[Paper Review] Quantum Electrometer for Time-Resolved Material Science at the Atomic Lattice Scale

Gregor Pieplow, Cem Güney Torun+6 more|arXiv (Cornell University)|Jan 25, 2024

Diamond and Carbon-based Materials Research5 citations

TL;DR

The paper presents a quantum electrometer using a SnV color center in diamond to detect and localize single elementary charges at the lattice scale with sub-nanometer precision and time-resolved charge dynamics, enabling analysis of charge traps and spectral diffusion.

ABSTRACT

The detection of individual charges plays a crucial role in fundamental material science and the advancement of classical and quantum high-performance technologies that operate with low noise. However, resolving charges at the lattice scale in a time-resolved manner has not been achieved so far. Here, we present the development of an electrometer with 60 ns acquisition steps, leveraging on the spectroscopy of an optically-active spin defect embedded in a solid-state material with a non-linear Stark response. By applying our approach to diamond, a widely used platform for quantum technology applications, we can distinguish the distinct charge traps at the lattice scale, quantify their impact on transport dynamics and noise generation, analyze relevant material properties, and develop strategies for material optimization.

Motivation & Objective

• Enable time-resolved detection of individual charges with atomic-scale localization in a solid-state lattice.
• Quantify how nearby charge traps affect transport dynamics and noise in diamond-based materials.
• Develop strategies to optimize material quality by mapping trap densities and identities.
• Demonstrate a non-linear Stark-based sensing mechanism that suppresses background noise while achieving high spatial resolution.

Proposed method

• Utilize an inversion-symmetric, optically active SnV color center as a local electric-field sensor with a non-linear Stark response.
• Read out sensor states via photoluminescence excitation (PLE) spectroscopy to measure Stark shifts and infer local electric fields.
• Model the Stark shifts with a non-linear expansion that includes terms up to fourth order in E (Eq. 1) to relate shifts to trap-induced fields.
• Quantify trap proximity by comparing measured Stark shifts to Monte Carlo simulations of possible trap configurations (Fig. 2).
• Record time-resolved line scans to extract charge state transition probabilities p(i→j) and conditional transfer rates Γ_ct(i→j) for proximity traps (Fig. 3).
• Estimate trap densities ρ_trap by analyzing inhomogeneous broadening due to distant fluctuating charges (Fig. 4).

Figure 1: Working principle of the quantum electrometer. (a) The local probe is an optically-active atomic defect with non-linear Stark-sensitive energy-levels. The read-out unit is a photoluminescence excitation spectroscopy microscope. (b) A nearby charge shifts the optical transition from C 0 to

Experimental results

Research questions

• RQ1 Can a single inversion-symmetric color center resolve the position of nearby charge traps at lattice scale?
• RQ2 What are the dynamics and rates of charge ionization/neutralization for proximate traps under laser illumination?
• RQ3 How does local charge trap density ρ_trap influence spectral diffusion and optical coherence of the SnV sensor?
• RQ4 What material properties (e.g., vacancy complexes Vn) give rise to charge traps, and how can processing modulate them?
• RQ5 What guidelines emerge for designing materials and structures to minimize charge-noise in quantum technologies?

Key findings

• Relative electric-field sensitivity of about 1 in 10^7 enables Ångström-scale localization of nearby charges.
• Identified trap configurations around the SnV probe with nearest distances r1≈8 Å, r2≈11 Å, r3≈26 Å and remote trap density ρ_trap≈74(22) ppm.
• Observed charge-state lifetimes τ(SnV−⊙)=2.3(1) s and τ(SnV−□□)=4(1) s, indicating trap states are stable on seconds timescales.
• Demonstrated that bulk ρ_trap and surface trap densities can cause spectral broadening; thresholds suggest depths and geometries where broadening remains below 1% of the lifetime-limited 35 MHz linewidth.
• Found that Si implantation yields the lowest Vn-density among Si, Ge, Sn, suggesting material choice impacts vacancy complex formation.
• Provided a framework to predict spectral diffusion and quantify its impact on interference visibility and entanglement fidelity for quantum applications.

Figure 2: Lattice scale localization of charge traps. (a) Illustration of a diamond lattice including SnV and defects, identified as multi-vacancy complexes (V n ). Charges localized in these traps induce a Stark-shift of the energy levels of the atomic sensor probe. From very close to far, respecti