Boosting Information Capacity

Terry Rudolph

Vikesh Siddhu

Entanglement and quantum information lie at the root of quantum theory. These remarkable resources are generally believed to diminish when systems carrying them interact with their environment. By contrast, we find that engaging a system with its environment can increases its ability to carry quantum information. The maximum rate of transmission is given by the quantum channel capacity. We counter-intuitively boost this capacity of a channel by allowing it to leak almost all quantum information to the channel's environment. We conceptually and numerically explain this boost to arise from two-letter level super-additivity in the channel's coherent information. Such super-additivity has a far larger magnitude and a qualitatively wider extent than previously known. Our findings have a surprising implication for quantum key distribution: maximum rates for key distribution can be boosted by allowing leakage of information to the eavesdropping environment.

Kamil Brádler, Esteban Castro-Ruiz, Eduardo Nahmad-Achar

In this paper we show that the quantum channel between two inertial observers who transmit quantum information by sending realistic photonic wave packets is a well-studied channel in quantum Shannon theory: the Pauli channel. The parameters of the Pauli channel and therefore its classical and quantum capacity depend on the magnitude of the Lorentz boost relating the two observers. The most striking consequence is that two inertial observers whose Pauli channel has initially zero quantum capacity can achieve nonzero quantum communication rates (reaching, in principle, its maximal value, equal to 1) by applying a boost in the right direction. This points to a fundamental connection between quantum channel capacities and special relativity.

Aman Chawla

Traditional theories of information transmission, both classical and quantum, assume that information is evaluated within a fixed and flat informational measure. Recent developments in the theory of nonlocal unification challenge this assumption by treating information as a conserved quantity whose observable manifestations depend on relational and nonlocal structure. In this paper, we develop a rigorous account of data transmission in what we term the Unified Regime, where informational observables arise as stationary quantities of a nonlocal informational action. Using Theorem A.1 of Prajnanabha, Vol. 1, Issue 1, we derive the unified (NU) entropy as a weighted logarithmic functional without assuming pointwise observer action. We show how additivity follows from the minimum interaction principle (Example 6), define unified channel capacity, and compare it with classical Shannon and quantum Holevo capacities for free-space optical (FSO) channels. The resulting framework preserves all physical channel constraints while revealing a principled capacity enhancement driven by informational geometry.

Arghavan Safavi-Naini