Sensing intruders using entanglement: a photonic quantum fence

Security against jamming and noise exclusion in imaging

“…The measured and expected visibilities provide data for hypotheses testing based on the likelihood ratio test [20,13]. Our null hypothesis H 0 assumes no intruder while the alternative hypothesis H 1 assumes the presence of interceptresend jamming.…”

“…The noise variance is σ = 0.1. The thin black, red dashed and thick blue lines correspond to the legitimate imagers using two classical states (15) and (16), one entangled and one classical (13) and (15) and two entangled states 13) and (14) respectively. For V L > 0.5 there is no significant difference between imaging with classical and quantum states.…”

“…The states (13) and (14) are entangled while the states (15) and (16) are classically correlated. The coincidence detection probability for (12) is given by…”

“…It may, however, be difficult for the intruder to perform such jamming both efficiently and undetectably. Thus we investigate a weaker jamming procedure in which some of the light from a trusted source of illumination is intercepted by the intruder and replaced by light from their independent source [13,14,15]. As the party who prepares states of light has naturally more information about the states than it is possible to extract from a measurement, the legitimate imager has an informational advantage over the intruder.…”

“…Among them are detection of imaging jamming and appropriate protection [7,8]. In communication situations we can use encryption to safeguard information in transit.…”