Efficient fault-tolerant quantum computing

I. S. Osborne

Yutaro Akahoshi, Jun Fujisaki, Hirotaka Oshima +2 more

Quantum computers hold the promise of revolutionizing several computational tasks by significantly enhancing their calculation speed compared to classical computers. However, there is still a large gap towards fault-tolerant quantum computing (FTQC) due to the large requirement of physical qubits. Under these circumstances, authors proposed a partially fault-tolerant quantum computing architecture that consists of the fault-tolerant Clifford gates and the sufficiently clean analog rotation gate, named “Space-Time efficient Analog Rotation gate quantum computing architecture (STAR architecture).” Although its theoretical foundation is given, we need to develop an efficient software implementation tailored for STAR architecture due to its unique choice of the fundamental gate set. In this study, we construct an integrated software system of STAR-architecture-based quantum computation, which generates physical instructions executable on quantum devices from input logical quantum circuits. The system mainly consists of two parts, a circuit converter and an operation controller. The circuit converter comprises a set of conversion subroutines, which bridge several instruction layers: logical circuit layer, lattice surgery layer, and physical circuit layer. The operation controller efficiently executes the generated instructions. Especially, it enables efficient treatment of the analog rotation gate, which needs real-time scheduling of running instructions due to its probabilistic nature.

Alexander M. Dalzell, Sam McArdle, Mario Berta +10 more

Yuuki Tokunaga

This article introduces new approaches to develop early fault-tolerant quantum computing (early-FTQC) such as improving efficiency of quantum computation on encoded data, new circuit efficiency techniques for quantum algorithms, and combining error-mitigation techniques with fault-tolerant quantum computation.

Soshun Naito, Yasunari Suzuki, Yuuki Tokunaga

In fault-tolerant quantum computing, a large number of physical qubits are required to construct a single logical qubit, and a single quantum node may be able to hold only a small number of logical qubits. In such a case, the idea of distributed fault-tolerant quantum computing (DFTQC) is important to demonstrate large-scale quantum computation using small-scale nodes. However, the design of distributed systems on small-scale nodes, where each node can store only one or a few logical qubits for computation, has not been explored well yet. In this paper, we propose network-based quantum computation (NBQC) to efficiently realize distributed fault-tolerant quantum computation using many small-scale nodes. A key idea of NBQC is to let computational data continuously move throughout the network while maintaining the connectivity to other nodes. We numerically show that, for practical benchmark tasks, our method achieves shorter execution times than circuit-based strategies and more node-efficient constructions than measurement-based quantum computing. Also, if we are allowed to specialize the network to the structure of quantum programs, such as peak access frequencies, the number of nodes can be significantly reduced. Thus, our methods provide a foundation in designing DFTQC architecture exploiting the redundancy of many small fault-tolerant nodes.

Yasunari Suzuki