68 research outputs found
Probabilistic coding of quantum states
We discuss properties of probabilistic coding of two qubits to one qutrit and
generalize the scheme to higher dimensions. We show that the protocol
preservers entanglement between qubits to be encoded and environment and can be
also applied to mixed states. We present the protocol which enables encoding of
n qudits to one qudit of dimension smaller than the Hilbert space of the
original system and then probabilistically but error-free decode any subset of
k qudits. We give a formula for the probability of successful decoding
Entanglement-swapping boxes and their communication properties
We pose the fundamental question of communication properties of primitives
irrespectively of their implementation. To illustrate the idea we introduce the
concept of entanglement-swapping boxes, i.e. we consider any quantum operations
which perform entanglement swapping, not necessarily via simple quantum
teleportation. We ask a question about the properties of such boxes., i.e. what
local operations and how much classical communication are needed to perform
them. We also ask if any box which performs entanglement swapping can be used
to establish classical communication. We show that each box needs at least two
bits of classical communication to perform it. It is also shown that each box
can be used for classical communication and, most importantly, that there exist
boxes which allow to communicate at most one bit. Surprisingly we find basic
irreversibility in the process of entanglement swapping with respect to its
communication properties.Comment: Accepted for publication in Phys. Rev. A as a Rapid Communicatio
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