Qiang Zeng

Transmitter-device-dependence is a longstanding but often implicit problem in quantum key distribution (QKD), as compared to measurement-device-dependence. Quantum steering conceptually designates the sender and receiver in entanglement certification, offering an intuitive solution to transmitter-sided dependence. The well-known one-sided device-independent (1sDI) protocols exploit quantum steering as a resource to relax the security conditions of device-independent (DI) framework, yet provokes underlying signaling loophole. Here we formalize transmitter-device-independence based on the faithful quantum steering and propose a transmitter-device-independent (TDI) QKD protocol that closes the signaling loophole, thereby defending against common transmitter-side attacks. In a proof-of-principle experiment we validate our proposal obtaining a key-rate in the asymptotic limit of 1~kbps at a fiber transmission of 27~km. By implementing TDI security while maintaining strong loss tolerance, our approach bridges the gap between security and practicality for real-world QKD deployments.

Nonlocal correlation represents the key feature of quantum mechanics, which is exploited as a resource in quantum information processing. However, the loophole issues hamper the practical applications. We report the first demonstration of steering nonlocality with detection loophole closed at telecommunication wavelengths. In this endeavour, we design and fabricate a low-loss silicon chip for efficient entanglement generation, and further apply direct modulation technique to its optical pump to eliminate phase-encoding loss at the steering side. The newly proposed phase-encoding measurement setting adapts to an ultra fast modulation rate (GHz). Consequently, we build a fiber-optic setup that can overcome the detection efficiency that is required by quantum steering with multiple measurement settings. Our setup provides an immediate platform for exploring applications based on steering nonlocality, especially for quantum communication.

We propose and demonstrate an upgraded quantum key distribution protocol based on time-bin entanglement source with access control through introducing phase randomization. The upgraded source can protect users from memory attacks at a negligible cost.