Developments in scalable quantum networks rely critically on optical quantum memories, which are key components enabling the storage of quantum information. These memories play a pivotal role for entanglement distribution and long-distance quantum communication, with remarkable advances achieved in this context. However, optical memories have broader applications, and their storage and buffering capabilities can benefit a wide range of future quantum technologies. Here, we present the demonstration of a cryptography protocol incorporating an intermediate quantum memory layer. Specifically, we implement Wiesner's unforgeable quantum money primitive with a storage step, rather than as an on-the-fly procedure. This protocol imposes stringent requirements on storage efficiency and noise level to reach a secure regime. We demonstrate the implementation with polarization encoding of weak coherent states of light and a high-efficiency cold atom-based quantum memory and validate the full scheme. Our results showcase a major capability, opening broader avenues for quantum memory utilization and network functionalities.
We present FPGA-based emulation of a synchronous phase-coded quantum cryptography system. Several of the emulated subsystems are used for implementation in a free space demonstrative QPSK scheme for quantum key distribution with continuous variables (CV-QKD) using a base and optical phase synchronization. The CV-QKD systems are commonly implemented using QPSK modulation with switched or simultaneous detection. In this paper we only make use of one base of the QPSK system in order to get a simpler modulation (BPSK) scheme, used for demonstrative purposes. The reported results from the emulation and the experiment in terms of Quantum Bit Error Rate (QBER) and mutual information for different values of the number of photons per bit are in good agreement.
Quantum cryptography learning is now more important as the threats toward secure communication system using quantum computing are increasing. EDU-QCRY is one of the quantum cryptography demonstration devices which implements BB84 protocol. EDU-QCRY is still run manually that make it has limited data processing capacity, large operating time, and low-level accuracy. In this study, automation is done by parallelizing the process of selecting bases and states on the polarization rotator and integrating an Arduino-based controller module using demultiplexing techniques. EDU-QCRYI automation changes the process to be more efficient and effective because the system works automatically by a controller module based on qubit data that is inputted by the sender and the receiver gets qubit data automatically. EDU-QCRYI automation is expected to make demonstration of secure communication using Quantum cryptography more reliable for implementation.