## Two-photon quantum interference in the 1.5 *μ*m telecommunication band

Optics Express, Vol. 15, Issue 12, pp. 7591-7595 (2007)

http://dx.doi.org/10.1364/OE.15.007591

Acrobat PDF (151 KB)

### Abstract

We report on two-photon quantum interference experiments in the standard telecommunication band. Two identical photons in the 1.5 *μ*m wavelength band were generated in spatially separated modes by a type-I spontaneous parametric down-conversion process, and injected into a fiber-optic Hong-Ou-Mandel interferometer. Two-photon interference patterns of dip and spatial beating in the coincidence counting rate were observed by varying the difference in optical path lengths. The visibilities obtained in the net coincidences were close to the theoretical value of 100%. The raw visibilities were also well above the classical limit.

© 2007 Optical Society of America

## 1. Introduction

2. L. Mandel, “Quantum effects in one-photon and two-photon interference,” Rev. Mod. Phys. **71**, S274–S282 (1999). [CrossRef]

3. A. Zeilinger, “Experiment and the foundations of quantum physics,” Rev. Mod. Phys. **71**, S288–S297 (1999). [CrossRef]

4. C. K. Hong, Z. Y. Ou, and L. Mandel, “Measurement of subpicosecond time intervals between two photons by interference,” Phys. Rev. Lett. **59**, 2044–2046 (1987). [CrossRef] [PubMed]

6. N. Gisin, G. Ribordy, W. Tittel, and H. Zbinden, “Quantum cryptography,” Rev. Mod. Phys. **74**, 145–195 (2002). [CrossRef]

7. E. Knill, R. Laflamme, and G. J. Milburn, “A scheme for efficient quantum computation with linear optics,” Nature **409**, 46–52 (2001). [CrossRef] [PubMed]

8. P. Kok, W. J. Munro, K. Nemoto, T. C. Ralph, J. P. Dowling, and G. J. Milburn, “Linear optical quantum computing with photonic qubits,” Rev. Mod. Phys. **79**, 135–174 (2007). [CrossRef]

9. O. Landry, J. A. W. van Houwelingen, A. Beveratos, H. Zbinden, and N. Gisin, “Quantum teleportation over the Swisscom telecommunication network,” J. Opt. Soc. Am. B , **24**, 398–403 (2007). [CrossRef]

10. H. de Riedmatten, I. Marcikic, J. A. W. van Houwelingen, W. Tittel, H. Zbinden, and N. Gisin, “Long-distance entanglement swapping with photons from separated sources,” Phys. Rev. A , **71**, 050302(R) (2005). [CrossRef]

11. M. Halder, S. Tanzilli, H. de Riedmatten, A. Beveratos, H. Zbinden, and N. Gisin, “Photon-bunching measurement after two 25-km-long optical fibers,” Phys. Rev. A **71**, 042335 (2005). [CrossRef]

12. H. de Riedmatten, I. Marcikic, W. Tittel, H. Zbinden, D. Collins, and N. Gisin, “Long distance quantum teleportation in a quantum relay configuration,” Phys. Rev. Lett. , **92**, 047904 (2004). [CrossRef] [PubMed]

13. I. Marcikic, H. de Riedmatten, W. Tittel, H. Zbinden, and N. Gisin, “Long-distance teleportation of qubits at telecommunication wavelengths,” Nature **421**, 509–513 (2003). [CrossRef] [PubMed]

14. Z. Y. Ou and L. Mandel, “Observation of spatial quantum beating with separated photodetectors,” Phys. Rev. Lett. **61**, 54–57 (1988). [CrossRef] [PubMed]

*μ*m telecom band using a noncollinear spontaneous parametric down-conversion process [15

15. T.-G. Noh, H. Kim, C. J. Youn, S.-B. Cho, J. Hong, T. Zyung, and J. Kim, “Noncollinear correlated photon pair source in the 1550 nm telecommunication band,” Opt. Express **14**, 2805–2810 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-7-2805. [CrossRef] [PubMed]

## 2. Experimental setup

*μ*m wavelength band. The range of the collected bandwidth was estimated to be several hundred nanometers in this configuration. Details of the two-photon creation and collection procedure are similar to those of Ref. [15

15. T.-G. Noh, H. Kim, C. J. Youn, S.-B. Cho, J. Hong, T. Zyung, and J. Kim, “Noncollinear correlated photon pair source in the 1550 nm telecommunication band,” Opt. Express **14**, 2805–2810 (2006), http://www.opticsinfobase.org/abstract.cfm?URI=oe-14-7-2805. [CrossRef] [PubMed]

*μ*m band. The cascaded CWDM filter divides the signal into four channels centered at 1510, 1530, 1550, and 1570 nm, with 18 nm passband width at 3 dB. Thus, the filter sets allow easy choice of the operating frequencies without affecting the remaining parts of the setup. After passing through the WDM filter set, each signal or idler photon was detected by the InGaAs/InP avalanche photodiode (APD) module. The APD modules operated in a gated Geiger mode with the trigger signals derived from the pump laser after lowering the signal rate from 75 MHz to 3.95 MHz. The output signals from the two APD modules and their coincidences within a 5 ns timing window were counted simultaneously.

