Experimental realization of freely propagating teleported qubits

Abstract

Quantum teleportation is central to quantum communication, and plays an important role in a number of quantum computation protocols. Most information-processing applications of quantum teleportation include the subsequent manipulation of the qubit (the teleported photon), so it is highly desirable to have a teleportation procedure resulting in high-quality, freely flying qubits. In our previous teleportation experiment, the teleported qubit had to be detected (and thus destroyed) to verify the success of the procedure. Here we report a teleportation experiment that results in freely propagating individual qubits. The basic idea is to suppress unwanted coincidence detection events by providing the photon to be teleported much less frequently than the auxiliary entangled pair. Therefore, a case of successful teleportation can be identified with high probability without the need actually to detect the teleported photon. The experimental fidelity of our procedure surpasses the theoretical limit required for the implementation of quantum repeaters.

Quantum optical systems for the implementation of quantum information processing

“…Then, even under perfect conditions of zero loss, a three-fold coincidence on Alice's side of the experiment does not guarantee a photon is sent to Bob. In a later manifestation of the experiment the possibility of such errors was made negligible and fidelities of > 80% were observed, well in excess of the 2/3 limit [98].…”

Requirement for quantum computation

“…Optical realizations of quantum information processing benefit from advanced techniques in quantum optics for state preparation, unitary evolution with low decoherence and high-efficiency measurement. Both qubit [6,7,8] and continuous-variable [9,10] schemes allow optical quantum information processing; experiments demonstrating optical quantum teleportation [11,12,13] and proposals for schemes such as optical quantum secret sharing [14,15] are testimony to advances in quantum optical quantum information tasks and processes.…”

“…Such squeezed states, however, are still Gaussian and fall within the constraints of our theorem. Thus, although techniques of linear optics and squeezing with semiclassical sources and homodyne detection are highly advanced and can demonstrate non-classical properties such as quantum teleportation [11,12,13] and quantum secret sharing [14,15], they are insufficient to perform proper quantum computation.…”

Limitations on building single-photon-resolution detection devices

“…As a consequence, postselection was needed. Recently, Pan et al modified the pair-production rates of the two down-converters in this experiment, such that the nonpostselected output fidelity surpasses the classical limit [13].However, it may not always be possible to modify the quantum gate in such a way that non-SPR detectors can be used, and we really would like to have cheap, reliable, and efficient SPR detection devices. But the current experimental detectors with single-photon resolution are expensive and operate at low temperatures [14].…”