Data from: Hacking the Bell test using classical light in energy-time entanglement–based quantum key distribution

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.