Encoding Multiple Qubits Boosts Quantum Communication Efficiency

A new method for entanglement-based quantum key distribution protocols sharply improves efficiency, according to Vera Uzunova and Marcin Jarzyna of the University of Warsaw. Encoding multiple qubits per photon pair optimises performance in challenging conditions, such as those expected in satellite quantum communications where signal strength is inherently low and background radiation is high. The findings reveal that optimal efficiency is achieved when a finite production probability of entangled photon pairs exists, a departure from conventional communication models. This multiqubit encoding approach can improve the secret key rate by up to an order of magnitude when compared to traditional single-qubit schemes. Optimising quantum key distribution protocols using multiqubit encoding enhances the secret key rate…