## Optimised quantum hacking of superconducting nanowire single-photon detectors |

Optics Express, Vol. 22, Issue 6, pp. 6734-6748 (2014)

http://dx.doi.org/10.1364/OE.22.006734

Acrobat PDF (1567 KB)

### Abstract

We explore bright-light control of superconducting nanowire single-photon detectors (SNSPDs) in the shunted configuration (a practical measure to avoid latching). In an experiment, we simulate an illumination pattern the SNSPD would receive in a typical quantum key distribution system under hacking attack. We show that it effectively blinds and controls the SNSPD. The transient blinding illumination lasts for a fraction of a microsecond and produces several deterministic fake clicks during this time. This attack does not lead to elevated timing jitter in the spoofed output pulse, and hence does not introduce significant errors. Five different SNSPD chip designs were tested. We consider possible countermeasures to this attack.

© 2014 Optical Society of America

## 1. Introduction

2. QKD systems are available for purchase from several companies and research entities. Example commercial manufacturers are ID Quantique (Switzerland), http://www.idquantique.com, and SeQureNet (France), http://www.sequrenet.com/.

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*λ*= 850nm) demonstration was then reported based on the Bennett 1992 (B92) protocol with polarization encoding [7

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9. H. Takesue, S. W. Nam, Q. Zhang, R. H. Hadfield, T. Honjo, K. Tamaki, and Y. Yamamoto, “Quantum key distribution over a 40-dB channel loss using superconducting single-photon detectors,” Nat. Photonics **1**, 343–348 (2007). [CrossRef]

25. A. R. Dixon, Z. L. Yuan, J. F. Dynes, A. W. Sharpe, and A. J. Shields, “Continuous operation of high bit rate quantum key distribution,” Appl. Phys. Lett. **96**, 161102 (2010). [CrossRef]

23. F. Marsili, V. B. Verma, J. A. Stern, S. Harrington, A. E. Lita, T. Gerrits, I. Vayshenker, B. Baek, M. D. Shaw, R. P. Mirin, and S. W. Nam, “Detecting single infrared photons with 93% system efficiency,” Nat. Photonics **7**, 210–214 (2013). [CrossRef]

26. W. K. Wootters and W. H. Zurek, “A single quantum cannot be cloned,” Nature **299**, 802–803 (1982). [CrossRef]

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28. Y. Zhao, C.-H. F. Fung, B. Qi, C. Chen, and H.-K. Lo, “Quantum hacking: Experimental demonstration of time-shift attack against practical quantum-key-distribution systems,” Phys. Rev. A **78**, 042333 (2008). [CrossRef]

33. A. N. Bugge, S. Sauge, A. M. M. Ghazali, J. Skaar, L. Lydersen, and V. Makarov, “Laser damage helps the eavesdropper in quantum cryptography,” Phys. Rev. Lett. **112**, 070503 (2014). [CrossRef] [PubMed]

*et al.*[34

34. L. Lydersen, M. K. Akhlaghi, A. H. Majedi, J. Skaar, and V. Makarov, “Controlling a superconducting nanowire single-photon detector using tailored bright illumination,” New J. Phys. **13**, 113042 (2011). [CrossRef]

35. M. Fujiwara, T. Honjo, K. Shimizu, K. Tamaki, and M. Sasaki, “Characteristics of superconducting single photon detector in DPS-QKD system under bright illumination blinding attack,” Opt. Express **21**, 6304–6312 (2013). [CrossRef] [PubMed]

36. T. Honjo, M. Fujiwara, K. Shimizu, K. Tamaki, S. Miki, T. Yamashita, H. Terai, Z. Wang, and M. Sasaki, “Countermeasure against tailored bright illumination attack for DPS-QKD,” Opt. Express **21**, 2667–2673 (2013). [CrossRef] [PubMed]

6. R. H. Hadfield, J. L. Habif, J. Schlafer, R. E. Schwall, and S. W. Nam, “Quantum key distribution at 1550 nm with twin superconducting single-photon detectors,” Appl. Phys. Lett. **89**, 241129 (2006). [CrossRef]

## 2. Experiment

37. M. Ejrnaes, R. Cristiano, O. Quaranta, S. Pagano, A. Gaggero, F. Mattioli, R. Leoni, B. Voronov, and G. Gol’tsman, “A cascade switching superconducting single photon detector,” Appl. Phys. Lett. **91**, 262509 (2007). [CrossRef]

41. M. Ejrnaes, A. Casaburi, R. Cristiano, O. Quaranta, S. Marchetti, N. Martucciello, S. Pagano, A. Gaggero, F. Mattioli, R. Leoni, P. Cavalier, and J.-C. Villégier, “Timing jitter of cascade switch superconducting nanowire single photon detectors,” Appl. Phys. Lett. **95**, 132503 (2009). [CrossRef]

