Paul Kwiat

As the proliferation of automation in smart transportation continues, there is a need to secure communication links of “on-the-go” future mobile platforms. In this effort, we implement decoy-state quantum key distribution (QKD), which provides provably secure communication, to mobile platforms such as drones and vehicles. Unlike demonstrations in fiber of fixed point-to-point, QKD between mobile platforms provides unique challenges such as designing systems with reduced size, weight, and power, establishing a stable line-of-sight as the platforms are in motion, and maintaining performance over a wide operating temperature range, etc. We design our QKD transmitter and receiver using a modular design that is platform-agnostic. This allows us to deploy the same QKD system on an octocopter drone and a car without any hardware or software modifications. We describe critical subsystems including our resonant-cavity QKD source, custom prepare and measure optics, pointing, acquisition, and tracking system, single-photon detector, field-programmable gate array-based time-tagger, and qubit-based time-synchronization algorithm. Our achievements include drone-to-drone QKD, drone-to-car quantum transmission, and high-speed (70 mph) vehicle-to-vehicle quantum transmission on a U.S. Interstate Highway.

While most current quantum network nodes are connected via fiber-based or free-space fixed point-to-point links, there have been many advancements in the last decade that expand these nodes to include mobile, re-configurable, and wireless platforms such as uncrewed aerial vehicles (UAVs) and satellites. The size, weight, and power (SWaP) restrictions of these platforms pose constraints that potentially impact the system performance of mobile nodes. Here, we will discuss our progress towards developing a low-SWaP mobile quantum key distribution (QKD) platform that can exchange quantum-secured random keys between both drones and cars. We implement a finite-key security proof that incorporates system imperfections in state preparation and analysis, including channel losses. These imperfections, present in any system, require consideration during key consolidation to minimize information leakage. We demonstrate average finite secure key rates between mobile platforms up to 19.6 kbit/s.