Good quantum low-density parity-check codes

Ivan B. Djordjević

Shengmei Zhao, Xiu-Li Zhu, Guo-Jun Sun

With the development of quantum error correction techniques, many counterparts of classical error correction coding techniques have been found in quantum area. As the quantum counterpart of a good error correction code in classical communications, quantum low density parity check code becomes a promising coding technique in quantum error correction area. In this paper, a construction method of quantum low density parity check code (quantum LDPC) based on Projective Geometry is proposed, and the quantum code QLDPC [21,6] is selected as an example to illustrate the whole construction procedures. By numerical simulation, the error correction performance of QLDPC [21,6] is discussed over the bit-flipping channel. It is shown that this method is available and has some advantages.

Shengmei Zhao, Bao-yui Zheng, W. F. Wang

In this paper, a construction method of quantum low density parity check codes (quantum LDPC) which based on classical quasi-cyclic sparse sequence is proposed, and the quantum code QLDPC(3,8)(16,6) and QLDPC(3,8)(64,24) are selected as examples to illustrate this construction method. The performances of this kind quantum LDPC codes are discussed over the bit-flipping channel by numerical simulations. The results show that these quantum codes have good ability to correct error in quantum channel.

Ivan B. Djordjević

Guo Zhang, Yuanye Zhu, Ying Li

We propose a fault-tolerant quantum computation scheme that is broadly applicable to quantum low-density parity-check (qLDPC) codes. The scheme achieves constant qubit overhead and a time overhead of O ( d a + o ( 1 ) ) for any [ [ n , k , d ] ] qLDPC code with constant encoding rate and distance d = Ω ( n 1 / a ) . For good qLDPC codes, the time overhead is minimized and reaches O ( d 1 + o ( 1 ) ) . In contrast, code surgery based on gauging measurement and brute-force branching requires a time overhead of O ( d w 1 + o ( 1 ) ) , where d ≤ w ≤ n . Thus, our scheme is asymptotically faster for all codes with a < 2 . This speedup is achieved by developing techniques that enable parallelized code surgery under constant qubit overhead and leverage classical locally testable codes for efficient resource state preparation. These results establish a new paradigm for accelerating fault-tolerant quantum computation on qLDPC codes, while maintaining low overhead and broad applicability.

Alexey A. Kovalev, Leonid P. Pryadko