Quantum Inf Process (2014) 13:2171–2193
Secure communication via quantum illumination
Jeffrey H. Shapiro · Zheshen Zhang ·
Franco N. C. Wong
Received: 30 July 2013 / Accepted: 17 October 2013 / Published online: 8 November 2013
© Springer Science+Business Media New York 2013
Abstract In the quantum illumination protocol for secure communication, Alice pre-
pares entangled signal and idler beams via spontaneous parametric downconversion.
She sends the signal beam to Bob, while retaining the idler. Bob imposes message
modulation on the beam he receives from Alice, ampliﬁes it, and sends it back to her.
Alice then decodes Bob’s information by making a joint quantum measurement on the
light she has retained and the light she has received from him. The basic performance
analysis for this protocol—which demonstrates its immunity to passive eavesdrop-
ping, in which Eve can only listen to Alice and Bob’s transmissions—is reviewed,
along with the results of its ﬁrst proof-of-principle experiment. Further analysis is
then presented, showing that secure data rates in excess of 1 Gbps may be possible
over 20-km-long ﬁber links with technology that is available or under development.
Finally, an initial scheme for thwarting active eavesdropping, in which Eve injects her
own light into Bob’s terminal, is proposed and analyzed.
Keywords Secure communication · Entanglement · Spontaneous parametric
downconversion · Optical parametric ampliﬁcation
Governments, businesses, and the general populace are increasingly dependent on
the Internet, and many of their communications thereon need to be protected from
This research was supported by an ONR Basic Research Challenge grant and the DARPA Quiness
J. H. Shapiro (
) · Z. Zhang · F. N. C. Wong
Research Laboratory of Electronics, Massachusetts Institute of Technology,
Cambridge, MA 02139, USA