Quantum Encoder with SPDC Entangled-Photon Phase Modulation
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Solution Overview
Problem
Traditional optical communications systems are susceptible to interference and eavesdropping due to weak security points, and existing quantum-based systems face challenges with qubit manipulation and high communication overhead.
Innovation Solution
A quantum encoder generates entangled photon pairs using spontaneous parametric down-conversion, encoding messages by adjusting the phase relationship between signal and idler photons, which are transmitted together to maintain the entangled state and facilitate manipulation using quantum gates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If quantum memory is used to store qubits for communication, then quantum security can be achieved, but the system becomes complex and requires high communication overhead for reconciliation
Solution Approach 1:
The patent extracts the quantum memory component from the system by using flying qubits (photons) that carry quantum information through the transmission medium directly, eliminating the need for stationary quantum memory devices while maintaining quantum security through entanglement-based protocols
Solution Approach 2:
The patent replaces the mechanical/stationary quantum memory system with an optical flying qubit system, using photons in optical fibers or free space to transmit quantum information, thereby reducing system complexity and eliminating the need for quantum memory reconciliation overhead
2Loss of information
If qubits are read to retrieve information, then information can be obtained, but the entangled state is destroyed
Solution Approach 1:
The patent performs preliminary quantum operations and encoding on the flying qubits before transmission, including preparing entangled states and applying quantum gates, so that the quantum information is already processed and encoded in a way that allows extraction without destroying the entanglement state during transmission
Solution Approach 2:
The patent uses the optical transmission medium (optical fiber or free space) as an intermediary that carries the quantum information without requiring measurement or reading during transmission, allowing the qubits to maintain their entangled state while still enabling information extraction at the destination through appropriate measurement protocols
3Device complexity
If classical encoding is used in optical communications, then the system is simple, but security is vulnerable to interference and eavesdropping
Solution Approach 1:
The patent changes the fundamental parameter of information encoding from classical to quantum, using quantum states (superposition and entanglement) of photons to encode information, which provides inherent security through quantum mechanical properties while maintaining relative system simplicity
Solution Approach 2:
The patent substitutes the classical encoding mechanism with quantum encoding using flying qubits, replacing classical signal modulation with quantum state manipulation, thereby achieving quantum security without significantly increasing system complexity
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 encoded quantum message is secure against eavesdropping, as tampering destroys the entangled state, and the system does not require quantum memory or repeaters, offering enhanced security and efficiency.
Implementation Method 1
a spontaneous parametric down-conversion (SPDC) device receives the source photons and produces therefrom entangled photon pairs
Implementation Method 2
A phase encoder is disposed in the signal or idler path and operable to alter the phase of the signal photon stream. An encoding signal source is coupled to the phase encoder to supply an encoding signal, causing the phase encoder to alter the differential phase relationship of the signal and idler photons
Data Source
AI summary
A stream of photons from an optical source at a source wavelength are converted into entangled photon pairs via a spontaneous parametric down-conversion process. This produces time-synchronized signal and idler photon pairs which share a nominal wavelength, twice the source wavelength, a common polarization. The signal and idler individually have wavelengths that are equally offset above and below their nominal wavelength. The photons segregated into two paths based on wavelength via a wavelength division multiplexer. A phase modulator in the signal path alters the phase of the signal photon, while the idler photon's phase remains unchanged. By applying a modulation signal to the phase modulator, a quantum message is encoded on the photon pair. A multi-channel wavelength division multiplexer may be used to support multiple channels, each carrying signal-idler pairs conveying a quantum encoded message.