21. M. Sasaki, M. Fujiwara, H. Ishizuka, W. Klaus, K. Wakui, M. Takeoka, S. Miki, T. Yamashita, Z. Wang, A. Tanaka, K. Yoshino, Y. Nambu, S. Takahashi, A. Tajima, A. Tomita, T. Domeki, T. Hasegawa, Y. Sakai, H. Kobayashi, T. Asai, K. Shimizu, T. Tokura, T. Tsurumaru, M. Matsui, T. Honjo, K. Tamaki, H. Takesue, Y. Tokura, J. F. Dynes, A. R. Dixon, A. W. Sharpe, Z. L. Yuan, A. J. Shields, S. Uchikoga, M. Legré, S. Robyr, P. Trinkler, L. Monat, J.-B. Page, G. Ribordy, A. Poppe, A. Allacher, O. Maurhart, T. Länger, M. Peev, and A. Zeilinger, “Field test of quantum key distribution in the Tokyo QKD Network,” Opt. Express **19**, 10387–10409 (2011). [CrossRef] [PubMed]

22. P. J. Clarke, R. J. Collins, P. A. Hiskett, M. J. Garcia-Martinez, N. J. Krichel, A. McCarthy, M. G. Tanner, J. A. O’Connor, C. M. Natarajan, S. Miki, M. Sasaki, Z. Wang, M. Fujiwara, I. Rech, M. Ghioni, A. Gulinatti, R. H. Hadfield, P. D. Townsend, and G. S. Buller, “Analysis of detector performance in a gigahertz clock rate quantum key distribution system,” New J. Phys. **13**, 075008 (2011). [CrossRef]

42. M. G. Tanner, C. M. Natarajan, V. K. Pottapenjara, J. A. O’Connor, R. J. Warburton, R. H. Hadfield, B. Baek, S. Nam, S. N. Dorenbos, E. B. Ureña, T. Zijlstra, T. M. Klapwijk, and V. Zwiller, “Enhanced telecom wavelength single-photon detection with NbTiN superconducting nanowires on oxidized silicon,” Appl. Phys. Lett. **96**, 221109 (2010). [CrossRef]

6. R. H. Hadfield, J. L. Habif, J. Schlafer, R. E. Schwall, and S. W. Nam, “Quantum key distribution at 1550 nm with twin superconducting single-photon detectors,” Appl. Phys. Lett. **89**, 241129 (2006). [CrossRef]

*R*

_{shunt}that prevents latching (typically a 50Ω resistor) [43

43. R. H. Hadfield, A. J. Miller, S. W. Nam, R. L. Kautz, and R. E. Schwall, “Low-frequency phase locking in high-inductance superconducting nanowires,” Appl. Phys. Lett. **87**, 203505 (2005). [CrossRef]

*R*

_{shunt}. The pulse readout circuit consists of AC-coupled amplifiers with combined gain of 56dB and 10–580MHz frequency range. The detector output signal is observed with an electronic counter and an oscilloscope. The SNSPD is illuminated via single-mode fiber connected to the output of a faked-state generator. The faked-state generator allows the formation of arbitrary illumination diagrams with two distinct optical power levels at the SNSPD, in addition to zero power level. This is achieved with a pulse pattern generator powering two 1550nm laser diodes, followed by optical variable attenuators to set the power levels. The output of the faked-state generator simulates illumination diagrams that the SNSPD would receive if it were a part of a QKD system under attack [34

34. L. Lydersen, M. K. Akhlaghi, A. H. Majedi, J. Skaar, and V. Makarov, “Controlling a superconducting nanowire single-photon detector using tailored bright illumination,” New J. Phys. **13**, 113042 (2011). [CrossRef]

44. J. A. O’Connor, M. G. Tanner, C. M. Natarajan, G. S. Buller, R. J. Warburton, S. Miki, Z. Wang, S. W. Nam, and R. H. Hadfield, “Spatial dependence of output pulse delay in a niobium nitride nanowire superconducting single-photon detector,” Appl. Phys. Lett. **98**, 201116 (2011). [CrossRef]

45. J. K. W. Yang, A. J. Kerman, E. A. Dauler, V. Anant, K. M. Rosfjord, and K. K. Berggren, “Modeling the electrical and thermal response of superconducting nanowire single-photon detectors,” IEEE T. Appl. Supercon. **17**, 581–585 (2007). [CrossRef]

46. F. Marsili, F. Najafi, C. Herder, and K. K. Berggren, “Electrothermal simulation of superconducting nanowire avalanche photodetectors,” Appl. Phys. Lett. **98**, 093507 (2011). [CrossRef]

*et al.*considered artificially generating pulses in SNSPDs through two methods [34

34. L. Lydersen, M. K. Akhlaghi, A. H. Majedi, J. Skaar, and V. Makarov, “Controlling a superconducting nanowire single-photon detector using tailored bright illumination,” New J. Phys. **13**, 113042 (2011). [CrossRef]

43. R. H. Hadfield, A. J. Miller, S. W. Nam, R. L. Kautz, and R. E. Schwall, “Low-frequency phase locking in high-inductance superconducting nanowires,” Appl. Phys. Lett. **87**, 203505 (2005). [CrossRef]

**89**, 241129 (2006). [CrossRef]

*et al.*of blinding the detectors to incoming single photons through continuous bright-light illumination (of the order of 1 to 100 μW in this study depending on individual SNSPD characteristics). We find that with careful control it is possible to generate fake detector output signals reliably on-demand with timing properties better than in the single-photon case.

