Technology

Encoding, decoding and post-selection — measured on real hardware.

Nandi Q1 is the stack every figure below came out of, run on rented IBM Heron-class processors as paying customers.

See the ledger
99.94%

logical Bell fidelity — [[4,2,2]] encoded, three bases

31/31

independent encoded pairs certified in one job

5.5×

suppression, distance 3 → 5, one basis

100,000

shots per distance point, decoded offline

[[4,2,2]] encoded pairs on IBM Heron-class hardware. Fidelity 95% CI [0.999112, 0.999608], post-selected at 9.4% (Z) / 6.0% (X) acceptance; suppression measured in one basis. Conditions and job IDs on the ledger.

What it is.

Nandi Q1 is our encoding, readout and decoding stack. Every figure above came out of it, on cloud processors we rent as paying customers. It gives us:

  • Encoded. States are prepared inside a distance-2 error-detecting code, not on bare physical qubits.
  • Three-basis readout. ZZ, XX and YY are measured on separate circuits.
  • Post-selected. Runs failing the detection check are discarded, and the acceptance rate is published beside every number.
  • Frozen before submission. Decode conventions are fixed before a job is sent, so the analysis cannot be tuned to the result.
  • Re-derived offline. Raw per-shot arrays are archived; every figure rebuilds on a laptop without a quantum computer.

Run on Nandi Q1.

Three-basis logical Bell state

A [[4,2,2]] encoded pair read out in ZZ, XX and YY on separate circuits, with its confidence interval and acceptance rate published beside it.

See the ledger entry

Thirty-one encoded pairs in one job

Thirty-one independent encoded pairs — 62 logical qubits — certified in one submission, each above the witness threshold with its own confidence interval.

See the ledger entry

A repetition-memory ladder

100,000 shots per distance, decoded offline with minimum-weight matching: a 5.5× suppression from distance 3 to 5, and the floor where it stops.

See the ledger entry

The connectivity tax

Routed onto degree-3 heavy-hex, a surface code costs 270 two-qubit gates at distance 3 and 2,100 at distance 5. We measured what that does to the logical state — and it is why we are designing our own lattice.

Read the design brief

Every figure re-derives offline

Raw per-shot arrays are archived at submission and every number on this page is rebuilt from them on a laptop, without touching a quantum computer. Decode conventions are frozen before a job is sent, so the analysis cannot be tuned to the result.

Re-run them yourself

Placement that earns its couplers

Blocks are placed on calibration-ranked native couplers, so the compiler adds no routing detours. The same pattern that certified one encoded pair placed the whole fleet across the processor in a single submission.

Read the note

Nandi Q1 resources.

Nandi Q1 · stack spec v1.0 · 23 August 2026.