Quantum cryptography for WDM networks: encryption with coherent states and key generation with fiber based entanglement

Eric Corndorf

Paul D. Townsend

Eric Corndorf, Gregory S. Kanter, Chuang Liang +1 more

We demonstrate quantum-noise protected data encryption over a 200km-long inline optically-amplified fiber line at 650Mbps rate using off-the-shelf components. In contrast to our previous implementation, this demonstration uses phase-encoded coherent states, resulting in a polarization independent system that is compatible with the existing WDM infrastructure. Security calculations are presented for individual attacks on both the encrypted data as well as the secret key. This demonstration paves the way for widespread deployment of quantum cryptography in WDM networks.

Paul D. Townsend

Prem Kumar

Keeping in mind the ubiquitous standard optical fiber for long‐distance transmission and the widespread availability of efficient active and passive fiber devices, we have been developing telecom‐band resources for practical quantum communication and cryptography in wave‐division‐multiplexed (WDM) optical networks. In this talk I present our recent results on two fronts: i) telecom‐band in‐fiber entanglement generation, storage, and long‐distance distribution and ii) quantum‐noise protected high‐speed data encryption through an optically‐amplified WDM line. Along the first front, with our in‐fiber entanglement source all four Bell states can be readily produced and we have demonstrated violation of Bell’s inequalities by up to 10 standard deviations of measurement uncertainty. With such a source we have demonstrated storage of entanglement for up to 1/8 of a millisecond. Furthermore, when each photon of the entangled pair is propagated in separate 25km‐long standard fibers, high visibility quantum interference is still observed, demonstrating that this system is capable of long‐distance (> 50 km) entanglement distribution. Along the second front, we have implemented a new quantum cryptographic scheme, based on Yuen’s KCQ protocol, in which the inherent quantum noise of coherent states of light is used to perform the cryptographic service of data encryption. In this scheme a legitimate receiver, with use of a short, shared, secret‐key, executes a simple binary decision rule on every transmitted bit. An eavesdropper, on the other hand, who does not possess the secret‐key, is subjected to an irreducible quantum uncertainty in each measurement, even with the use of ideal detectors. We have implemented this scheme to demonstrate quantum‐noise‐protected data encryption at 650 Mbps through a 200 km, in‐line amplified, WDM line. The line simultaneously carried two 10 Gbps standard data channels, 100 GHz on either side of the encrypted channel, which shows that this scheme is compatible with the widely deployed WDM fiber‐optic infrastructure.

Eric Corndorf, Gregory S. Kanter, Chuang Liang +1 more

We demonstrate quantum-noise protected data encryption over a 2OOkm optically amplified WDM fiber line at 650Mbps rate using off-the-shelf components. This demonstration paves the way for widespread deployment of quantum cryptography in WDM networks.