A quantum coherent spin in a two-dimensional material at room temperature (2306.13025v1)

Abstract: Quantum networks and sensing require solid-state spin-photon interfaces that combine single-photon generation and long-lived spin coherence with scalable device integration, ideally at ambient conditions. Despite rapid progress reported across several candidate systems, those possessing quantum coherent single spins at room temperature remain extremely rare. Here, we report quantum coherent control under ambient conditions of a single-photon emitting defect spin in a a two-dimensional material, hexagonal boron nitride. We identify that the carbon-related defect has a spin-triplet electronic ground-state manifold. We demonstrate that the spin coherence is governed predominantly by coupling to only a few proximal nuclei and is prolonged by decoupling protocols. Our results allow for a room-temperature spin qubit coupled to a multi-qubit quantum register or quantum sensor with nanoscale sample proximity.

• The paper demonstrates room-temperature coherent control of spin-triplet carbon-related defects in hBN.
• The authors employ ODMR and Ramsey interferometry to achieve key metrics including T*_2 of ~100 ns and Rabi coherence time exceeding 1.2 μs.
• The findings pave the way for scalable quantum devices and enhanced quantum sensing applications in 2D materials.

Insights into Quantum Coherent Spins in 2D Materials at Room Temperature

The research paper addresses the development of quantum coherent spin-photon interfaces in two-dimensional materials, specifically hexagonal boron nitride (hBN), operational at room temperature. This paper represents a significant step in quantum technology advancement, as these spin-photon interfaces are pivotal for quantum networking and sensing applications.

Key Contributions

The paper demonstrates the coherent control of a quantum spin defect in hBN at room temperature, a notable accomplishment given the scarcity of materials that can maintain quantum coherence under such conditions. The identified carbon-related defect within hBN possesses a spin-triplet (S = 1) electronic ground-state manifold. The spin coherence is manipulated primarily through interaction with a limited number of proximal nuclei, and its longevity is extended via decoupling protocols. This spin qubit, operable at ambient temperatures, represents a prime candidate for integration into scalable quantum devices owing to its nanoscale proximity capabilities.

Experimental Findings

The paper successfully identifies and characterizes the carbon-based defects in hBN, which emit photons primarily in the visible spectrum (~600 nm) and exhibit detectable spin signatures via optically detected magnetic resonance (ODMR). The observed defects show a zero-field splitting of 1.96 GHz, confirmable through angle-resolved magneto-optical measurements, and a defined low-symmetry chemical structure. The research employs Ramsey interferometry, indicating an inhomogeneous dephasing time (T$^*_2$) of ~100 ns. Additionally, the continuously driven Rabi coherence time (T$_{\text{Rabi}}$) exceeds 1.2 μs at room temperature, pointing to effective protection of the electronic spin from environmental decoherence, mainly attributed to interaction with local nuclei.

Implications and Future Speculations

The identification and characterization of these spin-triplet defects in hBN open several avenues for quantum technology advancement. The paper's findings suggest the potential for implementing such defects in scalable quantum repeater hardware, operating at ambient conditions, which is critical for expanding quantum networks. Given hBN's versatility as a layered material, the research foresees potential applications in nano-engineering and quantum sensing. The proximity of the defects to surface levels in hBN could make them highly sensitive nanoscale sensors, with capabilities likened to nitrogen-vacancy (NV) centers in diamond yet without similar degradation issues.

Sensing applications could leverage the dynamic flexibility and resilience of these defects under various vector magnetic field strengths, thus broadening the scope of practical quantum sensors. Moreover, this work lays the groundwork for future studies that could explore further defect engineering and integration strategies to enhance the optical and quantum coherence properties essential for the next generation of quantum devices.

In conclusion, the paper provides substantive insights into the properties and potential applications of coherent spin defects in hBN, elaborating on their operational methodologies, effectiveness of coherence times, and fundamental structural characteristics. Future research will undoubtedly explore material optimization, defect control, and broader integration strategies to harness these findings in practical quantum systems.