Hybrid quantum circuit with a superconducting qubit coupled to a spin ensemble

Area of Science:

• Quantum Computing
• Solid-State Physics
• Quantum Information Science

Background:

• Superconducting qubits are promising quantum computing platforms but require robust memory solutions.
• Nitrogen-vacancy (NV) centers in diamond offer a scalable solid-state spin ensemble with long coherence times.
• Hybrid quantum systems aim to leverage the strengths of different quantum technologies.

Purpose of the Study:

• To experimentally realize a hybrid quantum circuit integrating a superconducting qubit with a spin ensemble.
• To demonstrate the storage and retrieval of quantum information between these disparate quantum systems.
• To establish the feasibility of using spin ensembles as quantum memory for superconducting qubits.

Main Methods:

• Fabrication of a hybrid quantum circuit featuring a transmon-type superconducting qubit.
• Coherent coupling of the qubit to a nitrogen-vacancy (NV) center spin ensemble via a tunable superconducting resonator (quantum bus).
• Preparation of qubit superposition states, storage into collective spin ensemble excitations, and subsequent retrieval back into the qubit.

Main Results:

• Successful experimental realization of the hybrid quantum circuit.
• Demonstration of coherent information transfer between the superconducting qubit and the NV center spin ensemble.
• Observation of quantum state storage and retrieval, confirming the quantum memory functionality.

Conclusions:

• The study provides a proof of concept for spin-ensemble-based quantum memory for superconducting qubits.
• This hybrid approach offers a potential pathway for scalable quantum information storage.
• The demonstrated coherent coupling paves the way for advanced hybrid quantum information processing architectures.