## 3. Detector control

### 3.1. Applicability to different QKD schemes

47. V. Makarov and D. R. Hjelme, “Faked states attack on quantum cryptosystems,” J. Mod. Optic. **52**, 691–705 (2005). [CrossRef]

48. V. Makarov, “Controlling passively quenched single photon detectors by bright light,” New J. Phys. **11**, 065003 (2009). [CrossRef]

48. V. Makarov, “Controlling passively quenched single photon detectors by bright light,” New J. Phys. **11**, 065003 (2009). [CrossRef]

**13**, 113042 (2011). [CrossRef]

48. V. Makarov, “Controlling passively quenched single photon detectors by bright light,” New J. Phys. **11**, 065003 (2009). [CrossRef]

7. R. J. Collins, R. H. Hadfield, V. Fernandez, S. W. Nam, and G. S. Buller, “Low timing jitter detector for gigahertz quantum key distribution,” Electron. Lett. **43**, 180–182 (2007). [CrossRef]

**1**, 343–348 (2007). [CrossRef]

14. S. Wang, W. Chen, J.-F. Guo, Z.-Q. Yin, H.-W. Li, Z. Zhou, G.-C. Guo, and Z.-F. Han, “2 GHz clock quantum key distribution over 260 km of standard telecom fiber,” Opt. Lett. **37**, 1008–1010 (2012). [CrossRef] [PubMed]

17. Y. Liu, T.-Y. Chen, J. Wang, W.-Q. Cai, X. Wan, L.-K. Chen, J.-H. Wang, S.-B. Liu, H. Liang, L. Yang, C.-Z. Peng, K. Chen, Z.-B. Chen, and J.-W. Pan, “Decoy-state quantum key distribution with polarized photons over 200 km,” Opt. Express **18**, 8587–8594 (2010). [CrossRef] [PubMed]

18. T. Honjo, S. W. Nam, H. Takesue, Q. Zhang, H. Kamada, Y. Nishida, O. Tadanaga, M. Asobe, B. Baek, R. Hadfield, S. Miki, M. Fujiwara, M. Sasaki, Z. Wang, K. Inoue, and Y. Yamamoto, “Long-distance entanglement-based quantum key distribution over optical fiber,” Opt. Express **16**, 19118–19126 (2008). [CrossRef]

20. I. Choi, R. J. Young, and P. D. Townsend, “Quantum key distribution on a 10Gb/s WDM-PON,” Opt. Express **18**, 9600–9612 (2010). [CrossRef] [PubMed]

22. P. J. Clarke, R. J. Collins, P. A. Hiskett, M. J. Garcia-Martinez, N. J. Krichel, A. McCarthy, M. G. Tanner, J. A. O’Connor, C. M. Natarajan, S. Miki, M. Sasaki, Z. Wang, M. Fujiwara, I. Rech, M. Ghioni, A. Gulinatti, R. H. Hadfield, P. D. Townsend, and G. S. Buller, “Analysis of detector performance in a gigahertz clock rate quantum key distribution system,” New J. Phys. **13**, 075008 (2011). [CrossRef]

**89**, 241129 (2006). [CrossRef]

16. D. Rosenberg, C. G. Peterson, J. W. Harrington, P. R. Rice, N. Dallmann, K. T. Tyagi, K. P. McCabe, S. Nam, B. Baek, R. H. Hadfield, R. J. Hughes, and J. E. Nordholt, “Practical long-distance quantum key distribution system using decoy levels,” New J. Phys. **11**, 045009 (2009). [CrossRef]

29. L. Lydersen, C. Wiechers, C. Wittmann, D. Elser, J. Skaar, and V. Makarov, “Hacking commercial quantum cryptography systems by tailored bright illumination,” Nat. Photonics **4**, 686–689 (2010). [CrossRef]

**11**, 065003 (2009). [CrossRef]

12. D. Stucki, N. Walenta, F. Vannel, R. T. Thew, N. Gisin, H. Zbinden, S. Gray, C. R. Towery, and S. Ten, “High rate, long-distance quantum key distribution over 250 km of ultra low loss fibres,” New J. Phys. **11**, 075003 (2009). [CrossRef]

19. A. Tanaka, M. Fujiwara, S. W. Nam, Y. Nambu, S. Takahashi, W. Maeda, K. Yoshino, S. Miki, B. Baek, Z. Wang, A. Tajima, M. Sasaki, and A. Tomita, “Ultra fast quantum key distribution over a 97 km installed telecom fiber with wavelength division multiplexing clock synchronization,” Opt. Express **16**, 11354–11360 (2008). [CrossRef] [PubMed]

