[Paper Review] Constraints on a Spin-Dependent Exotic Interaction between Electrons with Single Electron Spin Quantum Sensors

Xing Rong, Man Jiao+7 more|arXiv (Cornell University)|Apr 19, 2018

Quantum and electron transport phenomena4 citations

TL;DR

This study establishes a new laboratory constraint on spin-dependent exotic interactions between electrons using single nitrogen-vacancy (NV) centers in diamond as quantum sensors. By detecting polarization signals from laser-pumped p-terphenyl doped with pentacene-d14, the authors set a 95% confidence upper bound of |g_A^e g_A^e / 4πℏc| ≤ 1.8×10⁻¹⁹ at a force range of 500 μm, improving previous limits by an order of magnitude and demonstrating NV centers as a powerful platform for probing new physics beyond the Standard Model.

ABSTRACT

A new laboratory bound on the axial-vector mediated interaction between electron spins at micrometer scale is established with single nitrogen-vacancy (NV) centers in diamond. A single crystal of $p$-terphenyl doped pentacene-$d_{14}$ under laser pumping provides the source of polarized electron spins. Based on the measurement of polarization signal via nitrogen-vacancy centers, we set a constraint for the exotic electron-electron coupling $g_A^eg_A^e$, within the force range from 10 to 900 $μ$m. The obtained upper bound of the coupling at 500 $μ$m is $|g_A^eg_A^e / 4π\hbar c |\leq 1.8 imes 10^{-19} $, which is one order of magnitude more stringent than a previous experiment. Our result shows that the NV center can be a promising platform for searching for new particles predicted by theories beyond the standard model.

Motivation & Objective

• To probe new spin-dependent forces between electrons predicted by theories beyond the Standard Model, such as axial-vector bosons and pseudoscalars.
• To establish tighter laboratory bounds on axial-vector mediated dipole-dipole interactions at micrometer-scale distances.
• To demonstrate the feasibility of using single NV centers in diamond as high-sensitivity quantum sensors for detecting weak spin-dependent interactions.
• To reduce systematic errors and improve signal-to-noise ratio through advanced control of laser pumping and dynamical decoupling sequences.

Proposed method

• Utilized single nitrogen-vacancy (NV) centers in diamond as quantum sensors to detect magnetic fields arising from polarized electron spins in a nearby source.
• Employed laser pumping of a p-terphenyl crystal doped with pentacene-d14 to generate a stable source of polarized electron spins.
• Measured the resulting phase shift in the NV center's quantum state via optically detected magnetic resonance to infer the strength of the spin-dependent interaction.
• Applied multipulse dynamical decoupling sequences to enhance coherence time and improve sensitivity to weak signals.
• Performed systematic error analysis accounting for crystal thickness, radius, relaxation time, and optical drift, with corrections applied to the final bound.
• Used a theoretical model of axial-vector mediated dipole-dipole interaction to relate measured phase shifts to coupling strength g_A^e g_A^e / 4πℏc.

Experimental results

Research questions

• RQ1 What is the tightest laboratory constraint on axial-vector mediated dipole-dipole interactions between electrons at micrometer-scale distances?
• RQ2 Can single NV centers in diamond detect weak spin-dependent forces from polarized electron sources at the 10–900 μm range?
• RQ3 How do systematic errors from experimental setup and material parameters affect the sensitivity and accuracy of the measurement?
• RQ4 To what extent can laser pumping and dynamical decoupling enhance the signal from polarized electron spins?
• RQ5 How does the NV sensor platform compare to other experimental methods in constraining exotic spin-dependent interactions?

Key findings

• The study establishes a new upper bound of |g_A^e g_A^e / 4πℏc| ≤ 1.8×10⁻¹⁹ at 500 μm with 95% confidence, representing a factor of 10 improvement over previous experiments.
• The constraint is most stringent in the 10–900 μm range, surpassing earlier limits from torsion pendulum and trapped ion experiments.
• Systematic corrections due to experimental drift and material parameters were quantified, with a total correction of -2.9(6.0)×10⁻²⁰ at 500 μm.
• The NV center platform demonstrated high sensitivity to weak spin-dependent forces, with a signal-to-noise ratio improved by laser pumping and dynamical decoupling.
• The method is scalable and can be extended to probe other spin-dependent interactions, such as monopole-dipole or dipole-dipole forces involving nucleons.
• Future improvements via higher laser power, multipulse sequences, and high-resolution imaging (e.g., NV-STED) could further enhance sensitivity by several orders of magnitude.