Long-range quantum entanglement in dielectric mu-near-zero metamaterials
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-09-03 |
| Journal | Light Science & Applications |
| Authors | Olivia Mello, Larissa Vertchenko, Seth Nelson, Adrien Debacq, Durdu Ă. GĂŒney |
| Institutions | University of Namur, Harvard University |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research proposes and validates a novel, fully dielectric Mu Near-Zero (MNZ) metamaterial platform for achieving robust, long-range quantum entanglement on a chip, overcoming the limitations of lossy plasmonic systems.
- Core Achievement: Demonstrated sustained quantum entanglement (high concurrence C) over 17 free-space wavelengths (approximately 12.5 ”m) between two quantum emitters.
- Platform: A fully dielectric MNZ metamaterial composed of a 2D square lattice of diamond pillars, compatible with Silicon Vacancy (SiV) centers.
- Performance Enhancement: Achieved an order of magnitude enhancement in entanglement range compared to previous proposals using plasmonic Epsilon Near-Zero (ENZ) waveguides.
- Mechanism: The MNZ structure mediates interactions by stretching the effective wavelength (neff approaches zero), leading to extended coherence length and strong cooperative decay (Î12) over large spatial separations.
- Steady-State Entanglement: By applying an external pump source, the system maintains high steady-state concurrence (upwards of 0.35), correlated with an antibunching signature (g(2)(0) close to zero).
- Robustness: Simulations show the MNZ behavior is maintained even under random fabrication perturbations (±5 nm variation in pillar radius), crucial for experimental implementation.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Metamaterial Type | Mu Near-Zero (MNZ) | N/A | Fully dielectric, 2D square lattice |
| Material | Diamond (n = 2.4064) | N/A | Host material for SiV centers |
| Operating Wavelength (λ0) | 737 | nm | Zero-Phonon Line (ZPL) of SiV center |
| Lattice Period (a) | 505 | nm | Pitch of the square lattice |
| Pillar Radius (r) | 115 | nm | Radius of the diamond pillars |
| Effective Refractive Index (neff) | -0.03 | N/A | Minimum absolute value at 737 nm |
| Effective Impedance (Z) | 0.2 | N/A | Low, non-zero impedance (Z = sqrt(”/Δ)) |
| Purcell Factor (Fp) | 7 | N/A | Modest enhancement at the ” near-zero crossing |
| Maximum Entanglement Range | 17 λ0 (12.5 ”m) | Wavelengths (”m) | Sustained high transient concurrence |
| Maximum Steady-State Concurrence (Css) | ~0.4 | N/A | Achieved under antisymmetric pumping (Ω1 = -Ω2) |
| Temporal Decay Time (Steady State) | yt = 20 | Normalized time | Time required to reach steady-state concurrence |
Key Methodologies
Section titled âKey MethodologiesâThe research relies on a combination of numerical simulations (COMSOL Multiphysics, Ansys Lumerical FDTD) and analytical modeling using the Lindblad master equation.
- Metamaterial Design and Simulation:
- A 2D square lattice of diamond pillars was designed to achieve MNZ behavior (Re ”r crosses zero) at the SiV ZPL (737 nm).
- Full-wave numerical simulations (FDTD) were used to calculate the magnetic field (Hz) distribution for the Transverse Electric (TE) monopole mode.
- Parameter Retrieval:
- The effective constitutive parameters (Δr and ”r) and effective index (neff) were retrieved using the transfer matrix method based on transmitted and reflected fields.
- Quantum Coupling Calculation:
- The cooperative decay rate (Î12) and the coherent dipole-dipole coupling (g12) were calculated from the imaginary and real components of the Greenâs tensor, which is derived from the simulated Hz fields.
- A magnetic dipole source was swept across the metamaterial structure (up to 25 pitches) to map the coupling parameters as a function of inter-emitter separation (r12).
- Quantum Dynamics Modeling:
- The quantum dynamics of the two-qubit system were modeled using the Lindblad master equation, incorporating the calculated Î12 and g12 values.
- Transient Concurrence: Calculated using the analytical solution for the density matrix elements (Eq. 11) assuming a single initial excitation.
- Steady-State Concurrence: Calculated by solving the full system of 16 coupled differential equations (including external pump terms Ωi) until the density matrix reached equilibrium (yt = 90).
- Correlation Analysis:
- The zero time delay second-order correlation function g(2)(0) was calculated from the steady-state density matrix to confirm antibunching signatures correlated with high entanglement.
- Robustness Testing:
- Simulations were performed with random perturbations (±2 nm and ±5 nm) applied to the pillar radius to verify that the near-zero refractive index behavior was maintained, confirming fabrication tolerance.
Commercial Applications
Section titled âCommercial ApplicationsâThe development of robust, long-range entanglement mediation on a fully dielectric, low-loss platform is critical for scaling quantum technologies.
- Quantum Computing (On-Chip): Enables the construction of large-area distributed quantum computing architectures and cluster states by maintaining strong qubit interactions over distances far exceeding the free-space wavelength.
- Quantum Communication and Networks: Facilitates the development of on-chip quantum repeaters with reduced overhead, extending the practical range of quantum communication systems.
- Quantum Sensing and Metrology: The diamond platform (SiV centers) is highly relevant for high-fidelity quantum sensing applications, where maintaining coherence and entanglement over larger areas is beneficial.
- Photonic Integrated Circuits (PICs): The use of all-dielectric metamaterials, compatible with standard CMOS fabrication techniques (as suggested by the use of thin-film diamond on silicon substrates), supports scalable integration of quantum components into PICs.
- Zero-Index Photonics: Advances the fundamental understanding and application of MNZ structures, which are useful for supercoupling, cloaking, and impurity-immunity in optical systems.
View Original Abstract
Abstract Entanglement is paramount in quantum information processing. Many quantum systems suffer from spatial decoherence in distances over a wavelength and cannot be sustained over short time periods due to dissipation. However, long range solutions are required for the development of quantum information processing on chip. Photonic reservoirs mediating the interactions between qubits and their environment are suggested. Recent research takes advantage of extended wavelength inside near-zero refractive index media to solve the long-range problem along with less sensitivity on the position of quantum emitters. However, those recent proposals use plasmonic epsilon near-zero waveguides that are intrinsically lossy. Here, we propose a fully dielectric platform, compatible with the Nitrogen Vacancy (NV) diamond centers on-chip technology, to drastically improve the range of entanglement over 17 free-space wavelengths, or approximatively 12.5 ”m, using mu near-zero metamaterials. We evaluate transient and steady state concurrence demonstrating an order of magnitude enhancement compared to previous works. This is, to the best of our knowledge, the first time that such a long distance is reported using this strategy. Moreover, value of the zero time delay second order correlation function $${g}_{12}^{(2)}(0)$$ <mml:math xmlns:mml=âhttp://www.w3.org/1998/Math/MathMLâ> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>12</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>(</mml:mo> <mml:mn>2</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:msubsup> <mml:mo>(</mml:mo> <mml:mn>0</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> are provided, showing antibunching signature correlated with a high degree of concurrence.