49. L. Lydersen, J. Skaar, and V. Makarov, “Tailored bright illumination attack on distributed-phase-reference protocols,” J. Mod. Opt. **58**, 680–685 (2011). [CrossRef]

### 3.2. On-demand fake pulse generation

*I*

^{2}

*L*, where

*I*is the bias current and

*L*is the kinetic inductance of the detector. Once the bias current is shunted out from the detector, the hotspot dissipates on a time scale determined by the rethermalisation of the nanowire with the substrate. This mechanism has been modelled in detail by others [45

45. J. K. W. Yang, A. J. Kerman, E. A. Dauler, V. Anant, K. M. Rosfjord, and K. K. Berggren, “Modeling the electrical and thermal response of superconducting nanowire single-photon detectors,” IEEE T. Appl. Supercon. **17**, 581–585 (2007). [CrossRef]

46. F. Marsili, F. Najafi, C. Herder, and K. K. Berggren, “Electrothermal simulation of superconducting nanowire avalanche photodetectors,” Appl. Phys. Lett. **98**, 093507 (2011). [CrossRef]

*t*∼ −200ns in Fig. 3(b) and 3(e)]. If the bright illumination continues, the detector remains in the resistive state and is no longer sensitive to incident photons. However, if the bright illumination is stopped (or its power is decreased sufficiently, 20dB attenuation is shown to be sufficient in Fig. 3) for a short period of time (e.g., < 50ns), the nanowire rethermalises. It then once more becomes superconducting, and the current starts to return to the detector at a rate defined by the superconducting kinetic inductance of the SNSPD

*L*and the circuit resistance. Recovery of the SNSPD after the blinding attack is somewhat different than recovery from single photon detection. Excess laser power has been absorbed into the detector, driving a large area resistive and causing a local rise in temperature. The need to rethermalise in addition to the normal return of current to the SNSPD extends recovery timescales dependent on the excess blinding energy deposited (or timescale of the attack). If enough of the bias current was allowed to return to the detector, it would once more become single-photon sensitive (after time

*τ*

_{recovery}), and would also exhibit dark counts. Note that it does not require the full bias current to have returned to the nanowire before the detector can exhibit a photoresponse or produce dark counts [23

23. F. Marsili, V. B. Verma, J. A. Stern, S. Harrington, A. E. Lita, T. Gerrits, I. Vayshenker, B. Baek, M. D. Shaw, R. P. Mirin, and S. W. Nam, “Detecting single infrared photons with 93% system efficiency,” Nat. Photonics **7**, 210–214 (2013). [CrossRef]

50. V. Burenkov, H. Xu, B. Qi, R. H. Hadfield, and H.-K. Lo, “Investigations of afterpulsing and detection efficiency recovery in superconducting nanowire single-photon detectors,” J. Appl. Phys. **113**, 213102 (2013). [CrossRef]

*τ*

_{OFF}<

*τ*

_{recovery}optimised experimentally in this work, the proportion of the current that had already returned to the detector is again forced out as the nanowire returns to the resistive state. This elicits another controlled fake output pulse from the detector while maintaining the SNSPD in a ‘blinded’ state. An example of this fake pulse is shown in Fig. 2. This is the basis of the detector attack described in this paper.

### 3.3. Pulse and recovery characteristics

*τ*

_{recovery}, there is a finite probability of a count occurring during the recovery from the blinded state, which is undesirable for full detector control. For the fake pulse outputs demonstrated in this paper,

*τ*

_{OFF}was kept sufficiently below

*τ*

_{recovery}(in this case

*τ*

_{OFF}= 20ns). Then counts due to recovery from the blinded state did not occur during the attack, instead the fake pulse was generated returning the detector to the blinded state. This was confirmed in the good jitter characteristics of the fake pulses, discussed in Section 3.4. Fake pulse amplitude can be increased at the cost of a finite probability of a detector pulse occurring before the intended fake pulse.

*t*> 400ns in Fig. 3), occurring with a probability 10–16% when the detector is blinded for 1–10μs, see Fig. 4. The recovery of the detector from the blinded state is different from normal single-photon detection recovery (which can also stimulate afterpulsing [50

50. V. Burenkov, H. Xu, B. Qi, R. H. Hadfield, and H.-K. Lo, “Investigations of afterpulsing and detection efficiency recovery in superconducting nanowire single-photon detectors,” J. Appl. Phys. **113**, 213102 (2013). [CrossRef]

*t*= 350ns.

*t*= 0ns two fake pulses are generated at a repetition period of 30ns. After the first pulse, 10ns of bright light is required to return the detector to the blinded state before a second fake pulse can be generated with

*τ*

_{OFF}= 20ns. In this manner, fake pulses can be generated at a repetition rate of 33MHz. While these parameters vary between detectors (see last row in Table 1), by the very nature of the attack discussed above

*τ*

_{OFF}is kept well below

*τ*

_{recovery}(in this case at 50%). In normal QKD operation, the maximum single-photon detection rate would be 1/

*τ*

_{recovery}

*with a unity efficiency detector.*The hacker can match or better this rate, with significant further gains available when compared to a non-unity efficiency single photon detector in Bob.