## 3. Experimental results and analysis

14. Z. Y. Ou and L. Mandel, “Observation of spatial quantum beating with separated photodetectors,” Phys. Rev. Lett. **61**, 54–57 (1988). [CrossRef] [PubMed]

*A*is a constant,

*V*is the visibility, and

*δτ*is the optical time delay between the two paths from the crystal to the beam splitter.

*ω*

_{1}and

*ω*

_{2}are the center frequencies of the passbands of the two CWDM filters. They should be conjugates satisfying the phase matching condition

*ω*

_{1}+

*ω*

_{2}=

*ω*, where

_{p}*ω*is the pump laser frequency. The passband frequency responses of the CWDM filters are assumed to be Gaussian with rms widths

_{p}*σ*.

*μ*m. The theoretical value estimated from the 18 nm passband of the CWDM filters is 118

*μ*m. The observed dip showed a slight deviation from the usual Gaussian shape. This is because the spectral shapes of the CWDM filters are not well approximated by Gaussian functions. Note that if the CWDM filters had rectangular frequency responses, the dip shape would be a sinc function. In our experiment, however, the spectral shapes were very complex and not well approximated by either of these simple functions.

*μ*m, which is in agreement with the theoretically estimated value of 60

*μ*m considering the wavelength difference of 40 nm. The FWHM of the Gaussian envelope was 102.6±2.1

*μ*m. This can be compared with the dip width 104.5 nm in Fig. 2(a).

## 4. Conclusion

*μ*m band were prepared with spatially separated modes using a type-I spontaneous parametric down-conversion process, and then injected into the two input ports of a fiber-optic beam splitter. The mode-matching difficulties in the beam splitter, which are usually encountered in free-space HOM experiments, could be easily overcome by using fiber-optic techniques. Hence, we could obtain almost perfect non-classical two-photon interference patterns of dip and spatial beating in the coincidence counting rate. The visibilities obtained were near the theoretical value of 100%. It is worth noting that the raw visibilities can also be further improved by decreasing the pump power [16].

## Acknowledgments

## References and links

1. | L. Mandel and E. Wolf, |

2. | L. Mandel, “Quantum effects in one-photon and two-photon interference,” Rev. Mod. Phys. |

3. | A. Zeilinger, “Experiment and the foundations of quantum physics,” Rev. Mod. Phys. |

4. | C. K. Hong, Z. Y. Ou, and L. Mandel, “Measurement of subpicosecond time intervals between two photons by interference,” Phys. Rev. Lett. |

5. | D. Bouwmeester, A. Ekert, and A. Zeilinger, eds., |

6. | N. Gisin, G. Ribordy, W. Tittel, and H. Zbinden, “Quantum cryptography,” Rev. Mod. Phys. |

7. | E. Knill, R. Laflamme, and G. J. Milburn, “A scheme for efficient quantum computation with linear optics,” Nature |

8. | P. Kok, W. J. Munro, K. Nemoto, T. C. Ralph, J. P. Dowling, and G. J. Milburn, “Linear optical quantum computing with photonic qubits,” Rev. Mod. Phys. |

9. | O. Landry, J. A. W. van Houwelingen, A. Beveratos, H. Zbinden, and N. Gisin, “Quantum teleportation over the Swisscom telecommunication network,” J. Opt. Soc. Am. B , |

10. | H. de Riedmatten, I. Marcikic, J. A. W. van Houwelingen, W. Tittel, H. Zbinden, and N. Gisin, “Long-distance entanglement swapping with photons from separated sources,” Phys. Rev. A , |

11. | M. Halder, S. Tanzilli, H. de Riedmatten, A. Beveratos, H. Zbinden, and N. Gisin, “Photon-bunching measurement after two 25-km-long optical fibers,” Phys. Rev. A |

12. | H. de Riedmatten, I. Marcikic, W. Tittel, H. Zbinden, D. Collins, and N. Gisin, “Long distance quantum teleportation in a quantum relay configuration,” Phys. Rev. Lett. , |

13. | I. Marcikic, H. de Riedmatten, W. Tittel, H. Zbinden, and N. Gisin, “Long-distance teleportation of qubits at telecommunication wavelengths,” Nature |

14. | Z. Y. Ou and L. Mandel, “Observation of spatial quantum beating with separated photodetectors,” Phys. Rev. Lett. |

