Bivariate bicycle (BB) code[1] 

Description

One of several Abelian 2BGA codes which admit time-optimal syndrome measurement circuits that can be implemented in a two-layer architecture, a generalization of the square-lattice architecture optimal for the surface codes.

The qubit connectivity graph is not quite a 2D grid and is instead decomposable into two planar subgraphs of degree three; there exists an optimized layout minimizing Euclidean communication distance for check operators [2]. There are \(n\) \(X\) and \(Z\) check operators, with each one of weight six.

Several variants and generalizations exist [3,4].

Protection

Admits an \(0.8\%\) pseudo-threshold for circuit-level noise under BP-OSD decoder [1] (cf. [5]).

Rate

When ancilla qubit overhead is included, the encoding rate surpasses that of the surface code. A general \([[n,k,d]]\) bivariate bicycle code requires \(n\) ancilla qubits for encoding, meaning that its ancilla-added encoding rate is \(k/2n\).

Transversal Gates

Logical Pauli operators and fold-transversal gates studied in Ref. [6].

Decoding

Syndrome extraction circuit requires seven layers of CNOT gates regardless of code length. BP-OSD decoder [7] has been extended [1] to account for measurement errors (i.e., the circuit-based noise model [5]).Random and optimized syndrome extraction schedules from Ref. [1] are not distance-preserving.Some long-range check operators can be measured less frequently than others [8].Syndrome extraction circuits called morphing circuits [9], generalizing circuits for the color code [10].

Fault Tolerance

Fault-tolerant state initialization using lattice surgery techniques [11,12] and an ancillary surface code [1].

Parents

Child

Cousin

  • Kitaev surface code — Bivariate bicycle codes are on par with the surface code in terms of threshold, but admit a much higher ancilla-added encoding rate at the expense of having non-geometrically local weight-six check operators.

References

[1]
S. Bravyi et al., “High-threshold and low-overhead fault-tolerant quantum memory”, Nature 627, 778 (2024) arXiv:2308.07915 DOI
[2]
C. Poole et al., “Architecture for fast implementation of qLDPC codes with optimized Rydberg gates”, (2024) arXiv:2404.18809
[3]
L. Voss et al., “Multivariate Bicycle Codes”, (2024) arXiv:2406.19151
[4]
M. Wang and F. Mueller, “Coprime Bivariate Bicycle Codes and their Properties”, (2024) arXiv:2408.10001
[5]
A. G. Fowler, A. M. Stephens, and P. Groszkowski, “High-threshold universal quantum computation on the surface code”, Physical Review A 80, (2009) arXiv:0803.0272 DOI
[6]
J. N. Eberhardt and V. Steffan, “Logical Operators and Fold-Transversal Gates of Bivariate Bicycle Codes”, (2024) arXiv:2407.03973
[7]
P. Panteleev and G. Kalachev, “Degenerate Quantum LDPC Codes With Good Finite Length Performance”, Quantum 5, 585 (2021) arXiv:1904.02703 DOI
[8]
N. Berthusen et al., “Toward a 2D Local Implementation of Quantum LDPC Codes”, (2024) arXiv:2404.17676
[9]
M. H. Shaw and B. M. Terhal, “Lowering Connectivity Requirements For Bivariate Bicycle Codes Using Morphing Circuits”, (2024) arXiv:2407.16336
[10]
C. Gidney and C. Jones, “New circuits and an open source decoder for the color code”, (2023) arXiv:2312.08813
[11]
L. Z. Cohen et al., “Low-overhead fault-tolerant quantum computing using long-range connectivity”, Science Advances 8, (2022) arXiv:2110.10794 DOI
[12]
Q. Xu et al., “Constant-Overhead Fault-Tolerant Quantum Computation with Reconfigurable Atom Arrays”, (2023) arXiv:2308.08648
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Zoo Code ID: qcga

Cite as:
“Bivariate bicycle (BB) code”, The Error Correction Zoo (V. V. Albert & P. Faist, eds.), 2023. https://errorcorrectionzoo.org/c/qcga
BibTeX:
@incollection{eczoo_qcga, title={Bivariate bicycle (BB) code}, booktitle={The Error Correction Zoo}, year={2023}, editor={Albert, Victor V. and Faist, Philippe}, url={https://errorcorrectionzoo.org/c/qcga} }
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“Bivariate bicycle (BB) code”, The Error Correction Zoo (V. V. Albert & P. Faist, eds.), 2023. https://errorcorrectionzoo.org/c/qcga

Github: https://github.com/errorcorrectionzoo/eczoo_data/edit/main/codes/quantum/qubits/stabilizer/qldpc/homological/balanced_product/lp/qcga.yml.