### 3.4. Jitter

*τ*

_{recovery}, the jitter achieved is as good or better than for single-photon response, for all detectors tested. While normal SNSPDs suffer from some variation in timing response over the detector area due to varying hotspot resistance of ∼ 1kΩ [44

44. J. A. O’Connor, M. G. Tanner, C. M. Natarajan, G. S. Buller, R. J. Warburton, S. Miki, Z. Wang, S. W. Nam, and R. H. Hadfield, “Spatial dependence of output pulse delay in a niobium nitride nanowire superconducting single-photon detector,” Appl. Phys. Lett. **98**, 201116 (2011). [CrossRef]

37. M. Ejrnaes, R. Cristiano, O. Quaranta, S. Pagano, A. Gaggero, F. Mattioli, R. Leoni, B. Voronov, and G. Gol’tsman, “A cascade switching superconducting single photon detector,” Appl. Phys. Lett. **91**, 262509 (2007). [CrossRef]

41. M. Ejrnaes, A. Casaburi, R. Cristiano, O. Quaranta, S. Marchetti, N. Martucciello, S. Pagano, A. Gaggero, F. Mattioli, R. Leoni, P. Cavalier, and J.-C. Villégier, “Timing jitter of cascade switch superconducting nanowire single photon detectors,” Appl. Phys. Lett. **95**, 132503 (2009). [CrossRef]

### 3.5. Summary

7. R. J. Collins, R. H. Hadfield, V. Fernandez, S. W. Nam, and G. S. Buller, “Low timing jitter detector for gigahertz quantum key distribution,” Electron. Lett. **43**, 180–182 (2007). [CrossRef]

**1**, 343–348 (2007). [CrossRef]

14. S. Wang, W. Chen, J.-F. Guo, Z.-Q. Yin, H.-W. Li, Z. Zhou, G.-C. Guo, and Z.-F. Han, “2 GHz clock quantum key distribution over 260 km of standard telecom fiber,” Opt. Lett. **37**, 1008–1010 (2012). [CrossRef] [PubMed]

17. Y. Liu, T.-Y. Chen, J. Wang, W.-Q. Cai, X. Wan, L.-K. Chen, J.-H. Wang, S.-B. Liu, H. Liang, L. Yang, C.-Z. Peng, K. Chen, Z.-B. Chen, and J.-W. Pan, “Decoy-state quantum key distribution with polarized photons over 200 km,” Opt. Express **18**, 8587–8594 (2010). [CrossRef] [PubMed]

18. T. Honjo, S. W. Nam, H. Takesue, Q. Zhang, H. Kamada, Y. Nishida, O. Tadanaga, M. Asobe, B. Baek, R. Hadfield, S. Miki, M. Fujiwara, M. Sasaki, Z. Wang, K. Inoue, and Y. Yamamoto, “Long-distance entanglement-based quantum key distribution over optical fiber,” Opt. Express **16**, 19118–19126 (2008). [CrossRef]

20. I. Choi, R. J. Young, and P. D. Townsend, “Quantum key distribution on a 10Gb/s WDM-PON,” Opt. Express **18**, 9600–9612 (2010). [CrossRef] [PubMed]

**13**, 075008 (2011). [CrossRef]

*τ*

_{recovery}and minimum blinding power. For the remaining QKD schemes [6

**89**, 241129 (2006). [CrossRef]

12. D. Stucki, N. Walenta, F. Vannel, R. T. Thew, N. Gisin, H. Zbinden, S. Gray, C. R. Towery, and S. Ten, “High rate, long-distance quantum key distribution over 250 km of ultra low loss fibres,” New J. Phys. **11**, 075003 (2009). [CrossRef]

16. D. Rosenberg, C. G. Peterson, J. W. Harrington, P. R. Rice, N. Dallmann, K. T. Tyagi, K. P. McCabe, S. Nam, B. Baek, R. H. Hadfield, R. J. Hughes, and J. E. Nordholt, “Practical long-distance quantum key distribution system using decoy levels,” New J. Phys. **11**, 045009 (2009). [CrossRef]

19. A. Tanaka, M. Fujiwara, S. W. Nam, Y. Nambu, S. Takahashi, W. Maeda, K. Yoshino, S. Miki, B. Baek, Z. Wang, A. Tajima, M. Sasaki, and A. Tomita, “Ultra fast quantum key distribution over a 97 km installed telecom fiber with wavelength division multiplexing clock synchronization,” Opt. Express **16**, 11354–11360 (2008). [CrossRef] [PubMed]

*τ*

_{recovery}, Eve could try to send faked states tailored to certain sequences of bases. We did not investigate these schemes owing to the lack of a stable reference implementation such as a commercial QKD system that uses SNSPDs.

