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A quantum gate between a flying optical photon and a single trapped atom


The steady increase in control over individual quantum systems supports the promotion of a quantum technology that could provide functionalities beyond those of any classical device. Two particularly promising applications have been explored during the past decade: photon-based quantum communication, which guarantees unbreakable encryption1 but which still has to be scaled to high rates over large distances, and quantum computation, which will fundamentally enhance computability2 if it can be scaled to a large number of quantum bits (qubits). It was realized early on that a hybrid system of light qubits and matter qubits3 could solve the scalability problem of each field—that of communication by use of quantum repeaters4, and that of computation by use of an optical interconnect between smaller quantum processors5,6. To this end, the development of a robust two-qubit gate that allows the linking of distant computational nodes is “a pressing challenge”6. Here we demonstrate such a quantum gate between the spin state of a single trapped atom and the polarization state of an optical photon contained in a faint laser pulse. The gate mechanism presented7,8 is deterministic and robust, and is expected to be applicable to almost any matter qubit. It is based on reflection of the photonic qubit from a cavity that provides strong light–matter coupling. To demonstrate its versatility, we use the quantum gate to create atom–photon, atom–photon–photon and photon–photon entangled states from separable input states. We expect our experiment to enable various applications, including the generation of atomic9 and photonic10 cluster states and Schrödinger-cat states11, deterministic photonic Bell-state measurements12, scalable quantum computation7 and quantum communication using a redundant quantum parity code13.

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Figure 1: Atom–photon quantum gate.
Figure 2: Entangled atom–photon state generated via the gate operation.
Figure 3: Entangled state between one atom and two photons.
Figure 4: Entangled photon–photon state generated via consecutive interaction with the atom.


  1. Gisin, N., Ribordy, G., Tittel, W. & Zbinden, H. Quantum cryptography. Rev. Mod. Phys. 74, 145–195 (2002)

    ADS  MATH  Google Scholar 

  2. Ladd, T. D. et al. Quantum computers. Nature 464, 45–53 (2010)

    Article  ADS  CAS  Google Scholar 

  3. Duan, L.-M. & Monroe, C. Colloquium: Quantum networks with trapped ions. Rev. Mod. Phys. 82, 1209–1224 (2010)

    Article  ADS  Google Scholar 

  4. Briegel, H.-J., Dür, W., Cirac, J. I. & Zoller, P. Quantum repeaters: the role of imperfect local operations in quantum communication. Phys. Rev. Lett. 81, 5932–5935 (1998)

    Article  ADS  CAS  Google Scholar 

  5. Monroe, C. & Kim, J. Scaling the ion trap quantum processor. Science 339, 1164–1169 (2013)

    Article  ADS  CAS  Google Scholar 

  6. Awschalom, D. D., Bassett, L. C., Dzurak, A. S., Hu, E. L. & Petta, J. R. Quantum spintronics: engineering and manipulating atom-like spins in semiconductors. Science 339, 1174–1179 (2013)

    Article  ADS  CAS  Google Scholar 

  7. Duan, L.-M. & Kimble, H. J. Scalable photonic quantum computation through cavity-assisted interactions. Phys. Rev. Lett. 92, 127902 (2004)

    Article  ADS  Google Scholar 

  8. Reiserer, A., Ritter, S. & Rempe, G. Nondestructive detection of an optical photon. Science 342, 1349–1351 (2013)

    Article  ADS  CAS  Google Scholar 

  9. Cho, J. & Lee, H.-W. Generation of atomic cluster states through the cavity input-output process. Phys. Rev. Lett. 95, 160501 (2005)

    Article  ADS  Google Scholar 

  10. Hu, C. Y., Munro, W. J. & Rarity, J. G. Deterministic photon entangler using a charged quantum dot inside a microcavity. Phys. Rev. B 78, 125318 (2008)

    Article  ADS  Google Scholar 

  11. Wang, B. & Duan, L.-M. Engineering superpositions of coherent states in coherent optical pulses through cavity-assisted interaction. Phys. Rev. A 72, 022320 (2005)

    Article  ADS  Google Scholar 

  12. Bonato, C. et al. CNOT and Bell-state analysis in the weak-coupling cavity QED regime. Phys. Rev. Lett. 104, 160503 (2010)

    Article  ADS  Google Scholar 

  13. Munro, W. J., Stephens, A. M., Devitt, S. J., Harrison, K. A. & Nemoto, K. Quantum communication without the necessity of quantum memories. Nature Photon. 6, 777–781 (2012)

    Article  ADS  CAS  Google Scholar 

  14. Turchette, Q. A., Hood, C. J., Lange, W., Mabuchi, H. & Kimble, H. J. Measurement of conditional phase shifts for quantum logic. Phys. Rev. Lett. 75, 4710–4713 (1995)

