68q/error-correction•u/Rihaan Shah• 7 months ago PinnedResearchThreshold Theorems for the Surface Code under Non-Markovian NoiseStandard fault-tolerance proofs often assume Markovian noise (independent per time step). However, in many superconducting platforms, 1/f noise and cosmic ray events introduce significant temporal and spatial correlations. Numerical Analysis: We've been simulating the surface code under a correlated noise model where error rates $p(t)$ are coupled across multiple cycles. We observe a significant shift in the threshold from ~1% down to ~0.4% depending on the correlation length $\xi$. Theoretical Questions: - Can **Decoupling Sequences** effectively 'Markovianize' the noise before the syndrome extraction? - How do **3D Gauge Color Codes** handle these correlations compared to the standard Toric code? Check out this code snippet for a basic depolarizing noise sim under correlation: ```python def correlated_noise(qubits, p, correlation_factor): # Simplified simulation of spatially correlated errors for i in range(len(qubits)): if random.random() 5 CommentsShareReport
131q/error-correction•u/Alice JohnsonMENTOR• 7 months ago PinnedRESEARCHImplementing Surface Codes on IBM Brussels: A New PerspectiveSurface codes are currently the most promising candidate for fault-tolerant quantum computing due to their high error threshold. Recently, I've been experimenting with the $d=3$ surface code. The logical qubit is encoded in a grid of physical qubits where the stabilizers are: $$Z_p = \prod_{i \in p} Z_i, \quad X_p = \prod_{i \in p} X_i$$ We're seeing a significant improvement in logical error rates as we scale, but the decoders (matching algorithms) are still a bottleneck. What's everyone's favorite MWPM implementation?8 CommentsShareReport
124q/error-correction•u/Alice JohnsonMENTOR• 7 months agoTECHNICALLDPC Codes vs Surface Codes for 2D ArchitecturesTanner graphs and belief propagation are standard for LDPC. Can we map these effectively to a 2D grid without needing an insane number of SWAPs?5 CommentsShareReport
174q/error-correction•u/Rihaan Shah• 7 months agoRESEARCHImplementing Surface Codes: A New PerspectiveSurface codes rely on stabilizer measurements to identify errors. I've been looking at d=5 grids. The decoding overhead is still the biggest challenge.5 CommentsShareReport