Light pulses and perfect light sources

L. C. Comandar, Marco Lucamarini, B. Fröhlich +3 more

We drastically improve the mode overlap between independently seeded, gain-switched laser diodes operating at gigahertz repetition rates by implementing a pulsed light seeding technique. Injecting pulsed light reduces the emission time jitter and enables frequency chirp synchronization while maintaining random optical phases of the emitted laser pulses. We measure interference of these pulsed sources both in the macroscopic regime, where we demonstrate near perfect mode overlap, and in the single photon regime, where we achieve a Hong-Ou-Mandel dip visibility of 0.499 ± 0.004, thus saturating the theoretical limit of 0.5. The measurement results are reproduced by Monte-Carlo simulations with no free parameters. Our light source is an ideal solution for generation of high rate, indistinguishable coherent pulses for quantum information applications.

Andy Francis

Benoît Darquié, M. P. A. Jones, J. Dingjan +6 more

By illuminating an individual rubidium atom stored in a tight optical tweezer with short resonant light pulses, we created an efficient triggered source of single photons with a well-defined polarization. The measured intensity correlation of the emitted light pulses exhibits almost perfect antibunching. Such a source of high-rate, fully controlled single-photon pulses has many potential applications for quantum information processing.

Salvatore Carusotto

A. M. Akulshin, Peter Hannaford, Russell McLean +1 more

Ding Liang-En

The single-photon sources used in most of the practical QKD systems are obtained through attenuating the weak laser pulse.It is not a perfect single-photon source,but is a quasisingle-photon source which follows the Poissonian distribution.The probability of every nonempty light pulse containing multiphoton is nonzero,the powerful eavesdropper(Eve) can take advantage of this to obtain some information about the final key.So it is necessary to study the security of the practical QKD system.Supposing,Eve launches photon-number-splitting(PNS) attack on multiphoton signals,and optimal attack(OA) on single-photon signals,adopting Shannon′s information theory to analyze the security of the practical QKD system based on weak coherent light.The result shows that the practical QKD system is secure against the attacks of PNS and OA,and the upper bound of the error rate that the legitimate users(Alice and Bob) can tolerate is also derived from are study.