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Photonic quantum state transfer between a cold atomic gas and a crystal


Interfacing fundamentally different quantum systems is key to building future hybrid quantum networks1. Such heterogeneous networks offer capabilities superior to those of their homogeneous counterparts, as they merge the individual advantages of disparate quantum nodes in a single network architecture2. However, few investigations of optical hybrid interconnections have been carried out, owing to fundamental and technological challenges such as wavelength and bandwidth matching of the interfacing photons. Here we report optical quantum interconnection of two disparate matter quantum systems with photon storage capabilities. We show that a quantum state can be transferred faithfully between a cold atomic ensemble3,4 and a rare-earth-doped crystal5,6,7,8 by means of a single photon at 1,552 nanometre telecommunication wavelength, using cascaded quantum frequency conversion. We demonstrate that quantum correlations between a photon and a single collective spin excitation in the cold atomic ensemble can be transferred to the solid-state system. We also show that single-photon time-bin qubits generated in the cold atomic ensemble can be converted, stored and retrieved from the crystal with a conditional qubit fidelity of more than 85 per cent. Our results open up the prospect of optically connecting quantum nodes with different capabilities and represent an important step towards the realization of large-scale hybrid quantum networks.

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Figure 1: Schematic set-up and relevant level schemes.
Figure 2: Photon generation, conversion and storage.
Figure 3: Coherence preservation.
Figure 4: Single-photon qubit transfer.


  1. 1

    Kimble, H. J. The quantum internet. Nature 453, 1023–1030 (2008)

    ADS  CAS  Article  Google Scholar 

  2. 2

    Wallquist, M., Hammerer, K., Rabl, P., Lukin, M. & Zoller, P. Hybrid quantum devices and quantum engineering. Phys. Scr. T137, 014001 (2009)

    ADS  Article  Google Scholar 

  3. 3

    Chou, C. W. et al. Measurement-induced entanglement for excitation stored in remote atomic ensembles. Nature 438, 828–832 (2005)

    ADS  CAS  Article  Google Scholar 

  4. 4

    Chanelière, T. et al. Storage and retrieval of single photons transmitted between remote quantum memories. Nature 438, 833–836 (2005)

    ADS  Article  Google Scholar 

  5. 5

    de Riedmatten, H., Afzelius, M., Staudt, M. U., Simon, C. & Gisin, N. A solid-state light-matter interface at the single-photon level. Nature 456, 773–777 (2008)

    ADS  CAS  Article  Google Scholar 

  6. 6

    Hedges, M. P., Longdell, J. J., Li, Y. & Sellars, M. J. Efficient quantum memory for light. Nature 465, 1052–1056 (2010)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Clausen, C. et al. Quantum storage of photonic entanglement in a crystal. Nature 469, 508–511 (2011)

    ADS  CAS  Article  Google Scholar 

  8. 8

    Saglamyurek, E. et al. Broadband waveguide quantum memory for entangled photons. Nature 469, 512–515 (2011)

    ADS  CAS  Article  Google Scholar 

  9. 9

    Eisaman, M. D. et al. Electromagnetically induced transparency with tunable single-photon pulses. Nature 438, 837–841 (2005)

    ADS  CAS  Article  Google Scholar 

  10. 10

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

    ADS  CAS  Article  Google Scholar 

  11. 11

    Hofmann, J. et al. Heralded entanglement between widely separated atoms. Science 337, 72–75 (2012)

    ADS  CAS  Article  Google Scholar 

  12. 12

    Moehring, D. L. et al. Entanglement of single-atom quantum bits at a distance. Nature 449, 68–71 (2007)

    ADS  CAS  Article  Google Scholar 

  13. 13

    Usmani, I. et al. Heralded quantum entanglement between two crystals. Nat. Photon. 6, 234–237 (2012)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Pfaff, W. et al. Unconditional quantum teleportation between distant solid-state quantum bits. Science 345, 532–535 (2014)

    ADS  MathSciNet  CAS  Article  Google Scholar 

  15. 15

    Delteil, A., Sun, Z., Fält, S. & Imamoğlu, A. Realization of a cascaded quantum system: heralded absorption of a single photon qubit by a single-electron charged quantum dot. Phys. Rev. Lett. 118, 177401 (2017)

    ADS  Article  Google Scholar 

  16. 16

    Xiang, Z.-L., Ashhab, S., You, J. Q. & Nori, F. Hybrid quantum circuits: superconducting circuits interacting with other quantum systems. Rev. Mod. Phys. 85, 623–653 (2013)

    ADS  CAS  Article  Google Scholar 

  17. 17

    Tan, T. R. et al. Multi-element logic gates for trapped-ion qubits. Nature 528, 380–383 (2015)

    ADS  CAS  Article  Google Scholar 

  18. 18

    Ballance, C. J. et al. Hybrid quantum logic and a test of Bell’s inequality using two different atomic isotopes. Nature 528, 384–386 (2015)

