Absorption-Based Spin Detection in Diamond NV Centers

Solution Overview

Problem

Current methods for detecting electronic spin states of nitrogen-vacancy (NV) centers in diamond, such as fluorescence-based detection, suffer from low sensitivity due to low photon collection efficiencies, with less than 1% of fluorescence falling within the collected solid angle.

Innovation Solution

An absorption-based detection system that measures changes in optical transmission through a bulk diamond sample by applying optical and microwave fields, utilizing a laser and microwave source to excite NV centers and detect the absorption intensity, which allows for determining the relative populations of spin states with higher sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If fluorescence-based detection is used to read out electronic spin states of NV centers, then the method is simple and well-established, but the photon collection efficiency is less than 1% resulting in low sensitivity

Engineering Contradiction:

Improvedetection sensitivityVSAvoidphoton collection efficiency

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent inverts the traditional fluorescence-based detection approach by using absorption-based detection instead. Rather than detecting emitted photons from NV centers, the system measures the absorption of incident laser light by NV centers in their ground state. This inversion fundamentally changes the detection mechanism from emission to absorption, achieving unity detection efficiency because all incident photons are potentially detectable through transmission measurements, eliminating the solid angle collection limitation of fluorescence methods.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If a small solid angle is used for photon collection, then the detection system is simple, but less than 1% of fluorescence photons are collected resulting in poor signal quality

Engineering Contradiction:

Improvesignal qualityVSAvoidcollection solid angle

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent inverts the traditional fluorescence-based detection approach by using absorption-based detection instead. Rather than detecting emitted photons from NV centers, the system measures the absorption of incident laser light by NV centers in their ground state. This inversion fundamentally changes the detection mechanism from emission to absorption, achieving unity detection efficiency because all incident photons are potentially detectable through transmission measurements, eliminating the solid angle collection limitation of fluorescence methods.

Inventive Principle:

Principle #13The other way round (Inversion)

3Productivity

If fluorescence detection is used, then the setup is straightforward, but the low photon collection efficiency requires long measurement times to achieve sufficient signal-to-noise ratio

Engineering Contradiction:

Improvemeasurement speedVSAvoidsignal-to-noise ratio

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent inverts the traditional fluorescence-based detection approach by using absorption-based detection instead. Rather than detecting emitted photons from NV centers, the system measures the absorption of incident laser light by NV centers in their ground state. This inversion fundamentally changes the detection mechanism from emission to absorption, achieving unity detection efficiency because all incident photons are potentially detectable through transmission measurements, eliminating the solid angle collection limitation of fluorescence methods.

Inventive Principle:

Principle #13The other way round (Inversion)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach achieves unity detection efficiency of absorbed photons, significantly improving signal contrast and sensitivity compared to traditional fluorescence-based methods, especially with higher optical and microwave excitation rates and increased optical depth.

Implementation Method 1

measuring the change in optical transmission through the bulk diamond sample due to optical absorption by NV centers

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Implementation Method 2

applying, during the optical excitation, microwave pulses that are resonant with electronic spin transitions of the spin impurities

Methodology Applied

Scientific EffectElectron spin resonance: Electron Paramagnetic Resonance

Data Source

PatentUS9658301B2Absorbtion-based detection of spin impurities in solid-state spin systems

Publication Date: 2017.05.23 PRESIDENT & FELLOWS OF HARVARD COLLEGE

AI summary

Absorption based detection of spin states of spin impurities within a solid-state spin system, such as NV centers in diamond, is implemented by measuring the absorption intensity of an optical signal applied to the spin impurities, i.e. change in intensity of the optical signal after the signal has been transmitted through the solid-state spin system. During optical excitation of the spin impurities, microwave pulses are applied to the sample at a frequency tuned to the ESR frequency. The relative populations of the spin states of the impurities, which provides information regarding variables of interest such as an external magnetic field or a quantum information protocol, is determined from the ratio of the absorption intensity of the optical signal when the microwave pulses are turned on, to the absorption intensity of the optical signal when the microwave pulses turned off.