Clustering Structure and Quantum Computing

Güleser Kalaycı Demir

Kai Zhang, Yu Guo, Jietai Jing

Abstract The universal quantum computation provides a new paradigm for information processing. One feasible approach is measurement‐based one‐way quantum computation utilizing cluster states. Generally, the generation of cluster states with different structures for implementing on‐demand quantum computation needs different experimental setup, which limits its scalability. Here, the reconfigurable hexapartite cluster states created by postprocessing the quadrature information of hexapartite entangled state are demonstrated. Without altering the experimental layout, nine quantum correlated states with different structures, especially three cluster states, are implemented. In particular, such method can effectively reduce the excess noise introduced by creating cluster states under limited squeezing resources. This approach provides an avenue for realizing large‐scale reconfigurable cluster states without changing the experimental architecture.

Davide Pastorello

Yujing Zhao, Xiongwen Chen, Zhengang Shi +3 more

We proposed an efficient scheme for implementing the large-scale one-way Quantum computing (QC) with a novel hybrid solid-state quantum system. This system consists of N Nitrogen-vacancy (N-V) centers coupled to N separate Transmission line resonators (TLRs), which are interconnected by a Current-biased Josephson junction (CBJJ) superconducting phase qubit. We showed the way of preparation of N-qubit linear cluster state with N N-V centers, then we demonstrated the way of extending cluster state by connecting two pieces of linear cluster states into two-dimensional cluster state, last, with our designed new structures, we demonstrated the QC basic operations. It means that our scheme may open up promising possibilities for implementing the practical and scalable one-way quantum computers with the hybrid solid-state quantum system. We discussed the experimental feasibility of our system.

Grier M. Jones, Hans‐Arno Jacobsen

To move towards the utility era of quantum computing, many corporations have posed distributed quantum computing (DQC) as a framework for scaling the current generation of devices for practical applications. One of these applications is quantum chemistry, also known as electronic structure theory, which has been poised as a “killer application” of quantum computing. To this end, we analyze five electronic structure methods, including the unitary coupled-cluster singles and doubles (UCCSD), unitary pair coupled-cluster doubles (UpCCD), unitary pair coupled-cluster with generalized singles and doubles (UpCCGSD), separable pair approximation plus generalized singles (SPA+GS), and local unitary cluster Jastrow (LUCJ) ansätze. The key benefit of these methods is that they can be found in common packages, such as Tequila and ffsim, that interface easily with the Qiskit Circuit Cutting addon. Herein, we highlight the challenges and aptitude of the aforementioned electronic structure methods for distribution using quasiprobability simulation with local operations (LO). The key findings of our work are that many of these algorithms cannot be efficiently parallelized using LO, and new methods must be developed to apply electronic structure theory within a DQC framework.

Yu-Hao Chen, Renata Wong

This work provides a step-by-step quantum computing derivation of the unitary coupled cluster singles and doubles ansatz. We show how the structure of the ansatz emerges from fermionic algebra under unitary constraints. By explicitly connecting second quantization, Jordan-Wigner mapping, and quantum circuit synthesis, we clarify conceptual gaps between quantum physics and quantum computing implementations, particularly regarding operator locality, commutation structure, and hardware realization. We exemplify the procedure on the singles and doubles coupled cluster ansatz for the hydrogen molecule.