Curator's Take
This fascinating theoretical work bridges two fundamental quantum concepts by showing that the quantum advantage in Random Access Code protocols can be achieved using entanglement within a single particle rather than between separate particles, while establishing a direct quantitative link between this advantage and quantum contextuality. The researchers demonstrate that the degree of quantum contextuality violation in single-particle measurements directly corresponds to the enhancement in success probability for these information encoding protocols. This connection is particularly significant because it provides a concrete way to measure and understand the quantum resources responsible for computational advantages, potentially opening new pathways for quantum sensing applications that exploit intraparticle entanglement. The work offers both theoretical insights into the nature of quantum advantage and practical implications for designing more efficient quantum protocols using single-particle systems.
— Mark Eatherly
Summary
The quantum enhancement of success probability in the Random Access Code (RAC) protocols remains unexplored from two important perspectives. First, the use of entanglement between two co-measurable degrees of freedom of a single particle (intraparticle entanglement) in achieving such quantum enhancement has not been investigated. Second, no explicit quantitative correspondence has been established between the predicted/observed quantum advantage and the underlying quantum resource responsible for it. In this work, we address both these aspects simultaneously by harnessing a single-particle resource. For this purpose, the RAC protocol is formulated in terms of intraparticle entanglement between, for instance, spin/polarization and path degrees of freedom of a single particle. Within this framework, a relevant Bell-type inequality, derived from the assumption of noncontextuality for single particle path-spin measurements, is used. Based on these ingredients, the formulated analysis reveals that the magnitude of quantum-mechanical violation of such Bell-type inequality, signifying a form of quantum contextuality, is quantitatively commensurate with the quantum enhancement of success probability in any intraparticle entanglement-assisted $n$-bit RAC protocol. In particular, the maximal success probability of a quantum $n \mapsto 1$ RAC protocol corresponds to the maximal quantum violation of the relevant Bell-type inequality. This correspondence is empirically testable using a readily implementable single-particle interferometric setup requiring coherence preservation only for a single particle.