## 4. Countermeasures

53. H.-K. Lo, M. Curty, and B. Qi, “Measurement-device-independent quantum key distribution,” Phys. Rev. Lett. **108**, 130503 (2012). [CrossRef] [PubMed]

56. Z. L. Yuan, J. F. Dynes, and A. J. Shields, “Resilience of gated avalanche photodiodes against bright illumination attacks in quantum cryptography,” Appl. Phys. Lett. **98**, 231104 (2011). [CrossRef]

*R*

_{shunt}. This manifests itself as a measurable average voltage drop across the DC bias port (measured by voltmeter V2 in Fig. 1), dependent on the duty cycle of the blinding attack. The reading on V2 increased linearly from 0.2mV to 0.5mV with blinding duty cycle varying from 0 to 50%. This is at the limit of the resolution of the standard voltmeter used here. The fractional change in measured resistance was slight in this demonstration especially at short blinding pulse duration (or blinding duty cycle). It can be imagined that more sensitive device monitoring of the correct bandwidth may enable easier detection of attacks that put the detector into a resistive state for a greater time than expected in normal operation. However, it should be noted that in high bit rate QKD the detector will be running at close to its maximum count rate. After each count, during detector recovery, a finite resistance would also be measured on V2. The wise hacker injecting high bit rate fake detector pulses will be aware of this and may be able to keep the blinding duty cycle low, keeping variation on V2 comparable to that caused by high bit rate QKD. It can be imagined that attacks may be limited to short periods of detector blinding.

## 5. Conclusion

## Acknowledgments

## References and links

1. | C. H. Bennett and G. Brassard, “Quantum cryptography: Public key distribution and coin tossing,” in “ |

2. | QKD systems are available for purchase from several companies and research entities. Example commercial manufacturers are ID Quantique (Switzerland), http://www.idquantique.com, and SeQureNet (France), http://www.sequrenet.com/. |

3. | D. Bouwmeester, J.-W. Pan, K. Mattle, M. Eibl, H. Weinfurter, and A. Zeilinger, “Experimental quantum teleportation,” Nature |

4. | S. Barz, E. Kashefi, A. Broadbent, J. F. Fitzsimons, A. Zeilinger, and P. Walther, “Demonstration of blind quantum computing,” Science |

5. | C. M. Natarajan, M. G. Tanner, and R. H. Hadfield, “Superconducting nanowire single-photon detectors: physics and applications,” Supercond. Sci. Tech. |

6. | R. H. Hadfield, J. L. Habif, J. Schlafer, R. E. Schwall, and S. W. Nam, “Quantum key distribution at 1550 nm with twin superconducting single-photon detectors,” Appl. Phys. Lett. |

7. | R. J. Collins, R. H. Hadfield, V. Fernandez, S. W. Nam, and G. S. Buller, “Low timing jitter detector for gigahertz quantum key distribution,” Electron. Lett. |

8. | C. H. Bennett, “Quantum cryptography using any two nonorthogonal states,” Phys. Rev. Lett. |

9. | H. Takesue, S. W. Nam, Q. Zhang, R. H. Hadfield, T. Honjo, K. Tamaki, and Y. Yamamoto, “Quantum key distribution over a 40-dB channel loss using superconducting single-photon detectors,” Nat. Photonics |

10. | K. Inoue, E. Waks, and Y. Yamamoto, “Differential phase shift quantum key distribution,” Phys. Rev. Lett. |

11. | C. Gobby, Z. L. Yuan, and A. J. Shields, “Quantum key distribution over 122 km of standard telecom fiber,” Appl. Phys. Lett. |

12. | D. Stucki, N. Walenta, F. Vannel, R. T. Thew, N. Gisin, H. Zbinden, S. Gray, C. R. Towery, and S. Ten, “High rate, long-distance quantum key distribution over 250 km of ultra low loss fibres,” New J. Phys. |

13. | D. Stucki, C. Barreiro, S. Fasel, J.-D. Gautier, O. Gay, N. Gisin, R. Thew, Y. Thoma, P. Trinkler, F. Vannel, and H. Zbinden, “Continuous high speed coherent one-way quantum key distribution,” Opt. Express |

14. | S. Wang, W. Chen, J.-F. Guo, Z.-Q. Yin, H.-W. Li, Z. Zhou, G.-C. Guo, and Z.-F. Han, “2 GHz clock quantum key distribution over 260 km of standard telecom fiber,” Opt. Lett. |

15. | H.-K. Lo, X. Ma, and K. Chen, “Decoy state quantum key distribution,” Phys. Rev. Lett. |

16. | D. Rosenberg, C. G. Peterson, J. W. Harrington, P. R. Rice, N. Dallmann, K. T. Tyagi, K. P. McCabe, S. Nam, B. Baek, R. H. Hadfield, R. J. Hughes, and J. E. Nordholt, “Practical long-distance quantum key distribution system using decoy levels,” New J. Phys. |

17. | Y. Liu, T.-Y. Chen, J. Wang, W.-Q. Cai, X. Wan, L.-K. Chen, J.-H. Wang, S.-B. Liu, H. Liang, L. Yang, C.-Z. Peng, K. Chen, Z.-B. Chen, and J.-W. Pan, “Decoy-state quantum key distribution with polarized photons over 200 km,” Opt. Express |

