Quantum Surface Effects Enable Dissipationless Entanglement of Quantum Emitters Coupled via Surface Plasmon Polaritons

Core Concepts

Quantum surface effects in metal-dielectric nanostructures can be leveraged to create dissipationless entanglement between spatially separated quantum emitters coupled to a common surface plasmon polariton, paving the way for their use in quantum interconnects.

Abstract

Bibliographic Information: Liu, X.-Y., Yang, C.-J., & An, J.-H. (2024). Quantum surface effects on quantum emitters coupled to surface plasmon polariton. arXiv:2411.02990v1 [quant-ph].
Research Objective: This study investigates the impact of quantum surface effects (QSEs) on the interaction between multiple quantum emitters (QEs) and surface plasmon polaritons (SPPs) in a planar metal-dielectric nanostructure. The authors aim to determine if QSEs can mitigate the dissipation of QEs caused by lossy SPPs and enable the formation of entanglement between the QEs.
Methodology: The researchers employ a theoretical framework combining macroscopic quantum electrodynamics (QED) and the Feibelman d-parameter method. This approach allows them to model the non-Markovian dynamics of QEs coupled to a common SPP in the presence of QSEs, including nonlocal optical response, electron spill-out, and Landau damping.
Key Findings:

QSEs modify the spectral density of the system, leading to a red shift, broadening of the plasmon resonance peak, and the emergence of a high-frequency shoulder.
The presence of QSEs facilitates the formation of bound states in the energy spectrum of the total QE-SPP system.
When bound states are formed, the dissipation of the QEs is suppressed, and a coherent quantum correlation is established between them.
In the case of two QEs, the presence of one bound state leads to stable entanglement, while two bound states result in a persistently oscillating entanglement, indicating a lossless energy exchange mediated by the SPP.
Main Conclusions: The study demonstrates that QSEs can be harnessed to overcome the detrimental effects of dissipation in QE-SPP systems. The formation of bound states due to QSEs enables the creation of dissipationless entanglement between spatially separated QEs, suggesting a potential avenue for realizing robust quantum interconnects based on SPPs.
Significance: This research provides valuable insights into the complex interplay between QSEs and light-matter interactions at the nanoscale. The findings have significant implications for the development of quantum plasmonic devices, particularly for applications in quantum information processing and communication.
Limitations and Future Research: The study focuses on a simplified planar geometry. Further research could explore the influence of more complex nanostructures and material properties on the observed phenomena. Experimental validation of the theoretical predictions would be crucial for advancing the field.

Stats

The enhancement of J0(ω) over the spontaneous emission rate in free space is five orders of magnitude when z0 reaches the nanoscale.

Key Insights Distilled From

Quantum surface effects on quantum emitters coupled to surface plasmon polariton

by Xin-Yue Liu,... at arxiv.org 11-06-2024

https://arxiv.org/pdf/2411.02990.pdf

Deeper Inquiries

How would the incorporation of multiple SPP modes or different plasmonic waveguide geometries affect the entanglement generation and dissipation properties of the system?

Incorporating multiple SPP modes or different plasmonic waveguide geometries would significantly impact the entanglement generation and dissipation properties of the system, introducing both opportunities and challenges:
Multiple SPP Modes:

Enhanced Entanglement: Multiple SPP modes can provide additional channels for mediating interactions between quantum emitters (QEs). This could lead to the generation of higher-dimensional entanglement or faster entanglement generation rates due to the increased coupling possibilities.
Mode Dispersion and Interference: Different SPP modes generally have distinct dispersion relations, meaning their propagation speeds vary with frequency. This can lead to entanglement degradation over time due to the different arrival times of photons emitted into different modes. Additionally, interference between multiple modes could either enhance or suppress the overall coupling strength, depending on the specific configuration.
Different Plasmonic Waveguide Geometries:

Tailored SPP Dispersion: The dispersion relation of SPPs is highly sensitive to the geometry of the plasmonic waveguide. By carefully designing the waveguide shape, it's possible to engineer the SPP dispersion to match the emission frequencies of the QEs, thereby optimizing the coupling strength and minimizing dispersion-induced entanglement degradation.
Field Confinement and Purcell Enhancement: Different waveguide geometries offer varying degrees of SPP field confinement. Tighter confinement generally leads to stronger light-matter interactions and enhanced Purcell factors, which can accelerate entanglement generation but also increase the sensitivity to loss mechanisms.
Fabrication Complexity: Fabricating complex plasmonic waveguide geometries with nanoscale precision can be challenging, potentially limiting the practical implementation of certain designs.
Overall:
Exploring multiple SPP modes and diverse waveguide geometries offers a rich landscape for manipulating QE entanglement. However, careful optimization is crucial to balance the benefits of enhanced coupling with the detrimental effects of dispersion and loss. Numerical simulations and experimental investigations are essential to identify optimal configurations for specific quantum information processing tasks.

