Send to

Choose Destination
Sci Adv. 2015 Dec 18;1(11):e1500793. doi: 10.1126/sciadv.1500793. eCollection 2015 Dec.

Hacking the Bell test using classical light in energy-time entanglement-based quantum key distribution.

Author information

Institutionen för Systemteknik, Linköpings Universitet, 581 83 Linköping, Sweden.
Department of Physics, Stockholm University, 106 91 Stockholm, Sweden.


Photonic systems based on energy-time entanglement have been proposed to test local realism using the Bell inequality. A violation of this inequality normally also certifies security of device-independent quantum key distribution (QKD) so that an attacker cannot eavesdrop or control the system. We show how this security test can be circumvented in energy-time entangled systems when using standard avalanche photodetectors, allowing an attacker to compromise the system without leaving a trace. We reach Bell values up to 3.63 at 97.6% faked detector efficiency using tailored pulses of classical light, which exceeds even the quantum prediction. This is the first demonstration of a violation-faking source that gives both tunable violation and high faked detector efficiency. The implications are severe: the standard Clauser-Horne-Shimony-Holt inequality cannot be used to show device-independent security for energy-time entanglement setups based on Franson's configuration. However, device-independent security can be reestablished, and we conclude by listing a number of improved tests and experimental setups that would protect against all current and future attacks of this type.


Bell’s Theorem; Energy-Time Entanglement; Quantum Hacking; Quantum Key Distribution

Supplemental Content

Full text links

Icon for PubMed Central
Loading ...
Support Center