Fusing the single-excitation subspace with [Formula: see text]

Area of Science:

• Quantum Computing
• Quantum Information Processing
• Superconducting Qubits

Background:

• Noisy intermediate-scale quantum (NISQ) processors lack full error correction, limiting practical applications.
• Gate-model quantum algorithms struggle with fidelity as problem size and circuit depth increase.
• Non-gate-model approaches like analog quantum simulation and quantum annealing have specific hardware needs.

Purpose of the Study:

• To develop a scalable approach for near-term quantum processors by enhancing the single-excitation subspace (SES) method.
• To reduce the exponential resource costs associated with ancillary qubits in the SES method.
• To enable a hybrid quantum computation model for efficient algorithm implementation.

Main Methods:

• Proposed a hybrid quantum computation by fusing the SES method with a multi-ancilla Hilbert space.
• Implemented the tensor product of an SES register with ancilla qubits for controlled arbitrary unitary operations.
• Developed constant-depth algorithmic components for data processing and ancilla-based control.

Main Results:

• Circumvented the exponential resource scaling issue of the SES method with ancillary qubits.
• Demonstrated a hybrid computation model integrating SES operations, traditional gates, and controlled-unitaries.
• Successfully implemented ancilla-assisted quantum phase estimation and the Harrow-Hassidim-Lloyd quantum linear system solver.

Conclusions:

• The proposed hybrid approach offers a scalable and efficient solution for NISQ devices.
• This method enables practical applications of quantum computing by overcoming limitations of existing techniques.
• Facilitates the development of advanced quantum algorithms on near-term quantum hardware.