    ADS  CAS  Article  Google Scholar 

  19. 19

    Akopian, N., Wang, L., Rastelli, A., Schmidt, O. G. & Zwiller, V. Hybrid semiconductor-atomic interface: slowing down single photons from a quantum dot. Nat. Photon. 5, 230–233 (2011)

    ADS  CAS  Article  Google Scholar 

  20. 20

    Siyushev, P., Stein, G., Wrachtrup, J. & Gerhardt, I. Molecular photons interfaced with alkali atoms. Nature 509, 66–70 (2014)

    ADS  CAS  Article  Google Scholar 

  21. 21

    Meyer, H. M. et al. Direct photonic coupling of a semiconductor quantum dot and a trapped ion. Phys. Rev. Lett. 114, 123001 (2015)

    ADS  CAS  Article  Google Scholar 

  22. 22

    Tang, J.-S. et al. Storage of multiple single-photon pulses emitted from a quantum dot in a solid-state quantum memory. Nat. Commun. 6, 8652 (2015)

    ADS  CAS  Article  Google Scholar 

  23. 23

    Lettner, M. et al. Remote entanglement between a single atom and a Bose–Einstein condensate. Phys. Rev. Lett. 106, 210503 (2011)

    ADS  CAS  Article  Google Scholar 

  24. 24

    Sangouard, N., Simon, C., de Riedmatten, H. & Gisin, N. Quantum repeaters based on atomic ensembles and linear optics. Rev. Mod. Phys. 83, 33–80 (2011)

    ADS  Article  Google Scholar 

  25. 25

    Saffman, M., Walker, T. G. & Mølmer, K. Quantum information with Rydberg atoms. Rev. Mod. Phys. 82, 2313–2363 (2010)

    ADS  CAS  Article  Google Scholar 

  26. 26

    Ferguson, K. R., Beavan, S. E., Longdell, J. J. & Sellars, M. J. Generation of light with multimode time-delayed entanglement using storage in a solid-state spin-wave quantum memory. Phys. Rev. Lett. 117, 020501 (2016)

    ADS  Article  Google Scholar 

  27. 27

    Kutluer, K., Mazzera, M. & de Riedmatten, H. Solid-state source of nonclassical photon pairs with embedded multimode quantum memory. Phys. Rev. Lett. 118, 210502 (2017)

    ADS  Article  Google Scholar 

  28. 28

    Seri, A. et al. Quantum correlations between single telecom photons and a multimode on-demand solid-state quantum memory. Phys. Rev. X 7, 021028 (2017)

    Google Scholar 

  29. 29

    Duan, L. M., Lukin, M. D., Cirac, J. I. & Zoller, P. Long-distance quantum communication with atomic ensembles and linear optics. Nature 414, 413–418 (2001)

    ADS  CAS  Article  Google Scholar 

  30. 30

    Albrecht, B., Farrera, P., Fernandez-Gonzalvo, X., Cristiani, M. & de Riedmatten, H. A waveguide frequency converter connecting rubidium-based quantum memories to the telecom C-band. Nat. Commun. 5, 3376 (2014)

    ADS  Article  Google Scholar 

  31. 31

    Yang, S.-J., Wang, X.-J., Bao, X.-H. & Pan, J.-W. An efficient quantum light–matter interface with sub-second lifetime. Nat. Photon. 10, 381–384 (2016)

    ADS  CAS  Article  Google Scholar 

  32. 32

    Sinclair, N. et al. Proposal and proof-of-principle demonstration of non-destructive detection of photonic qubits using a Tm:LiNbO3 waveguide. Nat. Commun. 7, 13454 (2016)

    ADS  CAS  Article  Google Scholar 

  33. 33

    Farrera, P. et al. Generation of single photons with highly tunable wave shape from a cold atomic ensemble. Nat. Commun. 7, 13556 (2016)

    ADS  CAS  Article  Google Scholar 

  34. 34

    Afzelius, M., Simon, C., de Riedmatten, H. & Gisin, N. Multimode quantum memory based on atomic frequency combs. Phys. Rev. A 79, 052329 (2009)

    ADS  Article  Google Scholar 

  35. 35

    Gündoğan, M., Ledingham, P. M., Kutluer, K., Mazzera, M. & de Riedmatten, H. Solid state spin-wave quantum memory for time-bin qubits. Phys. Rev. Lett. 114, 230501 (2015)

    ADS  Article  Google Scholar 

  36. 36

    James, D. F. V., Kwiat, P. G., Munro, W. J. & White, A. G. Measurement of qubits. Phys. Rev. A 64, 052312 (2001)

    ADS  Article  Google Scholar 

  37. 37

    Massar, S. & Popescu, S. Optimal extraction of information from finite quantum ensembles. Phys. Rev. Lett. 74, 1259–1263 (1995)

    ADS  MathSciNet  CAS  Article  Google Scholar 

  38. 38

    Kumar, P. Quantum frequency conversion. Opt. Lett. 15, 1476 (1990)

