|
| 1 | +####################################################### |
| 2 | +## This is a code entry in the error correction zoo. ## |
| 3 | +## https://github.com/errorcorrectionzoo ## |
| 4 | +####################################################### |
| 5 | + |
| 6 | +code_id: stab_20_2_6 |
| 7 | +physical: qubits |
| 8 | +logical: qubits |
| 9 | + |
| 10 | +name: '\([[20,2,6]]\) B\&C phantom code' |
| 11 | +short_name: '\([[20,2,6]]\)' |
| 12 | +introduced: '\cite{arxiv:2601.20927,arxiv:2605.15344}' |
| 13 | + |
| 14 | +description: | |
| 15 | + Self-dual CSS code on 20 physical qubits encoding two logical qubits with distance 6. |
| 16 | + The code is obtained by binarizing the \([[5,1,3]]_4\) code in the self-dual normal basis \(\{\omega,\omega^2\}\) to the \([[10,2,3]]\) binarized Galois-qudit code and then concatenating each qubit pair with the \([[4,2,2]]\) code \cite{arxiv:2601.20927}. |
| 17 | +
|
| 18 | + Physical qubits are arranged in five blocks of four, where block \(j\) corresponds to the \(j\)-th \(\mathbb{F}_4\) qudit of the \([[5,1,3]]_4\) code. |
| 19 | + Stabilizer generators of the \([[4,2,2]]\) inner code on each block are \(ZZZZ\) and \(XXXX\); the outer stabilizers are the lifted images of the eight stabilizer generators of the \([[10,2,3]]\) code using the logical-operator map |
| 20 | + \(X^\omega\mapsto XXII\), \(X^{\omega^2}\mapsto XIXI\), \(Z^\omega\mapsto IZIZ\), \(Z^{\omega^2}\mapsto IIZZ\) within each block. |
| 21 | +
|
| 22 | + A stabilizer tableau for the code is \cite{arxiv:2601.20927} |
| 23 | + \begin{align} |
| 24 | + \begin{smallmatrix} |
| 25 | + Z & Z & Z & Z & I & I & I & I & I & I & I & I & I & I & I & I & I & I & I & I \\ |
| 26 | + I & I & I & I & Z & Z & Z & Z & I & I & I & I & I & I & I & I & I & I & I & I \\ |
| 27 | + I & I & I & I & I & I & I & I & Z & Z & Z & Z & I & I & I & I & I & I & I & I \\ |
| 28 | + I & I & I & I & I & I & I & I & I & I & I & I & Z & Z & Z & Z & I & I & I & I \\ |
| 29 | + I & I & I & I & I & I & I & I & I & I & I & I & I & I & I & I & Z & Z & Z & Z \\ |
| 30 | + I & Z & I & Z & I & Z & I & Z & I & Z & I & Z & I & Z & I & Z & I & I & I & I \\ |
| 31 | + I & I & Z & Z & I & I & Z & Z & I & I & Z & Z & I & I & Z & Z & I & I & I & I \\ |
| 32 | + I & I & I & I & I & Z & I & Z & I & Z & Z & I & I & I & Z & Z & I & Z & I & Z \\ |
| 33 | + I & I & I & I & I & I & Z & Z & I & Z & I & Z & I & Z & Z & I & I & I & Z & Z \\ |
| 34 | + X & X & X & X & I & I & I & I & I & I & I & I & I & I & I & I & I & I & I & I \\ |
| 35 | + I & I & I & I & X & X & X & X & I & I & I & I & I & I & I & I & I & I & I & I \\ |
| 36 | + I & I & I & I & I & I & I & I & X & X & X & X & I & I & I & I & I & I & I & I \\ |
| 37 | + I & I & I & I & I & I & I & I & I & I & I & I & X & X & X & X & I & I & I & I \\ |
| 38 | + I & I & I & I & I & I & I & I & I & I & I & I & I & I & I & I & X & X & X & X \\ |
