Continuous-variable quantum key distribution (CV-QKD) over free-space channels offers more flexibility for secure key exchange between authenticated parties than fiber-based CV-QKD in practical scenarios. However, traditional CV-QKD systems use 1550-nm optical signals as the quantum source, which are susceptible to atmospheric conditions, thereby limiting their practical deployment. Additionally, the intrinsic imperfections of practical detectors result in potential security loopholes that eavesdroppers may exploit in real-world attack scenarios. To address these issues, we propose a microwave-enabled continuous-variable measurement-device-independent QKD (CV-MDI-QKD) protocol that uses microwave two-mode squeezed states generated by traveling-wave parametric amplifiers operated in a cryogenic environment as quantum sources. This enables robust free-space operation under dynamically varying atmospheric conditions and further enhances the practical security of CV-QKD systems. Numerical simulations illustrate that the proposed microwave CV-MDI-QKD system operates stably at room temperature and exhibits improved robustness against adverse weather and variations in both symmetric ($L_{\mathrm{BC}}=L_{\mathrm{AC}}$) and asymmetric ($L_{\mathrm{BC}}=0$) cases, compared to the 1550-nm scheme. The proposed microwave system exhibits a high secret key rate at suitably short distances.

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• Quantum communication
• Quantum communication, protocols & technology
• Quantum information processing
• Quantum information processing with continuous variables
• Quantum protocols