Could the inherent losses associated with SPPs be exploited for specific quantum information processing tasks, such as quantum error correction or open system quantum simulation?

While often considered a drawback, the inherent losses associated with SPPs could potentially be harnessed for specific quantum information processing tasks:
Quantum Error Correction:

Dissipative Quantum Computing: Certain quantum error correction codes rely on engineered dissipation to drive the system towards a desired protected subspace. SPP losses could potentially be tailored to implement such dissipative elements in a quantum circuit, providing a natural mechanism for error suppression.
Error Detection: The sensitivity of SPP propagation to the local dielectric environment could be exploited for error detection. By monitoring changes in SPP transmission or reflection, it might be possible to infer the occurrence of errors in nearby qubits.
Open System Quantum Simulation:

Simulating Realistic Environments: Many physical systems of interest are inherently open, meaning they interact with their surroundings. SPP losses provide a natural platform for simulating such open system dynamics, where the environment is represented by the dissipative channels associated with the SPP modes.
Exploring Non-Markovian Effects: The strong coupling regime between QEs and SPPs often leads to non-Markovian dynamics, where the system retains memory of its past interactions with the environment. This memory effect can be exploited for specific quantum simulations, such as studying the dynamics of complex biological systems.
Challenges and Considerations:

Controlled Dissipation: Exploiting SPP losses for quantum information processing requires precise control over the dissipation channels. This necessitates advanced fabrication techniques and a deep understanding of the loss mechanisms at play.
Scalability: Integrating lossy SPP elements into larger-scale quantum circuits while maintaining the desired coherence properties remains a significant challenge.
Overall:
While challenging, harnessing SPP losses for quantum information processing presents intriguing possibilities. Further research is needed to develop robust methods for controlling and manipulating these losses, paving the way for novel quantum technologies based on open system dynamics.

If we consider the quantum emitters as nodes in a network, what are the potential advantages and challenges of using surface plasmon polaritons as the interconnecting channels compared to other approaches like photonic waveguides or superconducting circuits?

Using surface plasmon polaritons (SPPs) as interconnecting channels in a quantum network, where quantum emitters act as nodes, offers distinct advantages and challenges compared to established approaches like photonic waveguides or superconducting circuits:
Advantages of SPPs:

Miniaturization and Integration: SPPs confine light at the nanoscale, enabling significantly smaller device footprints compared to bulky photonic waveguides. This facilitates integration with existing semiconductor technologies and paves the way for highly compact quantum networks.
Strong Light-Matter Interactions: The subwavelength confinement of SPPs leads to strong light-matter interactions, enabling fast and efficient coupling between QEs and the SPP channels. This is crucial for achieving high-fidelity quantum state transfer and entanglement generation.
Tunable Optical Properties: The optical properties of SPPs can be readily tuned by adjusting the geometry and material properties of the plasmonic waveguides. This flexibility allows for tailoring the SPP dispersion and coupling strength to match the specific requirements of the quantum network.
Challenges of SPPs:

Propagation Losses: SPPs suffer from inherent propagation losses due to absorption and scattering in the metal, limiting the achievable communication distances. While the paper highlights strategies to mitigate these losses, they remain a significant hurdle for long-distance quantum communication.
Scalability and Complexity: Fabricating and integrating complex plasmonic waveguide networks with multiple QEs while maintaining low loss and high fidelity poses significant technological challenges.
Room-Temperature Operation: While progress has been made, achieving robust SPP-based quantum networks at room temperature remains challenging due to increased losses and decoherence at higher temperatures.
Comparison to Other Approaches:

Photonic Waveguides: Offer lower losses and longer propagation distances but lack the miniaturization potential and strong light-matter interactions of SPPs.
Superconducting Circuits: Excel in coherence times and controllability but operate at cryogenic temperatures and face challenges in optical interfacing for long-distance communication.
Overall:
SPP-based quantum networks hold promise for realizing compact, integrated systems with strong light-matter interactions. However, overcoming propagation losses and scalability challenges is crucial for their widespread adoption. Combining the strengths of SPPs with other approaches, such as hybrid photonic-plasmonic systems, could offer a pathway towards practical and scalable quantum networks.