Can quantum discord increase in a quantum communication task?

Abstract

Quantum teleportation of an unknown quantum state is one of the few communication tasks which has no classical counterpart. Usually the aim of teleportation is to send an unknown quantum state to a receiver. But is it possible in some way that the receiver's state has more quantum discord than the sender's state? We look at a scenario where Alice and Bob share a pure quantum state and Alice has an unknown quantum state. She performs joint measurement on her qubits and channel to prepare Bob's qubits in a mixed state which has higher quantum discord than hers. We also observe an interesting feature in this scenario, when the quantum discord of Alice's qubits increases, then the quantum discord of Bob's prepared qubits decreases. Furthermore, we show that the fidelity of one-qubit quantum teleportation using Bob's prepared qubits as the channel is higher than using Alice's qubits.

Remote State Design for Efficient Quantum Metrology with Separable and Non-Teleporting States

“…where, { Mi } is the set of mathematical measurement operators, given as, Mi = |b i b i | ⊗ I, |b i is the ith state in the measurement basis B 1 , and I is the identity matrix of dimension 4 [24]. We calculate the quantum Fisher information of the state ρ i B .…”

“…If Alice uses B 2 as her measurement basis, the average QFI obtained by final Bob's states is greater than the QFI of the initial state for the range of values of the initial state parameter λ = 0 to λ = 0.42 (up to three decimal places). We have repeated the protocol using two other 4-qubit states as the channel shared by Alice and Bob; the 4-qubit cluster state used by Datta and Sarkar in [24], given as,…”

“…Quantum protocols like teleportation [16][17][18][19], and remote state preparation [20][21][22][23][24]] make use of entangled states shared between two spatially separated parties such as a channel, and then perform LOCC to achieve their goal. In this work, we provide a quantum protocol, where two spatially separated parties, Alice and Bob, share an entangled quantum state as 'channel', and Alice prepares a state with higher quantum Fisher information at Bob's end starting with an unknown 2-qubit single parameter Werner state [25].…”