2021/11/12 by Xiu Gu, Jonathan Allcock, Gu, Xiu +5
Computer Science · Physics and Astronomy · #FOS: Physical sciences #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum Physics (quant-ph) #Quantum and electron transport phenomena
paper · pdf · doi:10.48550/arxiv.2111.06534
openalex publication_date 2021/11/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The rotation of subspaces by a chosen angle is a fundamental quantum computing operation, with applications in error correction and quantum algorithms such as the Quantum Approximate Optimization Algorithm, the Variational Quantum Eigensolver and the quantum singular value transformation. Such rotations are usually implemented at the hardware level via multiple-controlled-phase gates, which lead to large circuit depth when decomposed into one- and two-qubit gates. Here, we propose a fast, high-fidelity way to implement such operations via topological quantum walks, where a sequence of single-qubit z rotations of an ancilla qubit are interleaved with the evolution of a system Hamiltonian in which a matrix A is embedded. The subspace spanned by the left or right singular vectors of A with non-zero singular values is rotated, depending on the state of the ancilla. This procedure can be implemented in superconducting qubits, ion-traps and Rydberg atoms with star-type connectivity, significantly reducing the total gate time required compared to previous proposals.