theoretical predictions, with experimental results closely matching predicted population plateaus, indicating successful error suppression.

This achievement establishes a new approach to hardware-efficient error mitigation, with potential applications extending to quantum computing, sensing, and the development of quantum memories. While acknowledging that the sequences were tested on specific qubit platforms, the authors suggest future work will explore integration with existing error correction frameworks and investigate the potential for further optimization. They also highlight the importance of pulse-level control, as demonstrated by IQM’s technology, for maximizing the benefits of these sequences and achieving improved quantum system performance.