Summary form only given. Entanglement is the resource that makes quantum communication and quantum computation work. The most basic quantum communication protocols are quantum cryptography, quantum teleportation and entanglement swapping. In quantum teleportation one of two parties wants to send the other one a quantum state using some independent carrier. Entanglement swapping in its simplest form is the use of quantum teleportation to transmit a quantum state that is already entangled with some other state. Thereby the entanglement that existed between the original particle and its partner is transferred to the output particle. Both teleportation and entanglement swapping have successfully been demonstrated. However, in none of the experiments the quality of teleportation was high enough to produce output correlations that could have violated a Bell-type inequality. In this work we will show that qubit teleportation using polarization-entangled photon pairs can produce the desired correlations.
Summary form only given. Entanglement is the resource that makes quantum communication and quantum computation work. The most basic quantum communication protocols are quantum cryptography, quantum teleportation and entanglement swapping. In quantum teleportation one of two parties wants to send the other one a quantum state using some independent carrier. Entanglement swapping in its simplest form is the use of quantum teleportation to transmit a quantum state that is already entangled with some other state. Thereby the entanglement that existed between the original particle and its partner is transferred to the output particle. Both teleportation and entanglement swapping have successfully been demonstrated. However, in none of the experiments the quality of teleportation was high enough to produce output correlations that could have violated a Bell-type inequality. In this work we will show that qubit teleportation using polarization-entangled photon pairs can produce the desired correlations.
Quantum teleportation is one of the essential primitives of quantum communication. We suggest that any quantum teleportation scheme can be characterized by its efficiency, i.e. how often it succeeds to teleport, its fidelity, i.e. how well the input state is reproduced at the output, and by its insensitivity to cross talk, i.e. how well it rejects an input state that is not intended to teleport. We discuss these criteria for the two teleportation experiments of independent qubits which have been performed thus far. In the first experiment (Nature 390,575 (1997)) where the qubit states were various different polarization states of photons, the fidelity of teleportation was as high as 0.80 ± 0.05 thus clearly surpassing the limit of 2/3 which can, in principle, be obtained by a direct measurement on the qubit and classical communication. This high fidelity is confirmed in our second experiment (Phys. Rev. Lett. 80, 3891 (1998)), demonstrating entanglement swapping, that is, realizing the teleportation of a qubit which itself is still entangled to another one. This experiment is the only one up to date that demonstrates the teleportation of a genuine unknown quantum state. 1
Quantum teleportation is one of the essential primitives of quantum communication. We suggest that any quantum teleportation scheme can be characterized by its efficiency, i.e. how often it succeeds to teleport, its fidelity, i.e. how well the input state is reproduced at the output, and by its insensitivity to cross talk, i.e. how well it rejects an input state that is not intended to teleport. We discuss these criteria for the two teleportation experiments of independent qubits which have been performed thus far. In the first experiment (1997, Nature, 390, 575) where the qubit states were various different polarization states of photons, the fidelity of teleportation was as high as 0.80 ± 0.05 thus clearly surpassing the limit of 2/3 which can, in principle, be obtained by a direct measurement on the qubit and classical communication. This high fidelity is confirmed in our second experiment (1998, Phys. Rev. Lett., 80, 3891), demonstrating entanglement swapping, that is, realizing the teleportation of a qubit which itself is still entangled to another one. This experiment is the only one to date that demonstrates the teleportation of a genuine unknown quantum state.
Quantum teleportation is one of the essential primitives of quantum communication. We suggest that any quantum teleportation scheme can be characterized by its efficiency, i.e. how often it succeeds to teleport, its fidelity, i.e. how well the input state is reproduced at the output, and by its insensitivity to cross talk, i.e. how well it rejects an input state that is not intended to teleport. We discuss these criteria for the two teleportation experiments of independent qubits which have been performed thus far. In the first experiment (1997, Nature, 390, 575) where the qubit states were various different polarization states of photons, the fidelity of teleportation was as high as 0.80 ± 0.05 thus clearly surpassing the limit of 2/3 which can, in principle, be obtained by a direct measurement on the qubit and classical communication. This high fidelity is confirmed in our second experiment (1998, Phys. Rev. Lett., 80, 3891), demonstrating entanglement swapping, that is, realizing the teleportation of a qubit which itself is still entangled to another one. This experiment is the only one to date that demonstrates the teleportation of a genuine unknown quantum state.
Abstract Chapter 14 discusses the quantum communication protocol called quantum teleportation, which uses the quantum correlations in an entangled particle pair shared between two observers to transmit the information stored in the (unknown) quantum state of a target system from one of the observers to the other. After reviewing the theoretical basics we showcase some of the important experimental demonstrations of teleportation. We then turn to more general protocols related to teleportation such as entanglement swapping, and the general formalism of isometries, before inspecting the option of delayed-choice entanglement swapping. In the light of these findings we compare teleportation to classical information transfer and inspect the related dense-coding protocol. Finally, we give an overview of basic quantum key distribution protocols is given, including the Bennett-Brassard-84 protocol based on conjugate coding and the entanglement-based Ekert-91 protocol
Quantum teleportation strikingly underlines the peculiar features of the quantum world. We present an experimental proof of its quantum nature, teleporting an entangled photon with such high quality that the nonlocal quantum correlations with its original partner photon are preserved. This procedure is also known as entanglement swapping. The nonlocality is confirmed by observing a violation of Bell's inequality by 4.5 standard deviations. Thus, by demonstrating quantum nonlocality for photons that never interacted, our results directly confirm the quantum nature of teleportation.
Protocols for probabilistic entanglement-assisted quantum teleportation and for entanglement swapping of material qubits are presented. They are based on a protocol for postselective Bell- state projection which is capable of projecting two material qubits onto a Bell state with the help of ancillary coherent multiphoton states and postselection by balanced homodyne photodetection. Provided this photonic postselection is successful, we explore the theoretical possibilities of realizing unit-fidelity quantum teleportation and entanglement swapping with 25 success probability. This photon-assisted Bell projection is generated by coupling almost resonantly the two material qubits to single modes of the radiation field in two separate cavities in a Ramsey-type interaction sequence and by measuring the emerged field states in a balanced homodyne detection scenario. As these quantum protocols require basic tools of quantum state engineering of coherent multiphoton states and balanced homodyne photodetection, they may offer interesting perspectives in particular for current quantum optical applications in quantum information processing.