Practical Non-Gaussian Detection for Enhanced Security in CV-QKD Protocols

Continuous-variable quantum key distribution (CV-QKD) has emerged as a leading protocol for unconditionally secure cryptographic key exchange, leveraging quantum properties of optical signals while remaining compatible with existing telecom infrastructure. In these systems, the receiver's detection capability directly impacts the rate at which cryptographic keys can be generated, making it a critical factor for real-time secure communications. Conventional coherent reception schemes (based solely on Gaussian operations) are fundamentally limited in their ability to distinguish quantum states, performing below the theoretical quantum limit imposed by quantum mechanics. Overcoming this limitation requires non-Gaussian detection strategies, which can approach this theoretical bound and unlock higher key generation rates. In this work, we investigate the optimized displacement receiver (ODR) - a non-Gaussian strategy that combines a signal preprocessing step with photon counting - as an alternative to conventional homodyne detection for CV-QKD protocols employing binary phase-shift keying (BPSK) modulation. We evaluate its security performance under realistic conditions by modeling practical detector imperfections such as efficiency loss and noise. Our results show that the ODR achieves higher secret key rates than conventional homodyne detection across all evaluated realistic imperfection parameters, directly translating into enhanced cryptographic security and extended transmission range.