Quantum Key Encoding with Time-Varying Pulse Profiles
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Solution Overview
Problem
Existing quantum key distribution (QKD) systems face challenges in efficiently encoding and decoding classical information into and from quantum signals, particularly in ensuring robustness against information leakage to eavesdroppers.
Innovation Solution
The proposed solution involves a method for encoding classical information into quantum signals by modulating the intensity and phase profiles of optical pulses based on time-dependent functions and encoder values, and decoding this information by measuring intensity and phase values for each pulse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional encoding methods (BB84, phase encoding, intensity encoding) are used, then the QKD system is simpler to implement, but the security against information leakage to eavesdroppers is reduced
Solution Approach 1:
The patent applies dynamics by using time-dependent intensity and phase functions to modulate optical pulses. The encoding is no longer static but varies continuously with time, creating dynamic quantum states that are more resistant to eavesdropping while maintaining implementation feasibility through programmable modulators.
Solution Approach 2:
The patent changes multiple parameters simultaneously - both intensity and phase of optical pulses are modulated according to time-dependent functions. This multi-parameter encoding approach increases security by creating more complex quantum states that are harder to distinguish, while the use of standard modulator technologies keeps the implementation complexity manageable.
2Measurement precision
If high intensity quantum states are used, then the signal-to-noise ratio is improved, but the distinguishability between states increases making them more vulnerable to eavesdropping
Solution Approach 1:
The patent simultaneously changes both intensity and phase parameters of the quantum states according to time-dependent functions. This creates a higher-dimensional encoding space where states can maintain high intensity for better signal-to-noise ratio while remaining indistinguishable to eavesdroppers who can only access limited measurement bases.
Solution Approach 2:
The patent transitions from conventional single-parameter encoding (either intensity or phase) to two-parameter encoding in the time domain. By modulating both intensity and phase with time-dependent functions, the system effectively adds another dimension to the encoding space, allowing high intensity states to remain secure.
3Reliability
If time-dependent intensity and phase modulation is applied, then the security against eavesdropping is enhanced, but the complexity of the modulation system increases
Solution Approach 1:
The patent uses dynamic time-dependent functions for both intensity and phase modulation. This approach enhances security by creating continuously varying quantum states that are harder to intercept, while the use of programmable modulators and standard optical components keeps the system complexity within practical limits.
Solution Approach 2:
The patent employs universal modulator components that can perform both intensity and phase modulation functions. By using multi-functional optical modulators and standard quantum optical components, the system achieves enhanced security through time-dependent modulation without proportionally increasing device 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
This approach enables a more robust determination of shared keys, even with increased information leakage, by employing high intensity quantum states with weak distinguishability, thereby enhancing security compared to conventional encoding methods.
Implementation Method 1
modulating an intensity profile of the optical pulse according to an intensity function which depends on a time and on a first encoder value of at least one first bit of the encoder initial bit sequence
Implementation Method 2
modulating a phase profile of the optical pulse according to a phase function which depends on a time and a second encoder value of at least one second bit of the encoder initial bit sequence
Implementation Method 3
determining an approximate intensity profile of the optical pulse by measuring a plurality of intensity values of the optical pulse for a plurality of time bins
Implementation Method 4
determining an approximate phase profile of the optical pulse by measuring a plurality of phase values of the optical pulse for a plurality of time bins
Data Source
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AI summary
The present disclosure refers to an encoding method for quantum key distribution, the method being carried out in a transmitter device (11) having a classical processor (11a) and means for preparing and transmitting quantum signals, the method comprising: generating an encoder initial bit sequence; generating, from the encoder initial bit sequence, a quantum signal comprising a plurality of optical pulses, wherein generating each optical pulse of the plurality of optical pulses comprises at least one of: modulating an intensity profile of the optical pulse according to an intensity function which depends on a time and on a first encoder value of at least one first bit of the encoder initial bit sequence; and modulating a phase profile of the optical pulse according to a phase function which depends on a time and a second encoder value of at least one second bit of the encoder initial bit sequence; transmitting the plurality of optical pulses to a receiver device (12) via a quantum channel (10a); and determining a shared key shared between the transmitter device (11) and the receiver device (12) from the encoder initial bit sequence by classical post-processing and at least one of transmitting classical information to the receiver device (12) and receiving further classical information from the receiver device (12). Further, a decoding method, a method, a transmitting device (11), a receiver device (12), and a system are disclosed.