15. | T.-G. Noh, H. Kim, C. J. Youn, S.-B. Cho, J. Hong, T. Zyung, and J. Kim, “Noncollinear correlated photon pair source in the 1550 nm telecommunication band,” Opt. Express |

16. | Note that the effects of accidental coincidences can be reduced by decreasing the pump power (Ref. [15]). |

17. | J. Chen, K. F. Lee, and P. Kumar, “Generation of telecom-band indistinguishable photon pairs in dispersion-shifted fiber,” in |

**OCIS Codes**

(190.4410) Nonlinear optics : Nonlinear optics, parametric processes

(270.0270) Quantum optics : Quantum optics

(270.5290) Quantum optics : Photon statistics

**ToC Category:**

Quantum Optics

**History**

Original Manuscript: April 30, 2007

Revised Manuscript: May 28, 2007

Manuscript Accepted: June 2, 2007

Published: June 5, 2007

**Citation**

Seok-Beom Cho and Tae-Gon Noh, "Two-photon quantum interference in the 1.5 μm telecommunication band," Opt. Express **15**, 7591-7595 (2007)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-12-7591

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### References

- L. Mandel and E. Wolf, Optical Coherence and Quantum Optics (Cambridge University Press, Cambridge, UK, 1995).
- L. Mandel, "Quantum effects in one-photon and two-photon interference," Rev. Mod. Phys. 71, S274-S282 (1999). [CrossRef]
- A. Zeilinger, "Experiment and the foundations of quantum physics," Rev. Mod. Phys. 71, S288-S297 (1999). [CrossRef]
- C. K. Hong, Z. Y. Ou, and L. Mandel, "Measurement of subpicosecond time intervals between two photons by interference," Phys. Rev. Lett. 59, 2044-2046 (1987). [CrossRef] [PubMed]
- D. Bouwmeester, A. Ekert, and A. Zeilinger, eds., The Physics of Quantum Information (Springer-Verlag, Berlin, 2000).
- N. Gisin, G. Ribordy,W. Tittel, and H. Zbinden, "Quantum cryptography," Rev. Mod. Phys. 74, 145-195 (2002). [CrossRef]
- E. Knill, R. Laflamme, and G. J. Milburn, "A scheme for efficient quantum computation with linear optics," Nature 409, 46-52 (2001). [CrossRef] [PubMed]
- P. Kok, W. J. Munro, K. Nemoto, T. C. Ralph, J. P. Dowling, and G. J. Milburn, "Linear optical quantum computing with photonic qubits," Rev. Mod. Phys. 79, 135-174 (2007). [CrossRef]
- O. Landry, J. A. W. van Houwelingen, A. Beveratos, H. Zbinden, and N. Gisin, "Quantum teleportation over the Swisscom telecommunication network," J. Opt. Soc. Am. B 24, 398-403 (2007). [CrossRef]
- H. de Riedmatten, I. Marcikic, J. A. W. van Houwelingen, W. Tittel, H. Zbinden, and N. Gisin, "Long-distance entanglement swapping with photons from separated sources," Phys. Rev. A 71, 050302(R) (2005). [CrossRef]
- M. Halder, S. Tanzilli, H. de Riedmatten, A. Beveratos, H. Zbinden, and N. Gisin, "Photon-bunching measurement after two 25-km-long optical fibers," Phys. Rev. A 71, 042335 (2005). [CrossRef]
- H. de Riedmatten, I. Marcikic, W. Tittel, H. Zbinden, D. Collins, and N. Gisin, "Long distance quantum teleportation in a quantum relay configuration," Phys. Rev. Lett. 92, 047904 (2004). [CrossRef] [PubMed]
- I. Marcikic, H. de Riedmatten, W. Tittel, H. Zbinden, and N. Gisin, "Long-distance teleportation of qubits at telecommunication wavelengths," Nature 421, 509-513 (2003). [CrossRef] [PubMed]
- Z. Y. Ou and L. Mandel, "Observation of spatial quantum beating with separated photodetectors," Phys. Rev. Lett. 61, 54-57 (1988). [CrossRef] [PubMed]
- T.-G. Noh, H. Kim, C. J. Youn, S.-B. Cho, J. Hong, T. Zyung, and J. Kim, "Noncollinear correlated photon pair source in the 1550 nm telecommunication band," Opt. Express 14, 2805-2810 (2006). [CrossRef] [PubMed]
- Note that the effects of accidental coincidences can be reduced by decreasing the pump power (Ref. [15]).
- J. Chen, K. F. Lee, and P. Kumar, "Generation of telecom-band indistinguishable photon pairs in dispersionshifted fiber," in Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference and Photonic Applications Systems Technologies 2007 Technical Digest (Optical Society of America, Washington, DC, 2007), paper QTul4; H. Takesue, "1.5-μm band Hong-Ou-Mandel experiment using photon pairs generated in two independent optical fibers," ibid., paper JTuA5.

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