18. | T. Honjo, S. W. Nam, H. Takesue, Q. Zhang, H. Kamada, Y. Nishida, O. Tadanaga, M. Asobe, B. Baek, R. Hadfield, S. Miki, M. Fujiwara, M. Sasaki, Z. Wang, K. Inoue, and Y. Yamamoto, “Long-distance entanglement-based quantum key distribution over optical fiber,” Opt. Express |

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20. | I. Choi, R. J. Young, and P. D. Townsend, “Quantum key distribution on a 10Gb/s WDM-PON,” Opt. Express |

21. | M. Sasaki, M. Fujiwara, H. Ishizuka, W. Klaus, K. Wakui, M. Takeoka, S. Miki, T. Yamashita, Z. Wang, A. Tanaka, K. Yoshino, Y. Nambu, S. Takahashi, A. Tajima, A. Tomita, T. Domeki, T. Hasegawa, Y. Sakai, H. Kobayashi, T. Asai, K. Shimizu, T. Tokura, T. Tsurumaru, M. Matsui, T. Honjo, K. Tamaki, H. Takesue, Y. Tokura, J. F. Dynes, A. R. Dixon, A. W. Sharpe, Z. L. Yuan, A. J. Shields, S. Uchikoga, M. Legré, S. Robyr, P. Trinkler, L. Monat, J.-B. Page, G. Ribordy, A. Poppe, A. Allacher, O. Maurhart, T. Länger, M. Peev, and A. Zeilinger, “Field test of quantum key distribution in the Tokyo QKD Network,” Opt. Express |

22. | P. J. Clarke, R. J. Collins, P. A. Hiskett, M. J. Garcia-Martinez, N. J. Krichel, A. McCarthy, M. G. Tanner, J. A. O’Connor, C. M. Natarajan, S. Miki, M. Sasaki, Z. Wang, M. Fujiwara, I. Rech, M. Ghioni, A. Gulinatti, R. H. Hadfield, P. D. Townsend, and G. S. Buller, “Analysis of detector performance in a gigahertz clock rate quantum key distribution system,” New J. Phys. |

23. | F. Marsili, V. B. Verma, J. A. Stern, S. Harrington, A. E. Lita, T. Gerrits, I. Vayshenker, B. Baek, M. D. Shaw, R. P. Mirin, and S. W. Nam, “Detecting single infrared photons with 93% system efficiency,” Nat. Photonics |

24. | F. Bussières, C. Clausen, A. Tiranov, B. Korzh, V. B. Verma, S. W. Nam, F. Marsili, A. Ferrier, P. Goldner, H. Herrmann, C. Silberhorn, W. Sohler, M. Afzelius, and N. Gisin, “Quantum teleportation from a telecom-wavelength photon to a solid-state quantum memory,” (2014). arXiv:1401.6958 [quant-ph]. |

25. | A. R. Dixon, Z. L. Yuan, J. F. Dynes, A. W. Sharpe, and A. J. Shields, “Continuous operation of high bit rate quantum key distribution,” Appl. Phys. Lett. |

26. | W. K. Wootters and W. H. Zurek, “A single quantum cannot be cloned,” Nature |

27. | V. Scarani, H. Bechmann-Pasquinucci, N. J. Cerf, M. Dušek, N. Lütkenhaus, and M. Peev, “The security of practical quantum key distribution,” Rev. Mod. Phys. |

28. | Y. Zhao, C.-H. F. Fung, B. Qi, C. Chen, and H.-K. Lo, “Quantum hacking: Experimental demonstration of time-shift attack against practical quantum-key-distribution systems,” Phys. Rev. A |

29. | L. Lydersen, C. Wiechers, C. Wittmann, D. Elser, J. Skaar, and V. Makarov, “Hacking commercial quantum cryptography systems by tailored bright illumination,” Nat. Photonics |

30. | L. Lydersen, C. Wiechers, C. Wittmann, D. Elser, J. Skaar, and V. Makarov, “Thermal blinding of gated detectors in quantum cryptography,” Opt. Express |

31. | H. Weier, H. Krauss, M. Rau, M. Fürst, S. Nauerth, and H. Weinfurter, “Quantum eavesdropping without interception: an attack exploiting the dead time of single-photon detectors,” New J. Phys. |

32. | M.-S. Jiang, S.-H. Sun, G.-Z. Tang, X.-C. Ma, C.-Y. Li, and L.-M. Liang, “Intrinsic imperfection of self-differencing single-photon detectors harms the security of high-speed quantum cryptography systems,” Phys. Rev. A |

33. | A. N. Bugge, S. Sauge, A. M. M. Ghazali, J. Skaar, L. Lydersen, and V. Makarov, “Laser damage helps the eavesdropper in quantum cryptography,” Phys. Rev. Lett. |

34. | L. Lydersen, M. K. Akhlaghi, A. H. Majedi, J. Skaar, and V. Makarov, “Controlling a superconducting nanowire single-photon detector using tailored bright illumination,” New J. Phys. |

