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Good quantum locally testable codes

Construct stabilizer quantum locally testable codes with constant rate, linear distance, constant check weight and degree, and constant soundness s>0s>0. For mm checks on nn qubits, require $|\operatorname{syn}(E)|/m\ge s,\min_{F:\operatorname{syn}(F)=0}\ope

Source-reported statusAs of 2026-09-04Source & evidence ↓

Problem statement

Construct stabilizer quantum locally testable codes with constant rate, linear distance, constant check weight and degree, and constant soundness s>0s>0. For mm checks on nn qubits, require ∣syn⁡(E)∣/m≥s min⁡F:syn⁡(F)=0wt⁡(EF)/n|\operatorname{syn}(E)|/m\ge s\,\min_{F:\operatorname{syn}(F)=0}\operatorname{wt}(EF)/n for every Pauli error EE.

Lean 4

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Background

The syndrome counts violated checks. Distance in this soundness inequality is distance to the code space: errors are considered modulo zero-syndrome operators, including logical operators, not just modulo stabilizers. This distinguishes local testability from ordinary error-correction distance.

What is known: Panteleev–Kalachev constructed asymptotically good quantum LDPC codes, with constant rate and linear distance; later quantum Tanner constructions provide another route. Earlier fibre-bundle and balanced-product breakthroughs had different parameters and should not all be credited with the full good-code theorem.

Dinur–Lin–Vidick construct almost-good qLTCs with constant rate, bounded-size checks and inverse-polylogarithmic relative distance and soundness. Thus several parameters are close, but the simultaneous constant-parameter target above remains open. Good qLDPC codes and NLTS do not by themselves establish constant local-test soundness, and quantum PCP should not be identified with this particular stabilizer-code construction problem. Related: A6, A18.

Progress & source assessment

Source catalogue review: 4 September 2026. Improved indicates partial progress, including qualified preprint claims.

References
  1. [1]Panteleev & Kalachev, 'Asymptotically good quantum and locally testable classical LDPC codes', STOC 2022 link
  2. [2]Dinur, Lin & Vidick, 'Almost good quantum locally testable codes' (2024) link

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