Quantum key distribution without detector vulnerabilities

Security in quantum cryptography is continuously challenged by inventive attacks targeting the real components of the cryptographic setup. Due to their high sensitivity and complex design, detectors are the most frequently attacked components. It was recently shown [1, 2] that teleportation and two-photon interference can be used to remove any vulnerability from detectors, by essentially transforming a quantum receiver into a quantum transmitter.
This new form of detection-safe quantum key distribution (QKD), termed “measurement-device-independent” (MDI) [2], entails other advantages, e.g., it allows to nearly double the working distance of QKD and to relay two distant users with an untrusted node. The price to pay is often a modest key rate, orders of magnitude smaller than in standard (non-detection-safe) QKD [3-6].
In this colloquium, I will present the rationale behind MDI-QKD, resorting to specific examples from quantum information theory to explain its remarkable features. Afterwards, I will discuss the challenges to be faced to increase the MDI-QKD key rate [7], as well as the technological advances recently introduced to bring it up to the Mb/s range [8].
[1] S. L. Braunstein and S. Pirandola, Phys. Rev. Lett. 108, 130502 (2012).
[2] H.-K. Lo et al., Phys. Rev. Lett. 108, 130503 (2012).
[3] A. Rubenok et al., Phys. Rev. Lett. 111, 130501 (2013).
[4] Y.-L. Tang et al., Phys. Rev. Lett. 113, 190501 (2014).
[5] T. Ferreira da Silva et al., Phys. Rev. A 88, 052303 (2013).
[6] R. Valivarthi et al., J. Mod. Optic. 62, 1141 (2015).
[7] Z. L. Yuan et al., Phys. Rev. Applied 2, 064006 (2014).
[8] L.C. Comandar et al., 10.1038/nphoton.2016.50.