    ADS  CAS  Article  Google Scholar 

  39. 39

    Maring, N. et al. Storage of up-converted telecom photons in a doped crystal. New J. Phys. 16, 113021 (2014)

    Article  Google Scholar 

  40. 40

    Minář, J., de Riedmatten, H., Simon, C., Zbinden, H. & Gisin, N. Phase-noise measurements in long-fiber interferometers for quantum-repeater applications. Phys. Rev. A 77, 052325 (2008)

    ADS  Article  Google Scholar 

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This work was supported by the ERC starting grant QuLIMA, by the Spanish Ministry of Economy and Competitiveness (MINECO) and the Fondo Europeo de Desarrollo Regional (FEDER) through grant FIS2015-69535-R, by MINECO Severo Ochoa through grant SEV-2015-0522, by AGAUR via 2014 SGR 1554, by Fundació Privada Cellex and by the CERCA programme of the Generalitat de Catalunya. P.F. acknowledges the International PhD-fellowship program “la Caixa”-Severo Ochoa @ ICFO. G.H. acknowledges support by the ICFOnest international postdoctoral fellowship program.

Author information




N.M. built and operated the QFC set-ups, and P.F. built and operated the atomic quantum memory set-up, both under the supervision of G.H. The solid-state quantum memory set-up was built and operated by K.K. under the supervision of M.M. The experiment was conducted by N.M., P.F., K.K. and G.H., who also jointly analysed the data. G.H., N.M. and H.d.R. wrote the paper, with inputs from all co-authors. H.d.R. conceived the experiment and supervised the project.

Corresponding authors

Correspondence to Georg Heinze or Hugues de Riedmatten.

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The authors declare no competing financial interests.

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Extended data figures and tables

Extended Data Figure 1 Experimental set-up.

On the left, a cold 87Rb quantum memory is operated to generate non-classically correlated photon pairs. In the centre, the single read photons are frequency-converted from 780 nm to 1,550 nm in QFCD1 and afterwards to 606 nm in QFCD2. On the right, the converted read photons are stored and analysed in a crystal before being retrieved and detected. AOM, acousto-optic modulator; BF, bandpass filter; DM, dichroic mirror; Et, etalon; FS, fibre switch; Gr, diffraction grating; λ/2 (λ/4) half (quarter)-wave plate; PBS, polarizing beam splitter; PC, polarization controller; PP, anamorphic prism pair; QM, quantum memory; S, mechanical shutter.

Extended Data Figure 2 Time-bin read photon.

Conditional histogram of a time-bin read photon, taken at pe = 5% after the MOT at site A.

Extended Data Figure 3 AFC storage characterization.

Absorption spectra of AFCs with different periodicities Δ are shown on the left side. Input pulses (200 ns FHWM) derived from the 606 nm preparation laser are sent to the different AFC structures at 0 μs, and their corresponding echoes are shown on the right side. a, . b, . c, Double periodicity with and leading to a double echo at 2 μs and 2.5 μs. OD, optical depth.

Extended Data Figure 4 AFC efficiency and interference versus photon detuning.

Relative storage efficiency of classical light (derived from the 606 nm preparation laser) versus its frequency detuning δ with respect to the centre of the prepared AFC. For the blue dots, the input is a single Gaussian shaped pulse stored in a single AFC. For the green squares, the input is a doubly peaked pulse (mimicking a time-bin input photon) stored on two superimposed AFCs.

Extended Data Figure 5 Experimental time sequence.

First, the AFC in the crystal is prepared (bottom row), before the main experiment involving the cold atomic quantum memory (top row) and the conversion interface (centre row) starts. Eventual detections of write photons at D1 and converted, stored and restored read photons at D2 are indicated by stars.

Extended Data Figure 6 Weak coherent-state measurements.

a, Signal-to-noise ratio of the echo retrieved from the crystal, if a weak coherent state is frequency-converted in the QFCDs and stored in the memory depending on the mean input photon number per pulse before the interface. The green line is a fit with the expected linear behaviour. b, Visibility of interfering weak coherent time-bin pulses depending on their mean input photon number , after the pulses were frequency converted and stored for and in the AFC memory. The green line is the predicted behaviour of the visibility, taking into account the measured signal-to-noise ratio. The inset shows as an example the interference fringe taken at .

Extended Data Figure 7 Interference visibility.

Calculated visibility V0 as a function of the laser linewidth FWHM (2.35σ). The shaded area shows the typical operating range of the experiment.

Extended Data Figure 8 Storage efficiency and cross-correlation versus storage time.

a, Total storage efficiency and b, normalized cross-correlation function of the initial write photon at site A and the converted, stored and retrieved read photon at site B depending on the storage time τB in the crystal, taken at pe ≈ 10%.

Extended Data Table 1 System losses
Extended Data Table 2 Unheralded autocorrelation measurements

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Maring, N., Farrera, P., Kutluer, K. et al. Photonic quantum state transfer between a cold atomic gas and a crystal. Nature 551, 485–488 (2017).

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