Architecture for fast implementation of qLDPC codes with optimized Rydberg gates

Architecture for fast implementation of qLDPC codes with optimized Rydberg gates

April 30, 2024 | C. Poole, T. M. Graham, M. A. Perlin, M. Otten, and M. Saffman
This paper presents an architecture for the fast implementation of bivariate bicycle codes (qLDPC codes) using optimized Rydberg gates between stationary neutral atom qubits. The proposed architecture reduces the maximum Euclidean communication distance required for non-local parity check operators, enabling a quantum error correction cycle time of approximately 1.2 ms for a [[144, 12, 12]] code, an order of magnitude faster than previous designs. The key innovations include an optimized qubit layout that reduces the maximum communication distance by nearly a factor of three and an optimized Rydberg gate design that minimizes the required two-atom interaction strength while maintaining high fidelity and fast speed. These improvements allow for the implementation of high-performance bicycle codes up to distance d = 18 without relying on atom transport. The bivariate bicycle codes have encoding rates exceeding those of the surface code, competitive pseudothresholds, and a Tanner graph with "thickness" 2. The need for long-distance interactions is intrinsic to codes that improve on the density of stored quantum information compared to the surface code. Previous implementations of these codes using neutral atom qubits with atom transport techniques resulted in slow QEC cycle times, which is a limitation for applications requiring deep circuits or large numbers of samples. The proposed architecture uses fast optical beam scanning to reduce the QEC cycle time by more than an order of magnitude compared to transport-based approaches. The optimized layout reduces the maximum communication distance required for parity check operations, while the optimized Rydberg gate design enables CZ entangling operations with fidelity F > 0.999 at distances greater than 12 μm. The estimated QEC cycle time for the [[144, 12, 12]] code is 1.2 ms, which is significantly faster than existing proposals. The paper also discusses the design of Rydberg gates, including the use of analytical pulse shapes that improve gate fidelity. The fidelity of a Rydberg-mediated CZ gate is fundamentally limited by the interaction strength and Rydberg state lifetime. The proposed analytical pulse shape achieves a fidelity of F = 0.9989 with a single pulse, demonstrating the potential for high-fidelity gates at long distances. The paper also addresses the challenge of achieving fast qubit measurements, which is critical for the performance of the QEC cycle. The results show that the proposed architecture can achieve fast QEC cycles with high fidelity, making it a promising approach for implementing qLDPC codes in neutral atom quantum systems.This paper presents an architecture for the fast implementation of bivariate bicycle codes (qLDPC codes) using optimized Rydberg gates between stationary neutral atom qubits. The proposed architecture reduces the maximum Euclidean communication distance required for non-local parity check operators, enabling a quantum error correction cycle time of approximately 1.2 ms for a [[144, 12, 12]] code, an order of magnitude faster than previous designs. The key innovations include an optimized qubit layout that reduces the maximum communication distance by nearly a factor of three and an optimized Rydberg gate design that minimizes the required two-atom interaction strength while maintaining high fidelity and fast speed. These improvements allow for the implementation of high-performance bicycle codes up to distance d = 18 without relying on atom transport. The bivariate bicycle codes have encoding rates exceeding those of the surface code, competitive pseudothresholds, and a Tanner graph with "thickness" 2. The need for long-distance interactions is intrinsic to codes that improve on the density of stored quantum information compared to the surface code. Previous implementations of these codes using neutral atom qubits with atom transport techniques resulted in slow QEC cycle times, which is a limitation for applications requiring deep circuits or large numbers of samples. The proposed architecture uses fast optical beam scanning to reduce the QEC cycle time by more than an order of magnitude compared to transport-based approaches. The optimized layout reduces the maximum communication distance required for parity check operations, while the optimized Rydberg gate design enables CZ entangling operations with fidelity F > 0.999 at distances greater than 12 μm. The estimated QEC cycle time for the [[144, 12, 12]] code is 1.2 ms, which is significantly faster than existing proposals. The paper also discusses the design of Rydberg gates, including the use of analytical pulse shapes that improve gate fidelity. The fidelity of a Rydberg-mediated CZ gate is fundamentally limited by the interaction strength and Rydberg state lifetime. The proposed analytical pulse shape achieves a fidelity of F = 0.9989 with a single pulse, demonstrating the potential for high-fidelity gates at long distances. The paper also addresses the challenge of achieving fast qubit measurements, which is critical for the performance of the QEC cycle. The results show that the proposed architecture can achieve fast QEC cycles with high fidelity, making it a promising approach for implementing qLDPC codes in neutral atom quantum systems.
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