    Article  ADS  MathSciNet  CAS  Google Scholar 

  15. Fushman, I. et al. Controlled phase shifts with a single quantum dot. Science 320, 769–772 (2008)

    Article  ADS  CAS  Google Scholar 

  16. Reiserer, A., Nölleke, C., Ritter, S. & Rempe, G. Ground-state cooling of a single atom at the center of an optical cavity. Phys. Rev. Lett. 110, 223003 (2013)

    Article  ADS  Google Scholar 

  17. Paris, M. & Řeháček, J. Quantum State Estimation (Springer, 2004)

    Book  Google Scholar 

  18. Duan, L.-M. & Raussendorf, R. Efficient quantum computation with probabilistic quantum gates. Phys. Rev. Lett. 95, 080503 (2005)

    Article  ADS  MathSciNet  Google Scholar 

  19. van Enk, S. J., Cirac, J. I. & Zoller, P. Photonic channels for quantum communication. Science 279, 205–208 (1998)

    Article  ADS  CAS  Google Scholar 

  20. Dayan, B. et al. A photon turnstile dynamically regulated by one atom. Science 319, 1062–1065 (2008)

    Article  ADS  CAS  Google Scholar 

  21. Volz, J., Gehr, R., Dubois, G., Estéve, J. & Reichel, J. Measurement of the internal state of a single atom without energy exchange. Nature 475, 210–213 (2011)

    Article  CAS  Google Scholar 

  22. Thompson, J. D. et al. Coupling a single trapped atom to a nanoscale optical cavity. Science 340, 1202–1205 (2013)

    Article  ADS  CAS  Google Scholar 

  23. O'Shea, D., Junge, C., Volz, J. & Rauschenbeutel, A. Fiber-optical switch controlled by a single atom. Phys. Rev. Lett. 111, 193601 (2013)

    Article  ADS  Google Scholar 

  24. Rauschenbeutel, A. et al. Step-by-step engineered multiparticle entanglement. Science 288, 2024–2028 (2000)

    Article  ADS  CAS  Google Scholar 

  25. Xiao, Y.-F. et al. Realizing quantum controlled phase flip through cavity QED. Phys. Rev. A 70, 042314 (2004)

    Article  ADS  Google Scholar 

  26. Duan, L.-M., Wang, B. & Kimble, H. J. Robust quantum gates on neutral atoms with cavity-assisted photon scattering. Phys. Rev. A 72, 032333 (2005)

    Article  ADS  Google Scholar 

  27. Xue, P. & Xiao, Y.-F. Universal quantum computation in decoherence-free subspace with neutral atoms. Phys. Rev. Lett. 97, 140501 (2006)

    Article  ADS  Google Scholar 

  28. Olmschenk, S. et al. Quantum teleportation between distant matter qubits. Science 323, 486–489 (2009)

    Article  ADS  CAS  Google Scholar 

  29. Nölleke, C. et al. Efficient teleportation between remote single-atom quantum memories. Phys. Rev. Lett. 110, 140403 (2013)

    Article  ADS  Google Scholar 

  30. Ritter, S. et al. An elementary quantum network of single atoms in optical cavities. Nature 484, 195–200 (2012)

    Article  ADS  CAS  Google Scholar 

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This work was supported by the European Union (Collaborative Project SIQS) and by the Bundesministerium für Bildung und Forschung via IKT 2020 (QK_QuOReP).

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All authors contributed to the experiment, the analysis of the results and the writing of the manuscript.

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Correspondence to Gerhard Rempe.

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The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Detection of the atomic state.

The atom is prepared either in the resonant |2, 2〉 state (blue) or in the detuned F = 1 state (red) and a resonant laser is applied for 3 µs from the side of the cavity. The number of photons detected in the cavity output allows us to distinguish the two cases with a fidelity of 99.65%.

Extended Data Figure 2 Ramsey spectroscopy.

The atom is prepared in the state |2, 2〉 and two π/2 Raman pulses are applied with a temporal separation of 7.5 µs. As the Raman laser detuning is scanned, a sinusoidal oscillation is observed. The error bars denote the s.e.m. When the second pulse is applied with a phase shift of π/2 (red), the curve is shifted by a quarter of a period with respect to the case without phase shift (black). From the amplitude of the sinusoidal fit curves, we deduce that the atomic state preparation, rotation and readout works as intended in 95(1)% of the experiments.

Extended Data Table 1 Numerical values of the truth table and density matrices

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Reiserer, A., Kalb, N., Rempe, G. et al. A quantum gate between a flying optical photon and a single trapped atom. Nature 508, 237–240 (2014).

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