Efficient multi-qubit subspace rotations via topological quantum walks

Abstract

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.

14 pages, 7 figures, expanded version

References in corpus (7)

• Microwave photonics with superconducting quantum circuits
• Exploring Topological Phases With Quantum Walks
• Universal computation by multi-particle quantum walk
• Observation of Berry's Phase in a Solid State Qubit
• A Grand Unification of Quantum Algorithms
• Fast multi-qubit gates through simultaneous two-qubit gates
• Hamiltonian singular value transformation and inverse block encoding

Cited by in corpus (2)

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