Rate Meter Circuit for Phase-Sensitive Single-Photon Detection

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Solution Overview

Problem

Conventional lock-in amplifiers are inadequate for processing discrete voltage pulses from single-photon detectors, as they require wide bandwidths, leading to reduced signal-to-noise ratios and difficulties in implementing phase-sensitive detection and real-time control for applications like magnetometry using nitrogen-vacancy centers in diamond.

Innovation Solution

A rate meter that transforms discrete voltage pulses into a phase-sensitive continuous signal by directing the pulses between processing channels based on a modulation signal, determining rate voltages, processing these with low-pass filters, and outputting a normalized differential output, enabling real-time magnetometry and control without the need for computer processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional lock-in amplifiers are used to process discrete voltage pulses, then phase-sensitive detection can be performed, but the signal-to-noise ratio is reduced due to the wide bandwidth required for discrete signals

Engineering Contradiction:

Improvephase-sensitive detection capabilityVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary device (the rate meter circuit) between the single-photon detector and the lock-in amplifier. This intermediary transforms the discrete voltage pulses into a continuous voltage signal that is proportional to the pulse rate, making the signal compatible with lock-in amplifier processing while maintaining phase-sensitive detection capability and improving signal-to-noise ratio.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If discrete voltage pulses are processed directly by lock-in amplifiers, then measurement can be performed, but the bandwidth must be wide which reduces signal-to-noise ratio

Engineering Contradiction:

Improvemeasurement capabilityVSAvoidsignal-to-noise ratio

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the parameter of the signal from discrete pulses to continuous voltage by transforming the pulse train into a continuous signal whose amplitude represents the pulse rate. This parameter transformation allows the use of narrow bandwidth lock-in amplifier processing while maintaining measurement capability and improving signal-to-noise ratio.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If single-photon detectors are used for high spatial resolution, then detection sensitivity is improved, but the output signal power is too low for regular photo-detectors

Engineering Contradiction:

Improvespatial resolutionVSAvoidsignal power

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces the conventional photo-detector system with a single-photon detector system that uses electronic pulse processing instead of direct optical power detection. By substituting the detection mechanism from measuring optical power to counting individual photons and converting to a continuous rate signal, the system achieves high spatial resolution while generating sufficient electrical signal power for further processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Measurement precision

If pulse counting with computer post-processing is used, then discrete signals can be processed, but real-time control and stabilization are difficult to implement

Engineering Contradiction:

Improvepulse detection accuracyVSAvoidreal-time control capability

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent creates a continuous voltage output signal that continuously represents the pulse rate, enabling real-time control and stabilization operations. This continuous signal allows feedback control systems to operate in real-time without the delays and discretization issues of computer-based post-processing, while maintaining accurate pulse detection capability.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS10999109B2Device and method to transform discrete voltage pulses to a phase-sensitive continuous signal

Publication Date: 2021.05.04 THE GOVERNMENT OF THE UNITED STATES OF AMERICA AS REPRESENTED BY THE SECRETARY DEPARTMENT OF HEALTH & HUMAN SERVICES

AI summary

Systems, methods, and apparatuses, for transform discrete voltage pulses to a continuous signal. One method may include receiving a pulsed-voltage signal. The method may also include alternately directing the pulsed-voltage signal between a pair of processing channels based on a modulation signal or another signal. The method may further include determining rate voltages corresponding to the pair of processing channels based on a pulse rate of the pulsed-voltage signal. Further, the method may include processing the rate voltages using low pass filters corresponding to the pair of processing channels to form filtered rate voltages. The method may also include determining a normalized differential output for the pair of processing channels based on the filtered rate voltages. The method may also include outputting the normalized differential output to an output connector.