Appearance of objectivity for NV centers interacting with dynamically polarized nuclear environment
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-03-18 |
| Journal | New Journal of Physics |
| Authors | Damian Kwiatkowski, Ćukasz CywiĆski, JarosĆaw K. Korbicz, Damian Kwiatkowski, Ćukasz CywiĆski |
| Institutions | Polish Academy of Sciences, QuTech |
| Citations | 7 |
| Analysis | Full AI Review Included |
Appearance of Objectivity in Dynamically Polarized NV Centers
Section titled âAppearance of Objectivity in Dynamically Polarized NV CentersâThis analysis summarizes the feasibility study of achieving Spectrum Broadcast Structures (SBS)âa strong indicator of quantum objectivityâusing Nitrogen-Vacancy (NV) centers in diamond, tailored for an engineering audience.
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Numerical analysis confirms that NV centers in diamond can simulate the emergence of quantum objectivity (SBS formation) under experimentally viable conditions.
- Feasibility Condition: SBS formation requires high polarization (p > 0.5) of the nearest 13C nuclear spins, typically achieved via Dynamic Nuclear Polarization (DNP).
- Critical Magnetic Field: The process is robust only at relatively low external magnetic fields (B †20 Gauss), where the qubit-nuclear coupling energy scale exceeds the nuclear Zeeman energy scale.
- Required Environment Size: Objectivity is achieved when the observed environment (macrofraction) consists of at least 10 highly polarized, strongly coupled nuclear spins.
- Timescale: The state of the NV center and its nearest polarized environment approaches an SBS state within approximately 100 ”s.
- Significance: This work generalizes previous theoretical models by including non-trivial environment dynamics (Zeeman precession) and validates NV centers as a realistic platform for studying the quantum-to-classical transition.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Qubit Definition | m=0 and m=1 | N/A | Ground state manifold of the NV center (S=1). |
| NV Zero-Field Splitting (Î0) | 2.87 | GHz | Energy gap between m=0 and m=±1 states. |
| Electron Gyromagnetic Ratio (Îłe) | 28.07 | GHz/T | Used for calculating electron Zeeman splitting. |
| 13C Gyromagnetic Ratio (Îł13C) | 10.71 | MHz/T | Used for calculating nuclear Zeeman splitting (Ï). |
| Critical Magnetic Field (B) | †20 | Gauss | Required for strong coupling (A > Ï) necessary for SBS. |
| Minimum Nuclear Polarization (p) | > 0.5 | N/A | Required polarization degree for the observed environment (DNP region). |
| Observed Macrofraction Size (”N) | 10 to 20 | Spins | Minimum number of polarized spins required per independent observer. |
| Total Simulated Environment Size (N) | 400 | Spins | Total number of 13C nuclei considered in the bath. |
| SBS Formation Timescale | ~100 | ”s | Time required for conditional state fidelity to decay to zero. |
| 13C Natural Concentration | ~1.1 | % | Density of spinful nuclei in the diamond lattice. |
| Qubit-Nuclear Coupling | Dipolar (1/r3) | N/A | Anisotropic coupling mechanism dominating at distances > 0.5 nm. |
Key Methodologies
Section titled âKey MethodologiesâThe study relies on numerical simulations of the NV center central spin model under specific initial conditions achievable through state-of-the-art DNP techniques.
- System Hamiltonian: The system is modeled using a pure dephasing Hamiltonian (Ä€ = Ä€Q + Ä€E + ĆzV), where the NV qubit (Ä€Q) interacts with the 13C nuclear spin environment (Ä€E) via dipolar coupling (V).
- Environment State Preparation (DNP): The environment is partitioned into two parts:
- Observed Fraction (fE): Nuclear spins closest to the NV center (within radius rp) are highly polarized (p â„ 0.9) to simulate DNP success.
- Unobserved Fraction ((1-f)E): Remaining nuclei are assumed completely mixed (p=0), corresponding to room temperature thermal equilibrium.
- Coarse-Graining for Objectivity: The observed fraction (fE) is mathematically divided into M equal-sized macrofractions (”N = 5, 10, or 20 spins), representing independent observers accessing the information.
- Decoherence Analysis: The decoherence factor (Îł(t)) due to the unobserved, mixed environment is calculated. SBS requires this factor to vanish, ensuring the qubit state is fully decohered into the pointer basis.
- Objectivity Verification (Fidelity): The core metric for SBS is the fidelity (F) between the conditional states of the macrofractions (Ïm and Ïmâ). SBS is confirmed when F approaches zero, indicating perfect distinguishability (orthogonality) between the environmental states conditioned on the qubitâs pointer state.
- Parameter Sweep: Simulations were performed across different magnetic fields (10 Gs to 100 Gs) and polarization degrees (p = 0.1, 0.5, 1.0) to identify the optimal regime for SBS formation.
Commercial Applications
Section titled âCommercial ApplicationsâThe findings directly support the development and optimization of quantum technologies based on solid-state NV centers in diamond.
- Solid-State Quantum Computing: NV centers are leading candidates for robust, room-temperature qubits. Achieving SBS is crucial for understanding and engineering reliable quantum memory and readout protocols.
- Quantum Sensing and Metrology: The ability to control and read out the state of small, highly polarized nuclear spin clusters is fundamental to high-sensitivity magnetometry and nanoscale Nuclear Magnetic Resonance (NMR).
- High-Resolution Nanoscale NMR: NV centers can be used to sense and characterize the spin state of molecules or proteins placed near the diamond surface, enabling chemical analysis at the single-molecule level.
- Quantum Network Development: The techniques used for polarizing and controlling nuclear spins are essential for creating and maintaining entangled states between distant NV centers, a requirement for quantum repeaters and networks.
- Fundamental Physics Simulators: NV systems serve as highly controllable platforms for experimentally verifying complex quantum phenomena, such as the quantum-to-classical transition and the emergence of objective reality.
View Original Abstract
Abstract Quantum-to-classical transition still eludes a full understanding. Out of its multiple aspects, one has recently gained an increased attentionâthe appearance of objective world out of the quantum. One particular idea is that objectivity appears thanks to specific quantum state structures formation during the evolution, known as spectrum broadcast structures (SBS). Despite that quite some research was already performed on this strong and fundamental form of objectivity, the practical realization of SBS in a concrete physical medium has not been explicitly analyzed so far. In this work, we study the possibility to simulate objectivization process via SBS formation using widely studied nitrogen-vacancy centers in diamonds. Assuming achievable limits of dynamical polarization technique, we show that for high, but experimentally viable polarizations ( p > 0.5) of nuclear spins and for magnetic fields lower than â20 G the state of the NV center and its nearest polarized environment approaches an SBS state reasonably well.