Quantum Dot Charge Sensor With Parallel Inductor Resonance

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Solution Overview

Problem

Conventional charge sensors using quantum dots are not sensitive enough for accurately measuring minute changes in charge, particularly when using high-frequency signals.

Innovation Solution

A charge sensor configuration incorporating a quantum dot connected via tunnel junctions to input and output terminals, with an inductor in parallel, allowing for sensitive detection of charge changes by measuring reflection and passing amplitudes and phases of high-frequency signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional high-frequency signal methods are used to measure minute charge changes, then measurement sensitivity is improved compared to current measurement, but the sensitivity is still insufficient for accurate quantum state reading

Engineering Contradiction:

Improvecharge detection sensitivityVSAvoidmeasurement accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies resonance oscillation of the quantum dot system at a specific frequency to amplify the response to charge changes. By tuning the measurement frequency to match the resonant frequency of the quantum dot-capacitor system, small charge variations produce large oscillation amplitude changes, significantly enhancing detection sensitivity and resolving the insufficiency of conventional high-frequency methods.

Inventive Principle:

Principle #18Mechanical vibration

Solution Approach 2:

The patent changes the operating parameters by using AC voltage signals at resonant frequencies rather than DC or arbitrary frequency AC signals. This parameter change transforms the system response from linear and insensitive to resonant and highly sensitive, enabling accurate detection of minute charge changes in quantum dots.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the number of electrons in the silicon quantum dot is kept small to maintain quantum properties, then quantum behavior is preserved, but the current value becomes too small for reliable measurement

Engineering Contradiction:

Improvequantum state integrityVSAvoidcurrent measurement capability

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent replaces direct current measurement (electrical measurement) with resonance amplitude measurement (mechanical oscillation measurement). By measuring the oscillation amplitude of the quantum dot system at resonance rather than the tiny current directly, the system maintains quantum integrity with few electrons while achieving reliable detection through amplified mechanical-like oscillation responses.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If another silicon quantum dot is used as a charge sensor disposed in the vicinity, then charge sensing capability is enabled through capacitive coupling, but the sensitivity is limited and device complexity increases

Engineering Contradiction:

Improvecharge sensing capabilityVSAvoidsensor structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the quantum dot itself multi-functional by enabling it to serve both as the quantum bit carrier and as its own charge sensor through resonance oscillation. This eliminates the need for separate sensor quantum dots and reduces device complexity while maintaining or improving charge sensing capability through the resonant amplification effect.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The proposed configuration enhances sensitivity by sharply changing input and output characteristics in response to capacitance variations, enabling high-sensitivity charge detection.

Implementation Method 1

a quantum dot 1 to have a first end connected to an input terminal via a first tunnel junction and a second end connected to an output terminal via a second tunnel junction, and an inductor to be connected in parallel to the quantum dot

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a first end connected to an input terminal via a first tunnel junction and a second end connected to an output terminal via a second tunnel junction

Methodology Applied

Scientific EffectQuantum tunneling:

Implementation Method 3

it is possible to obtain an operation that the reflection amplitude, reflection phase, passing amplitude, and passing phase sharply change with respect to a change in the capacitance value of the quantum dot

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS12449461B2Charge sensor

Publication Date: 2025.10.21 MITSUBISHI ELECTRIC CORP

AI summary

A charge sensor according to the present disclosed technology includes a quantum dot to have a first end connected to an input terminal via a first tunnel junction and a second end connected to an output terminal via a second tunnel junction, and an inductor connected in parallel to the quantum dot.