Single-Electron Thermometer Using Coulomb Blockade
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Solution Overview
Problem
Current thermometers, especially outside standard laboratories, are often secondary and require calibration, which can be complex and prone to drift, and they may not be fast or compact enough for various applications, particularly at low temperatures.
Innovation Solution
A primary electronic thermometer using a single-electron device, such as a single-electron box or transistor, with a quantum dot and a charge reservoir, measures temperature by varying the gate voltage to determine the full width half maximum of the differential capacitance or phase shift, allowing direct temperature conversion without the need for calibration or drift compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If secondary thermometers are used, then calibration is required, but this introduces complexity and potential drift
Solution Approach 1:
The thermometer uses the Johnson noise of its own resistor to measure temperature, making the measurement system self-calibrating and eliminating the need for external calibration references. The resistor's thermal noise provides a direct, intrinsic temperature signal that requires no prior calibration.
Solution Approach 2:
The patent replaces mechanical or chemical calibration methods with an electronic approach using Johnson noise measurement. By measuring the thermal noise voltage spectrum of a resistor, the system directly determines temperature through the Johnson-Nyquist formula, eliminating mechanical calibration procedures.
2Speed
If traditional thermometers are used, then measurement speed is limited, but fast measurement requires sophisticated equipment
Solution Approach 1:
The patent replaces slow thermal conduction-based measurement with electronic noise measurement. By measuring the voltage noise spectrum across a resistor, the system can determine temperature extremely rapidly, limited only by the electrical measurement bandwidth rather than thermal response time.
Solution Approach 2:
The patent measures temperature by analyzing the frequency spectrum of voltage noise across a resistor. By changing the measurement parameter from thermal conduction rate to electrical noise spectral density, the system achieves much faster response times while maintaining measurement accuracy.
3Volume of moving object
If compact thermometers are used, then device size is reduced, but measurement accuracy may be compromised
Solution Approach 1:
The patent replaces bulk thermal sensing with electronic noise measurement at the circuit level. By measuring Johnson noise voltage directly across a small resistor, the system achieves accurate temperature measurement in a compact form factor without requiring large thermal mass or complex thermal coupling structures.
4Reliability
If thermometers independent of magnetic fields are used, then measurement stability is improved, but such thermometers are rare
Solution Approach 1:
The patent replaces magnetic field-dependent effects with electronic noise measurement. By measuring Johnson noise voltage, the system is inherently immune to magnetic field interference since the measurement relies on thermal electrical noise rather than magnetic properties of materials.
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 solution provides a simple, fast, and accurate temperature measurement from milli-Kelvin to several tens of Kelvin, independent of external magnetic fields, eliminating the need for calibration and enabling quick temperature readings in a sub-microsecond range.
Implementation Method 1
The single-electron device, which may be a single-electron box or a single-electron transistor, comprises a quantum dot, a charge reservoir coupled to the quantum dot via a tunnel barrier and a gate electrode capacitively coupled to the quantum dot, the single-electron device capable of exhibiting Coloumb blockade
Implementation Method 2
measuring corresponding values of a voltage-dependent term of differential capacitance of the quantum dot and the reservoir as seem from the gate (or 'gate differential capacitance of the quantum dot-reservoir system')
Implementation Method 3
converting the full width half maximum value into a temperature
Implementation Method 4
measuring a phase shift of a reflected signal obtained using reflectometry
Data Source
Figure 1~2(d)
Figure 3
Figure 4(a)~5
AI summary
A method of measuring temperature using a single-electron device (1) is described. The single-electron device (1), which may be a single-electron box or a single-electron transistor, comprises a quantum dot (2), a charge reservoir (3) coupled to the quantum dot via a tunnel barrier (4) and a gate (5) capacitively coupled to the quantum dot, the single-electron device capable of exhibiting Coloumb blockade. The method comprises varying a gate voltage applied to the gate around a given gate voltage at which electrochemical level of the quantum dot and electrochemical level of the reservoir are equal and measuring corresponding values of a voltage-dependent term of differential capacitance of the quantum dot and the reservoir as seen from the gate or of values of a property dependent thereon (such as phase shift of a reflected signal obtained using reflectometry), measuring a full width half maximum value of the voltage-dependent term of the differential capacitance or the property as a function of gate voltage, and converting the full width half maximum value into a temperature.