35. | M. Fujiwara, T. Honjo, K. Shimizu, K. Tamaki, and M. Sasaki, “Characteristics of superconducting single photon detector in DPS-QKD system under bright illumination blinding attack,” Opt. Express |

36. | T. Honjo, M. Fujiwara, K. Shimizu, K. Tamaki, S. Miki, T. Yamashita, H. Terai, Z. Wang, and M. Sasaki, “Countermeasure against tailored bright illumination attack for DPS-QKD,” Opt. Express |

37. | M. Ejrnaes, R. Cristiano, O. Quaranta, S. Pagano, A. Gaggero, F. Mattioli, R. Leoni, B. Voronov, and G. Gol’tsman, “A cascade switching superconducting single photon detector,” Appl. Phys. Lett. |

38. | F. Marsili, F. Najafi, E. Dauler, F. Bellei, X. L. Hu, M. Csete, R. J. Molnar, and K. K. Berggren, “Single-photon detectors based on ultranarrow superconducting nanowires,” Nano Lett. |

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40. | R. M. Heath, M. G. Tanner, A. Casaburi, M. G. Webster, L. San Emeterio Alvarez, W. Jiang, Z. H. Barber, R. J. Warburton, and R. H. Hadfield, “Nano-optical observation of cascade switching in a parallel superconducting nanowire single photon detector,” Appl. Phys. Lett. |

41. | M. Ejrnaes, A. Casaburi, R. Cristiano, O. Quaranta, S. Marchetti, N. Martucciello, S. Pagano, A. Gaggero, F. Mattioli, R. Leoni, P. Cavalier, and J.-C. Villégier, “Timing jitter of cascade switch superconducting nanowire single photon detectors,” Appl. Phys. Lett. |

42. | M. G. Tanner, C. M. Natarajan, V. K. Pottapenjara, J. A. O’Connor, R. J. Warburton, R. H. Hadfield, B. Baek, S. Nam, S. N. Dorenbos, E. B. Ureña, T. Zijlstra, T. M. Klapwijk, and V. Zwiller, “Enhanced telecom wavelength single-photon detection with NbTiN superconducting nanowires on oxidized silicon,” Appl. Phys. Lett. |

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44. | J. A. O’Connor, M. G. Tanner, C. M. Natarajan, G. S. Buller, R. J. Warburton, S. Miki, Z. Wang, S. W. Nam, and R. H. Hadfield, “Spatial dependence of output pulse delay in a niobium nitride nanowire superconducting single-photon detector,” Appl. Phys. Lett. |

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50. | V. Burenkov, H. Xu, B. Qi, R. H. Hadfield, and H.-K. Lo, “Investigations of afterpulsing and detection efficiency recovery in superconducting nanowire single-photon detectors,” J. Appl. Phys. |

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53. | H.-K. Lo, M. Curty, and B. Qi, “Measurement-device-independent quantum key distribution,” Phys. Rev. Lett. |

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56. | Z. L. Yuan, J. F. Dynes, and A. J. Shields, “Resilience of gated avalanche photodiodes against bright illumination attacks in quantum cryptography,” Appl. Phys. Lett. |

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58. | Z. L. Yuan, J. F. Dynes, and A. J. Shields, “Reply to “Comment on ‘Resilience of gated avalanche photodiodes against bright illumination attacks in quantum cryptography’”,” Appl. Phys. Lett. |

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**OCIS Codes**

(030.5260) Coherence and statistical optics : Photon counting

(270.5570) Quantum optics : Quantum detectors

(270.5568) Quantum optics : Quantum cryptography

**ToC Category:**

Quantum Optics

**History**

Original Manuscript: January 14, 2014

Revised Manuscript: March 5, 2014

Manuscript Accepted: March 5, 2014

Published: March 14, 2014

**Citation**

Michael G. Tanner, Vadim Makarov, and Robert H. Hadfield, "Optimised quantum hacking of superconducting nanowire single-photon detectors," Opt. Express **22**, 6734-6748 (2014)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-6-6734

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### References

- C. H. Bennett, G. Brassard, “Quantum cryptography: Public key distribution and coin tossing,” in “Proceedings of IEEE International Conference on Computers, Systems, and Signal Processing,” (IEEE Press, New York, Bangalore, India, 1984), pp. 175–179.
- QKD systems are available for purchase from several companies and research entities. Example commercial manufacturers are ID Quantique (Switzerland), http://www.idquantique.com , and SeQureNet (France), http://www.sequrenet.com/ .
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- F. Bussières, C. Clausen, A. Tiranov, B. Korzh, V. B. Verma, S. W. Nam, F. Marsili, A. Ferrier, P. Goldner, H. Herrmann, C. Silberhorn, W. Sohler, M. Afzelius, N. Gisin, “Quantum teleportation from a telecom-wavelength photon to a solid-state quantum memory,” (2014). arXiv:1401.6958 [quant-ph].
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