Sūtra
Under research

Quantum information, held together.

A useful quantum computer is mostly error correction. Sutra hunts for the codes that do it better — and a reproducible search found ones that beat IBM's Gross code on the field's figure of merit, one of them certified by an exact solver. The same engine takes aim at quantum computing's other unsolved, billion-dollar problems.

1.8–4.4×
better than Gross on k·d²/n
2.00×
exact-certified (MIP solver)
60,000
codes searched, fully reproducible
Stabiliser neighbourhood · 12×8 torus
weight 8max L1 = 4 · heavy-hex ✓
L qubit (via A)R qubit (via B)X-check torus wrap

The certified result — [[192,8,24]], distance proven exactly. A real bivariate-bicycle code on its torus, drawn from the published polynomials.

The exchange rate of fault tolerance
k · d2 / n

Logical qubits k, distance d, physical qubits n. It rewards encoding more logical qubits and tolerating more errors, while penalising qubit overhead — the single number that captures whether a code is a good deal.

Gross 12Sutra codes 22 – 53
The idea

A useful quantum computer is mostly error correction. Make the codes better and you make the whole machine cheaper.

Every logical qubit you can actually compute with is built from hundreds or thousands of noisy physical qubits, held together by a quantum error-correcting code. The code's quality is the exchange rate between the two — and it dominates the cost of fault-tolerant quantum computing. Sutra treats finding better codes as a search problem: we built a validated evaluator, swept 60,000 candidates under a real hardware-connectivity constraint, and found bivariate-bicycle codes that beat IBM's Gross code on the standard figure of merit, k·d²/n — one of them certified by an exact solver. The same machinery points at the field's other open problems in fault tolerance.

01

The exchange rate

Logical qubits (k), error tolerance (distance d), physical-qubit cost (n). k·d²/n is the field-standard single number for whether a code is a good deal. IBM's Gross [[144,12,12]] code scores 12. Our codes score 22–53 — 1.8× to 4.4× better — under a heavy-hex connectivity constraint Gross does not satisfy.

02

Discovery by search

Bivariate-bicycle codes are defined by two polynomials over a torus. We search that space — random at scale, then evolutionary — scoring each candidate with an evaluator first validated to reproduce all five of IBM's published BB codes exactly. 14 of the top 50 beat Gross after rigorous re-checking.

03

Certified, not just claimed

Fast decoders give an upper bound on a code's distance; they can over-state it. For our lead code we ran an exact MIP solver over every logical coset — and it corrected the estimate from 26 down to 24. We label every distance as exact or bounded, and we publish a code that failed verification to make the point.

04

Honest about hardware

A higher k·d²/n buys you less margin elsewhere: our highest-scoring codes currently have a circuit-level threshold below today's IBM gate-error rates, and the hardware demo is designed but not yet run. We report that as the central result, not a footnote — it is what the next phase is for.

What the search found

Verified, certified, and honest.

All findings
01 · Certified
2.00×

[[192,8,24]], distance proven exactly by a MIP solver — every coset solved. The solver even corrected the fast-decoder estimate from 26 down to 24.

02 · Frontier
4.41×

[[196,18,24]] — the highest figure of merit found, and just 10.9 physical qubits per logical vs Gross's 12. Distance is a rigorous upper bound, not yet exact.

03 · The tradeoff
↓ p_th

The honest part: the highest-scoring codes currently have a circuit-level threshold below today's hardware. The tradeoff is the finding — and the next phase's target.

Beyond the first front

Error correction is the first front, not the only one.

The same search-and-certify machinery generalises. These are the adjacent open problems we are built to attack — scoped honestly as the venture's expanding frontier, not as solved work.

01

Fault-tolerant decoders & schedules

Real-time, hardware-aware decoding and hook-error-avoiding syndrome schedules — what turns a good code into a usable one.

02

Certified code distance

Exact distance via MIP/SAT, generalised so that a code's protection is proven, not merely estimated by a fast decoder.

03

Biased-noise tailoring

Codes with asymmetric distance (d_X ≠ d_Z) matched to a chip's real, biased noise — squeezing more protection from the same qubits.

04

Hardware-native embedding

Codes designed to sit on a specific processor's connectivity graph from the start, not retrofitted — cutting routing overhead.

05

Logical-gate layout

Magic-state and lattice-surgery layouts on high-rate qLDPC codes — the path from quantum memory to quantum computation.

06

Beyond bivariate bicycle

Generalised and multivariate qLDPC families, searched with the same validated, reproducible pipeline.

Intellectual honesty

Proven, bounded, or pending.

In quantum error correction the gap between a claimed distance and a certified one is where careers go to die. So we keep a ledger, and label every line exactly.

Proven
Codes beating Gross on k·d²/n
14 of the top 50 candidates beat Gross after rigorous BP+OSD re-verification; reproducible from the open release.
Certified
[[192,8,24]] distance d = 24
Exact MIP solver, every one of 255 cosets solved. It corrected the fast-decoder estimate downward — the value of certification.
Bounded
High-k distances (e.g. [[196,18,24]], [[192,16,20]])
BP+OSD upper bounds at partial coverage (≈12–40% of logical classes). Strong, but not yet exactly certified — k is too large for the MIP solver.
Bounded
Heavy-hex implementability
Enforced via a toroidal L1 ≤ 4 locality surrogate; an explicit Eagle/Heron graph embedding has not yet been produced.
Pending
Circuit-level threshold vs Gross
Currently below IBM gate-error rates — the figure-of-merit gain trades against threshold. Full-scale threshold runs and a fault-tolerant schedule are the next phase.
Pending
Novelty vs the literature
Smith-Normal-Form analysis rules out equivalence to IBM's published codes; a live arXiv / code-tables dedupe is still required before any novelty claim is final.
Null result
LLM-guided discovery
Tested honestly across three rounds: language models are good constraint-respecting proposers but did not beat random search at finding frontier codes. Reported as a negative result.
Not yet
Hardware demonstration
An IBM memory-experiment protocol is designed and preflighted, but has not been run. No experimental logical-error claim is made.
The bet

Drive down the cost of a logical qubit — and keep driving.

Quantum computing's bottleneck is not the number of physical qubits; it is how many of them each logical qubit costs. That overhead is set by the error-correcting code, the decoder, and how well both fit the hardware. Sutra's bet is that this whole stack is searchable and co-designable — that better codes, better decoders, and hardware-tailored fault tolerance can be discovered systematically rather than hand-crafted one paper at a time. We start where we already have a verified, reproducible result — better codes — and extend outward into the adjacent million-dollar problems of fault tolerance.

Back the research

This is the stage where backing matters most — before the revenue, while the result is hardened from “strong and reproducible” into “undeniable.” The decisive next steps are verification compute and a hardware demo.

See how to support

Sponsorship & partnership — not equity. There is no product yet, and we won't pretend otherwise.

सूत्र · the thread that holds

Don't take our word. Inspect the codes.

Every code, its lattice, its figure of merit, and exactly how its distance was verified — open and reproducible.