Pulse shape optimization against Doppler shifts and delays in optical quantum communication

TL;DR

This paper investigates how pulse shape optimization can mitigate Doppler shifts and delays in space-based quantum communication, enhancing protocol robustness against synchronization errors.

Contribution

It introduces the use of the ambiguity function for pulse shape optimization to improve the resilience of CV-QKD protocols to Doppler effects in satellite links.

Findings

Gaussian pulse shapes offer better robustness than Lorentzian shapes.

Optimized pulse shapes significantly reduce performance loss due to Doppler shifts.

Pulse shape optimization can enhance the resilience of quantum networks in space environments.

Abstract

High relative velocities and large distances in space-based quantum communication with satellites in lower earth orbits can lead to significant Doppler shifts and delays of the signal impairing the achievable performance if uncorrected. We analyze the influence of systematic and stochastic Doppler shift and delay in the specific case of a continuous variable quantum key distribution (CV-QKD) protocol and identify the generalized correlation function, the ambiguity function, as a decisive measure of performance loss. Investigating the generalized correlations as well as private capacity bounds for specific choices of spectral amplitude shape (Gaussian, single- and double-sided Lorentzian), we find that this choice has a significant impact on the robustness of the quantum communication protocol to spectral and temporal synchronization errors. We conclude that optimizing the pulse shape can be a building block in the resilient design of quantum network infrastructure.