Anette Messinger, Valentin Torggler, Berend Klaver, Michael Fellner, Wolfgang Lechner (Apr 18 2024).
Abstract: We present a fault-tolerant universal quantum computing architecture based on a code concatenation of noise-biased qubits and the parity architecture. The parity architecture can be understood as a LDPC code tailored specifically to obtain any desired logical connectivity from nearest neighbor physical interactions. The code layout can be dynamically adjusted to algorithmic requirements on-the-fly. This allows reaching arbitrary code distances and thereby exponential suppression of errors with a universal set of fault-tolerant gates. In addition to the previously explored tool-sets for concatenated cat codes, our approach features parallelizable interactions between arbitrary sets of qubits by directly addressing the parity qubits in the code. The proposed scheme enables codes with less physical qubit overhead compared to the repetition code with the same code distances, while requiring only weight-3 and weight-4 stabilizers and nearest neighbor 2D square-lattice connectivity.