Experimental security analysis a four-photon private state

Krzysztof Dobek, Michał Karpiński, Rafał Demkowicz-Dobrzański +2 more

We report experimental generation of a noisy entangled four-photon state that exhibits a separation between secure key contents and distillable entanglement. This difference is exposed by a detailed analysis of its privacy properties.

Andrei Yu. Khrennikov

Krzysztof Dobek, Michał Karpiński, Rafał Demkowicz-Dobrzański +2 more

We report experimental generation of a noisy entangled four-photon state that exhibits a separation between the secure key contents and distillable entanglement, a hallmark feature of the recently established quantum theory of private states. The privacy analysis, based on the full tomographic reconstruction of the prepared state, is utilized in a proof-of-principle key generation. The inferiority of distillation-based strategies to extract the key is exposed by an implementation of an entanglement distillation protocol for the produced state.

Hans‐Joachim Lewerenz

Qiyu Liang, Sergio Cantu, Aditya V. Venkatramani +7 more

Mayalakshmi Kolangatt, Anirudh Verma, Sujai Matta +2 more

We theoretically propose and experimentally demonstrate the use of a configurable four-qubit photonic system to generate publicly verifiable quantum random numbers, to perform entanglement verification, and to generate a secure public and private key. Quantum circuits, to generate the desired four-qubit states and its experimental realization in the photonic architecture, are carried out using photon pairs entangled in polarization and path degrees of freedom. By performing measurements on the four-qubit system and accessing partial information of the four-qubit state for public verification, we generate publicly verified and purely secured random bits at the rate of 185 kbps from collective data of 370 kbps. When the system is used for generating public and private keys, an equal number of public and private keys are generated simultaneously. We also record about 97.9% of sampled bits from four-qubit states passing entanglement verification and demonstrate the use of public and private key generated for image encryption-decryption. The theoretical model of noise on the four-qubit state and its effect on the generation rate of verified and secured bits are in perfect agreement with the experimental results. This demonstrates the practical use of the small-scale multiqubit photonic system for quantum-safe applications by providing the option for real-time verification of the security feature of the quantum system.