Capacity of trace decreasing quantum operations and superadditivity of coherent information for a generalized erasure channel

Abstract

Losses in quantum communication lines severely affect the rates of reliable information transmission and are usually considered to be state-independent. However, the loss probability does depend on the system state in general, with the polarization dependent losses being a prominent example. Here we analyze biased trace decreasing quantum operations that assign different loss probabilities to states and introduce the concept of a generalized erasure channel. We find lower and upper bounds for the classical and quantum capacities of the generalized erasure channel as well as characterize its degradability and antidegradability. We reveal superadditivity of coherent information in the case of the polarization dependent losses, with the difference between the two-letter quantum capacity and the single-letter quantum capacity exceeding $7.197\cdot 10^{-3}$ bit per qubit sent, the greatest value among qubit-input channels reported so far.

arXiv comment16 pages, 5 figures

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Cited by in corpus (10)

• Riemannian geometry and automatic differentiation for optimization problems of quantum physics and quantum technologies
• Generic nonadditivity of quantum capacity in simple channels
• Entropic singularities give rise to quantum transmission
• Exploring super-additivity of coherent information of noisy quantum channels through Genetic algorithms
• Trace decreasing quantum dynamical maps: Divisibility and entanglement dynamics
• Multipartite entanglement to boost superadditivity of coherent information in quantum communication lines with polarization dependent losses
• Postselected communication over quantum channels
• The superadditivity effects of quantum capacity decrease with the dimension for qudit depolarizing channels
• Conditional Action and imperfect Erasure of Qubits
• Additivity of quantum capacities in simple non-degradable quantum channels