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Iulia Ghiu

Publications and source records attributed to Iulia Ghiu.

25 records · Page 2Linked to original sources
arXiv2010

Probing light polarization with the quantum Chernoff bound

We recall the framework of a consistent quantum description of polarization of light. Accordingly, the degree of polarization of a two-mode state $\hat ρ$ of the quantum radiation field can be defined as a distance of a related state ${\hat ρ}_b$ to the convex set of all SU(2) invariant two-mode states. We explore a distance-type polarization measure in terms of the quantum Chernoff bound and derive its explicit expression. A comparison between the Chernoff and Bures degrees of polarization leads to interesting conclusions for some particular states chosen as illustrative examples.

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arXiv2009

Quantum Chernoff bound as a measure of nonclassicality for one-mode Gaussian states

We evaluate a Gaussian distance-type degree of nonclassicality for a single-mode Gaussian state of the quantum radiation field by use of the recently discovered quantum Chernoff bound. The general properties of the quantum Chernoff overlap and its relation to the Uhlmann fidelity are interestingly illustrated by our approach.

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arXiv2009

Local transformations of superpositions of entangled states

Suppose that we have two entangled states $\ket {ϕ_1}$, $\ket{ψ_1}$ that cannot be converted to any of other two states $\ket{ϕ_2}$, $\ket{ψ_2}$ by local operations and classical communication. We analyze the possibility of locally transforming a superposition of $\ket{ϕ_1}$ and $\ket{ψ_1}$ into a superposition of $\ket{ϕ_2}$ and $\ket{ψ_2}$. By using the Nielsen's theorem we find the necessary and sufficient conditions for this conversion to be performed.

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arXiv2006

Asymmetric two-output quantum processor in any dimension

We propose two different implementations of an asymmetric two-output probabilistic quantum processor, which can implement a restricted set of one-qubit operations. One of them is constructed by combining asymmetric telecloning with a quantum gate array. We analyze the efficiency of this processor by evaluating the fidelities between the desired operation and the one generated by the processor and show that the two output states are the same as the ones produced by the optimal universal asymmetric Pauli cloning machine. The schemes require only local operations and classical communication, they have the advantage of transmitting the two output states directly to two spatially separated receivers but they have a success probability of 1/2. We show further that we can perform the same one-qubit operation with unity probability at the cost of using nonlocal operations. We finally generalize the two schemes for D-level systems and find that the local ones are successful with a probability of 1/D and the nonlocal generalized scheme is always successful.

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arXiv2005

Broadcasting of entanglement at a distance using linear optics and telecloning of entanglement

We propose a scheme for broadcasting entanglement at a distance based on linear optics. We show that an initial polarization entangled state can be simultaneously split and transmitted to a pair of observers situated at different locations with the help of two conditional Bell-state analyzers based on two beam splitters characterized by the same reflectivity R. In particular for R=1/3 the final states coincide with the output states obtained by the broadcasting protocol proposed by Buzek et al. [Phys. Rev. A 55, 3327 (1997)]. Further we present a different protocol called telecloning of entanglement, which combines the many-to-many teleportation and nonlocal optimal asymmetric cloning of an arbitrary entangled state. This scheme allows the optimal transmission of the two nonlocal optimal clones of an entangled state to two pairs of spatially separated receivers.

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arXiv2003

Asymmetric quantum telecloning of d-level systems and broadcasting of entanglement to different locations using the "many-to-many" communication protocol

We propose a generalization of quantum teleportation: the so-called many-to-many quantum communication of the information of a d-level system from N spatially separated senders to M>N receivers situated at different locations. We extend the concept of asymmetric telecloning from qubits to d-dimensional systems. We investigate the broadcasting of entanglement by using local 1->2 optimal universal asymmetric Pauli machines and show that the maximal fidelities of the two final entangled states are obtained when symmetric machines are applied. Cloning of entanglement is studied using a nonlocal optimal universal asymmetric cloning machine and we show that the symmetric machine optimally copies the entanglement. The "many-to-many" teleportation scheme is applied in order to distribute entanglement shared between two observers to two pairs of spatially separated observers.

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