6533b7d6fe1ef96bd126706b

RESEARCH PRODUCT

Deterministic quantum teleportation of photonic quantum bits by a hybrid technique.

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The continuous-variable teleportation of a discrete-variable, photonic qubit is deterministic and allows for faithful qubit transfer even with imperfect continuous-variable entangled states: for four qubits, the overall transfer fidelities all exceed the classical limit of teleportation. Quantum teleportation is one of the most important elementary protocols in quantum information processing. Previous studies have achieved quantum teleportation, but usually randomly and at low rates. Two groups reporting in this issue of Nature have used contrasting methods to achieve the same aim —more efficient quantum teleportation. Takeda et al. describe the experimental realization of fully deterministic, unconditional quantum teleportation of photonic qubits — an optimum choice for information carrying — with overall transfer fidelities exceeding the classical limit of teleportation. The technique may facilitate the development of large-scale optical quantum networks. Steffen et al. report quantum teleportation in a solid-state system, achieving deterministic quantum teleportation in a chip-based superconducting circuit architecture. They teleport quantum states between two macroscopic systems separated by 6 mm at a rate of 10,000 per second, exceeding other reported implementations. Transmission loss in superconducting waveguides is low, so this system should be scalable to significantly larger distances, a step towards quantum communication at microwave frequencies. Quantum teleportation1 allows for the transfer of arbitrary unknown quantum states from a sender to a spatially distant receiver, provided that the two parties share an entangled state and can communicate classically. It is the essence of many sophisticated protocols for quantum communication and computation2,3,4,5. Photons are an optimal choice for carrying information in the form of ‘flying qubits’, but the teleportation of photonic quantum bits6,7,8,9,10,11 (qubits) has been limited by experimental inefficiencies and restrictions. Main disadvantages include the fundamentally probabilistic nature of linear-optics Bell measurements12, as well as the need either to destroy the teleported qubit or attenuate the input qubit when the detectors do not resolve photon numbers13. Here we experimentally realize fully deterministic quantum teleportation of photonic qubits without post-selection. The key step is to make use of a hybrid technique involving continuous-variable teleportation14,15,16 of a discrete-variable, photonic qubit. When the receiver’s feedforward gain is optimally tuned, the continuous-variable teleporter acts as a pure loss channel17,18, and the input dual-rail-encoded qubit, based on a single photon, represents a quantum error detection code against photon loss19 and hence remains completely intact for most teleportation events. This allows for a faithful qubit transfer even with imperfect continuous-variable entangled states: for four qubits the overall transfer fidelities range from 0.79 to 0.82 and all of them exceed the classical limit of teleportation. Furthermore, even for a relatively low level of the entanglement, qubits are teleported much more efficiently than in previous experiments, albeit post-selectively (taking into account only the qubit subspaces), and with a fidelity comparable to the previously reported values.