Single-Photon Switching and Entanglement of Solid-State Qubits in an Integrated Nanophotonic System (1608.05147v1)

Abstract: Efficient interfaces between photons and quantum emitters form the basis for quantum networks and enable nonlinear optical devices operating at the single-photon level. We demonstrate an integrated platform for scalable quantum nanophotonics based on silicon-vacancy (SiV) color centers coupled to nanoscale diamond devices. By placing SiV centers inside diamond photonic crystal cavities, we realize a quantum-optical switch controlled by a single color center. We control the switch using SiV metastable orbital states and verify optical switching at the single-photon level by using photon correlation measurements. We use Raman transitions to realize a single-photon source with a tunable frequency and bandwidth in a diamond waveguide. Finally, we create entanglement between two SiV centers by detecting indistinguishable Raman photons emitted into a single waveguide. Entanglement is verified using a novel superradiant feature observed in photon correlation measurements, paving the way for the realization of quantum networks.

• The paper integrates SiV centers in diamond photonic crystal cavities to create a scalable platform for controlled single-photon switching.
• The paper realizes a quantum-optical switch with high extinction ratios by harnessing the metastable orbital states of individual SiV centers.
• The paper achieves tunable single-photon sources and entangles multiple SiV centers via Raman transitions, paving the way for advanced quantum networks.

Single-Photon Switching and Entanglement in Integrated Nanophotonic Systems

The paper "Single-Photon Switching and Entanglement of Solid-State Qubits in an Integrated Nanophotonic System" explores the development of scalable quantum nanophotonic interfaces, leveraging silicon-vacancy (SiV) color centers within diamond-based structures. This paper presents an advancement in achieving robust interactions between photons and quantum emitters, which are critical for realizing quantum networks and designing nonlinear optical devices that function at the single-photon level.

Key Contributions

1. Integration of SiV Centers in Nanophotonic Systems: The research highlights an integrated platform based on SiV centers within diamond photonic crystal cavities. These embedded sp-centers make it feasible to demonstrate controlled optical switching and single-photon source generation. The SiV color centers exhibit near lifetime-broadened optical transitions which substantially mitigate issues like spectral diffusion and inhomogeneous broadening due to environmental interactions.
2. Development of Single-Photon Switches: By utilizing the metastable orbital states of a single SiV center, the paper realizes a quantum-optical switch. This switch is manipulated at the single-photon level, verified through correlation measurements. The coupling between the SiV centers and photonic cavities results in high extinction ratios, showcasing effective interaction.
3. Tunable Single-Photon Source via Raman Transitions: The researchers employ Raman transitions in SiV centers to create a single-photon source with variable frequency and bandwidth, circumventing the limitations posed by spectral inhomogeneities. This tunability is critical for aligning quantum emitters in a network.
4. Entanglement of Multiple SiV Centers: A pioneering aspect of this work involves the generation of entanglement between two SiV centers through identical Raman photon emissions detected within a single waveguide. This entanglement is evidenced by photon correlation measurements demonstrating superradiant characteristics, setting a path forward for constructing more complex quantum networks.

Implications and Future Directions

The technological implications of this research are substantial for quantum information processing and communication. The integration of SiV centers into diamond nanostructures exhibits a notable progression towards achieving robust, scalable photonic quantum devices. The findings present three main implications:

• Practical Quantum Networks: The coherent integration of SiV centers and control over single-photon interactions may provide a foundational element for building large-scale quantum networks, where quantum nodes communicate through photonic interactions.
• Enhanced Device Efficiency: The system's ability to reduce losses associated with spectral diffusion and suppress decoherence offers a promising route to improve the efficiency of quantum optical devices beyond current solid-state systems.
• Improved Quantum Interfaces: Realizing high-cooperativity, SiV-integrated photonics opens pathways for deterministic quantum operations and enhanced coherence times, potentially enabling new quantum memory and computation paradigms.

Looking ahead, advancing the reported nanophotonic technology may involve optimizing emission properties and further integrating electronic spin states in configuration with photonic interactions. Moreover, scaling up the devices to support multiple interconnected qubits may provoke novel applications in quantum simulation and distributed quantum computing. The current research lays a groundwork that can stimulate future advancements within the rapidly evolving field of quantum nanophotonics.