| 39 | + X & X & I & I & X & X & I & I & X & X & I & I & X & X & I & I & I & I & I & I \\ |
| 40 | + X & I & X & I & X & I & X & I & X & I & X & I & X & I & X & I & I & I & I & I \\ |
| 41 | + I & I & I & I & X & X & I & I & X & I & X & I & I & X & X & I & X & X & I & I \\ |
| 42 | + I & I & I & I & X & I & X & I & I & X & X & I & X & X & I & I & X & I & X & I |
| 43 | + \end{smallmatrix}~. |
| 44 | + \end{align} |
| 45 | + Rows 1--5 are the \(Z\)-type inner stabilizers of each \([[4,2,2]]\) block; rows 6--9 are the lifted outer \(Z\)-type stabilizers; rows 10--14 are the \(X\)-type inner stabilizers; rows 15--18 are the lifted outer \(X\)-type stabilizers. |
| 46 | +
|
| 47 | +protection: | |
| 48 | + Detects errors on up to 5 qubits and corrects errors on up to 2 qubits. |
| 49 | +
|
| 50 | +features: |
| 51 | + transversal_gates: |
| 52 | + - 'Logical CNOT gates in both directions between the two logical qubits are realized by qubit permutations within a code block \cite{arxiv:2601.20927,arxiv:2605.15344}.' |
| 53 | + - 'Fold-diagonal logical \(SS\) gates are available from the self-duality of the outer \([[5,1,3]]_4\) code and the inner \([[4,2,2]]\) layer \cite{arxiv:2601.20927}.' |
| 54 | + |
| 55 | + fault_tolerance: |
| 56 | + - 'Selective state filtering (post-selection): logical error rates of \(\approx 2\times 10^{-6}\) per round of Steane-style error correction at physical error rate \(p=10^{-3}\), without being fully fault-tolerant \cite{arxiv:2605.15344}.' |
| 57 | + |
| 58 | +relations: |
| 59 | + parents: |
| 60 | + - code_id: bc_phantom |
| 61 | + detail: 'The \([[20,2,6]]\) code is the B\&C phantom code obtained from the \([[5,1,3]]_4\) Galois-qudit CSS code \cite{arxiv:2601.20927,arxiv:2605.15344}.' |
| 62 | + - code_id: self_dual_css |
| 63 | + detail: 'The \([[20,2,6]]\) code is a self-dual CSS code obtained from the \([[5,1,3]]\) code via the BLT mapping and concatenation with \([[4,2,2]]\) \cite[Corr. 2]{arxiv:2605.15344}\cite[Corr. 1]{arxiv:1004.3791}.' |
| 64 | + cousins: |
| 65 | + - code_id: stab_5_1_3 |
| 66 | + detail: 'The \([[20,2,6]]\) code is obtained from the \([[5,1,3]]\) five-qubit code via the BLT mapping (Lemma 1) and concatenation with the \([[4,2,2]]\) code (Corollary 2) \cite{arxiv:2605.15344}\cite[Corr. 1]{arxiv:1004.3791}.' |
| 67 | + - code_id: stab_4_2_2 |
| 68 | + detail: 'The \([[20,2,6]]\) code is obtained by concatenating each qubit pair of the \([[10,2,3]]\) binarized code with the \([[4,2,2]]\) code \cite{arxiv:2601.20927,arxiv:2605.15344}.' |
| 69 | + - code_id: stab_10_2_3 |
| 70 | + detail: 'The \([[20,2,6]]\) code is obtained by concatenating each qubit pair of the \([[10,2,3]]\) binarized Galois-qudit code with the \([[4,2,2]]\) code \cite{arxiv:2601.20927}.' |
| 71 | + |
| 72 | + |
| 73 | +# Begin Entry Meta Information |
| 74 | +_meta: |
| 75 | + changelog: |
| 76 | + - user_id: VictorVAlbert |
| 77 | + date: '2026-05-22' |
0 commit comments