Deterministic quantum teleportation of photonic quantum bits by a hybrid technique

Journal name:
Nature
Volume:
500,
Pages:
315–318
Date published:
DOI:
doi:10.1038/nature12366
Received
Accepted
Published online

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.

At a glance

Figures

  1. Experimental set-up.
    Figure 1: Experimental set-up.

    A time-bin qubit is heralded by detecting one half of an entangled photon pair produced by an optical parametric oscillator (OPO). The continuous-variable teleporter (g, feedforward gain) always transfers this qubit, albeit with non-unit fidelity. The teleported qubit is finally characterized by single or dual homodyne measurement to verify the success of teleportation. See Methods Summary for details. APD, avalanche photodiode; EOM, electro-optic modulator; HD, homodyne detector; LO-x and LO-p, local oscillators to measure x and p quadratures, respectively.

  2. Experimental density matrices.
    Figure 2: Experimental density matrices.

    By means of homodyne tomography, two-mode density matrices are reconstructed both for the input and the output states in photon-number bases24: . The bars show the real or imaginary parts of each matrix element ρklmn. Blue, red and green bars correspond to the vacuum, qubit and multiphoton components, respectively. a, Input state, |ψ1right fence. bd, Output states for different values of r and g.

  3. Experimental results of teleportation including gain tuning.
    Figure 3: Experimental results of teleportation including gain tuning.

    The horizontal axis, showing g, uses a logarithmic scale. Orange and green bars respectively represent qubit and multiphoton components of the teleported states (the left-hand vertical axis). Red diamonds and blue circles with error bars (1s.d.) correspond to Fqubit and Fstate, respectively (the right-hand vertical axis). Theoretical fidelity curves (Supplementary Information) are also plotted, in the same colours. All observed Fqubit values significantly exceed the classical limit of 2/3. For g = 0.79, Fstate>1η/3 and, thus, unconditional teleportation is demonstrated.

References

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Affiliations

  1. Department of Applied Physics, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

    • Shuntaro Takeda,
    • Takahiro Mizuta,
    • Maria Fuwa &
    • Akira Furusawa
  2. Institute of Physics, Johannes-Gutenberg Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany

    • Peter van Loock

Contributions

A.F. planned and supervised the project. P.v.L. and S.T. theoretically defined the scientific goals. S.T. and T.M. designed and performed the experiment, and acquired the data. S.T. and M.F. developed the electronic devices. S.T., T.M. and M.F. analysed the data. S.T. and P.v.L. wrote the manuscript with assistance from all other co-authors.

Competing financial interests

The authors declare no competing financial interests.

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Supplementary information

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  1. Supplementary Information (1.9 MB)

    This file contains a Supplementary Discussion, Supplementary Data, Supplementary References, Supplementary Figures 1-2 and Supplementary Tables 1-2.

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