PLC Time-Phase Decoder for Compact Stable QKD Receivers
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Solution Overview
Problem
Existing quantum key distribution (QKD) decoders suffer from size and performance trade-offs due to silicon-based chips requiring external polarization controllers and optical circulators, leading to high optical coupling losses and instability.
Innovation Solution
Implementing a miniaturized time phase decoder and QKD receiver using a planar lightwave circuit (PLC) chip, integrating all devices on-chip with controlled interferometer arm lengths and passive components, eliminating the need for external polarization controllers and phase modulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional optical components and electronic circuits are miniaturized for portable QKD devices, then device portability is improved, but measurement precision and reliability deteriorate due to increased component losses and reduced performance
Solution Approach 1:
The patent replaces conventional electronic time-to-digital converters and signal processing circuits with a purely optical time phase decoding mechanism. The optical signal directly encodes time phase information through interference patterns, eliminating the need for electronic conversion and associated losses. This substitution maintains measurement precision while enabling miniaturization, as optical components can be integrated at smaller scales without the same performance degradation as electronic components.
2Device complexity
If miniaturized optical components are used, then device complexity is reduced, but loss of information increases due to component losses in compact configurations
Solution Approach 1:
The patent implements a nested optical cavity structure where resonators are integrated within compact volumes. The optical signals are confined and circulated through these nested structures, allowing multiple optical paths and processing functions to be packed into a small footprint. This nesting approach reduces device complexity and size while maintaining signal integrity by keeping optical paths contained and minimizing coupling losses between components.
Solution Approach 2:
The patent performs preliminary optical signal processing within the compact device, including time phase encoding and interference pattern generation, before the signal exits the miniaturized system. By completing critical signal processing functions within the optical domain while the signal is still in the system, the patent eliminates the need for additional external components that would increase complexity and introduce further losses.
3Measurement precision
If conventional time-to-digital conversion methods are used, then measurement capability is achieved, but device portability is compromised due to bulky electronic circuits
Solution Approach 1:
The patent replaces electronic time-to-digital conversion with direct optical time phase measurement. The optical signal's phase directly encodes temporal information, and this phase information is read out optically through interference measurements. This eliminates bulky electronic conversion circuits while maintaining measurement capability, as the optical domain naturally preserves time phase information without requiring electronic sampling and digitization hardware.
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
Achieves reduced system size and improved performance by ensuring stable interference and balanced detection signals without external devices, enhancing key rate stability and reliability.
Implementation Method 1
a first optical signal and a second optical signal are received, wherein the first optical signal and the second optical signal are interfered to generate an interference signal
Data Source
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AI summary
Disclosed in the present invention are a miniaturized time phase decoder based on a planar optical waveguide chip and a QKD receiver. All on-chip devices are manufactured on the basis of a PLC process, an arm length difference of an interferometer can be accurately controlled by means of an existing process, and interference stability maintenance does not need to be carried out on devices such as a phase shifter or a phase modulator built in an interference ring; except an external single-photon detector, all functional devices are passive devices and have relatively high stability and reliability; moreover, because a PLC planar optical waveguide mode can be basically consistent with a mode in an optical fiber, the polarization state does not need to be specially controlled before coupling into a chip, the requirements on devices such as an external polarization controller are reduced, and the size of a QKD receiver is further reduced.