Continuous Variable Teleportation with Non-Gaussian Resources in the Characteristic Function

Fabio Dell’Anno, Silvio De Siena, L. Albano Farias +1 more

Ankita, Arpita Chatterjee

L. Albano Farias

A characteristic function (CF) based formalism for the representation of quantum optical operations pertaining to the Continuous Variable (CV) quantum teleportation protocol for general resource and input states is introduced; allowing for modifications of basic CV teleportation; such as lossy homodyne measurements and the presence of thermal noise. The output state CF is given as a product of the CFs of resource and input. The use of non-Gaussian resources is studied by means of a general class of two-mode squeezed Bell-like states that include as special cases Gaussian, non-Gaussian and "degaussified" resources; it is shown that Bell-like resources optimized ("tailored") for maximum fidelity yield a remarkable improvement in fidelity of teleportation for the studied input states. A further generalization is introduced with two-mode squeezed superpositions of Fock states including finite truncations of Gaussian states as special cases; it is shown that the optimization for maximum fidelity reduces these resources to truncated Gaussian states. Another class of non-Gaussian resources is introduced, optimized squeezed cat-like states; their performance is shown to be higher than that of a Gaussian state; but lower than that for the Bell-like states. It is shown that the optimal non-Gaussian resources are those that most closely realize the simultaneous maximization of the entanglement, the affinity with the two-mode squeezed vacuum and the (suitably measured) amount of non-Gaussianity. The teleportation of coherent state inputs is studied using squeezed Bell-like and squeezed cat-like states superimposed over Gaussian modes representing thermal noise; it is shown that the optimized non-Gaussian resources are more robust in the presence of noise then Gaussian resources.

Fabio Dell’Anno, Silvio De Siena, Fabrizio Illuminati

We present a comprehensive investigation of nonideal continuous-variable quantum teleportation implemented with entangled non-Gaussian resources. We discuss in a unified framework the main decoherence mechanisms, including imperfect Bell measurements and propagation of optical fields in lossy fibers, applying the formalism of the characteristic function. By exploiting appropriate displacement strategies, we compute analytically the success probability of teleportation for input coherent states and two classes of non-Gaussian entangled resources: two-mode squeezed Bell-like states (that include as particular cases photon-added and photon-subtracted de-Gaussified states), and two-mode squeezed catlike states. We discuss the optimization procedure on the free parameters of the non-Gaussian resources at fixed values of the squeezing and of the experimental quantities determining the inefficiencies of the nonideal protocol. It is found that non-Gaussian resources enhance significantly the efficiency of teleportation and are more robust against decoherence than the corresponding Gaussian ones. Partial information on the alphabet of input states allows further significant improvement in the performance of the nonideal teleportation protocol.

秦涛, 赵梅生, 张永德

Chandan Kumar, Shikhar Arora

Non-Gaussian operations have been shown to enhance the fidelity of continuous-variable quantum teleportation. However, a disadvantage of these non-Gaussian operations is that they are probabilistic in nature. In this article we study the trade-off between teleportation fidelity and success probability for optimal performance of the teleportation protocol. To this end, we first derive a unified expression for the Wigner characteristic function describing three non-Gaussian states: photon-subtracted, photon-added, and photon-catalyzed two-mode squeezed vacuum states. We then utilize it to obtain the fidelity of teleportation for input coherent and squeezed vacuum states using the aforementioned non-Gaussian resource states. We optimize the product of the relative enhancement in fidelity and the probability of state preparation by tuning the transmissivity of the beam splitters involved in implementing non-Gaussian operations. This leads to a scenario that can be effectively implemented in a laboratory to enhance fidelity. It turns out that among all the non-Gaussian resource states considered, the symmetric one-photon-subtracted two-mode squeezed vacuum state is the most advantageous. We provide the associated optimal squeezing and beam splitter transmissivity values for the non-Gaussian resource states considered, which will be of significant interest to the experimental community. We also consider the effect of imperfect photon detectors on teleportation fidelity. Further, we expect the derived Wigner characteristic function to be useful in state characterization and other quantum information processing protocols.