Entangled Photon Source Alignment via Pump Beam Feedback
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Solution Overview
Problem
Existing methods for aligning and stabilizing entangled photon sources, particularly in free-space sources, suffer from the need for manual adjustments due to optical component drifts, which disrupt the generation of entangled photons and quantum key distribution.
Innovation Solution
An automated alignment and stabilization method and system using a control loop that adjusts the spatial mode of the pump beam by measuring and filtering it after entangled photon generation, employing spatial mode filters, detection means, and control signals to align and stabilize the pump beam through non-linear elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If manual alignment of optical components is performed periodically to counteract drifts, then alignment stability is improved, but system downtime and loss of entangled photon generation occur
Solution Approach 1:
The patent implements a feedback control system where the spatial mode of the pump beam is continuously monitored after entangled photon generation, and alignment means are automatically adjusted based on the detected deviations. This closed-loop feedback mechanism maintains alignment stability without requiring manual intervention or system shutdown.
Solution Approach 2:
The system performs self-alignment by automatically detecting spatial mode deviations and adjusting its own optical components through actuation means. The entangled photon source system corrects its own alignment drifts without external manual intervention, eliminating the need for periodic manual realignment and associated downtime.
2Reliability
If the pump beam spatial mode is not stabilized, then entangled photon quality deteriorates over time, but automated alignment systems increase device complexity
Solution Approach 1:
The spatial mode filter serves multiple functions: it filters the pump beam spatial mode, provides a reference for detection, and enables feedback control. This multi-functional approach maintains entangled photon quality without requiring separate dedicated components for each function, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent introduces a spatial mode filter as an intermediary element that mediates between the pump beam and the detection system. This intermediary provides a simplified interface for measuring spatial mode deviations and enables automatic control without requiring complex direct measurement systems.
3Manufacturing precision
If manual realignment is performed to maintain pump beam spatial mode, then alignment precision is restored, but entangled photon generation is interrupted
Solution Approach 1:
The patent implements continuous monitoring and continuous adjustment of the pump beam spatial mode through automated feedback control. The useful action of entangled photon generation continues uninterrupted while the system continuously corrects alignment deviations, eliminating the stop-start nature of manual realignment procedures.
Solution Approach 2:
The patent replaces manual mechanical alignment procedures with an automated optical feedback system. Instead of physically manipulating optical components by hand, the system uses optical detection of spatial mode deviations and automated actuation, enabling precision maintenance without interrupting photon generation.
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 ensures stable entangled photon generation with consistent quality by continuously monitoring and adjusting the pump beam, eliminating the need for interrupting photon generation for maintenance, thus maintaining alignment and stabilization without disrupting the entangled photon process.
Implementation Method 1
the most efficient method of preparing entangled photons is via spontaneous parametric down-conversion (SPDC) which occurs in highly birefringent non-linear crystals arranged in a source
Implementation Method 2
measurement of the pump beam after the generation of the entangled photons by spatial mode filtering of the pump beam by a spatial mode filter means
Data Source
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AI summary
It is claimed a method for alignment and/or stabilization of an entangled photon source (2) with the steps, i) generation of a polarized pump beam (10) by a pump laser (1); ii) generation of entangled photons (20) by guidance of the pump beam (10) to a non-linear element (21) in the source (2) via one or more alignment means. According to the invention the method comprises the steps iii) measurement of the pump beam (10) after the generation of the entangled photons (20) by spatial mode filtering of the pump beam (10) and detection of the spatial mode filtered pump beam (11) after the generation of the entangled photons (20); iv) generation of a control signal (12) based on the spatial mode filtered pump beam (11) in a control means (5); v) adjustment of the one or more alignment means by the control signal (12) in order to align and/or stabilize the spatial mode of the pump beam (10) in the source (2).