[Paper Review] Coherent Control of Spins with Gaussian Acoustics

Samuel J. Whiteley, Gary Wolfowicz+12 more|arXiv (Cornell University)|Apr 29, 2018

Mechanical and Optical Resonators32 references3 citations

TL;DR

This paper demonstrates universal coherent control of divacancy spin qubits in silicon carbide using Gaussian surface acoustic waves, leveraging shear and longitudinal mechanical modes to induce spin transitions. It achieves Autler-Townes splitting, Rabi oscillations, and direct optical detection of acoustic paramagnetic resonance, enabling full mechanical control over spin states with potential for quantum nanomechanical integration.

ABSTRACT

Hybrid quantum systems combine the advantages of dissimilar quantum degrees of freedom to solve challenges of communicating between disparate quantum states. Silicon carbide (SiC) is an exemplary platform for hybrid spin-mechanical systems, providing long-lived spin registers within optically-active defects, wafer-scale availability, and low acoustic losses. Past demonstrations of spin-mechanical coupling have used uniaxial strain to drive magnetically forbidden spin transitions. With a Gaussian surface acoustic wave resonator, here we show universal control of divacancy spin qubits using all mechanical degrees of freedom, especially shear. We demonstrate Autler-Townes splitting, coherent mechanically driven Rabi oscillations, and direct optical observation of acoustic paramagnetic resonance. This work expands the versatility of mechanically driven spins and shows promise towards integrating spins with quantum nanomechanical systems.

Motivation & Objective

• To achieve universal control of spin qubits in silicon carbide using mechanical degrees of freedom.
• To overcome limitations of uniaxial strain in driving magnetically forbidden spin transitions.
• To demonstrate coherent coupling between spin qubits and multiple mechanical modes, especially shear.
• To enable optical detection of mechanically driven spin transitions for quantum sensing and control.

Proposed method

• Utilization of a Gaussian surface acoustic wave resonator to generate tailored mechanical modes in silicon carbide.
• Employment of shear and longitudinal acoustic modes to coherently drive spin transitions in divacancy defects.
• Implementation of microwave and optical techniques to probe spin dynamics and detect paramagnetic resonance.
• Use of Autler-Townes spectroscopy to resolve mechanical coupling to spin states.
• Real-time monitoring of Rabi oscillations via optical readout to confirm coherent control.
• Exploitation of low acoustic loss and wafer-scale compatibility of SiC for scalable quantum systems.

Experimental results

Research questions

• RQ1 Can Gaussian surface acoustic waves enable coherent control of spin qubits in silicon carbide beyond uniaxial strain?
• RQ2 To what extent can shear and longitudinal mechanical modes drive magnetically forbidden spin transitions?
• RQ3 Can acoustic paramagnetic resonance be directly observed optically in a spin-mechanical system?
• RQ4 What is the coherence and fidelity of mechanically driven Rabi oscillations in this platform?
• RQ5 How scalable and integrable is this approach for hybrid quantum nanomechanical systems?

Key findings

• Autler-Townes splitting was observed, confirming coherent coupling between spin qubits and mechanical modes.
• Coherent mechanically driven Rabi oscillations were demonstrated, indicating high-fidelity control of spin states.
• Direct optical observation of acoustic paramagnetic resonance was achieved, validating the mechanical driving mechanism.
• Shear acoustic modes were shown to effectively drive spin transitions, expanding the range of accessible control.
• The system exhibited low acoustic losses and long spin coherence, enabling stable quantum operations.
• Universal control over spin qubits was realized using all mechanical degrees of freedom, including shear, enhancing system versatility.