Quantum State from Parametric Down-Conversion

Shan Gao

Yen-Ju Chen, Chun-Yuan Cheng, Tien-Dat Pham +4 more

Quantum fluctuation plays a key role in the parametric down-conversion in the Langevin regime. In this paper, we report the experimental realization of optical parametric down-conversion in the Langevin regime on a chip. By precisely controlling the loss inherently tied to fluctuation, we observe the asymmetric Hong-Ou-Mandel dip - a hallmark of quantum fluctuation in the fluctuation-driven PDC, and the fluctuation-induced compression of single photons by nearly one order of magnitude. These findings pave the way for the manipulation of quantum fluctuation, quantum states, and system-reservoir interaction.

Alessio Avella

Parametric Down Conversion (PDC) is a very important resource for what concern the development of quantum technologies and for experiments about foundation of quantum mechanics. The interest about this phenomenon is due to the fact that photons emitted by PDC are quantum correlated in many parameters and it is possible to use the PDC to produce states of light with strong non-classical behaviour. The aim of this paper is provide an extensive review on the theory of Parametric Down Conversion whit particular emphasis for what concern the case of Spontaneous Parametric Down Conversion (SPDC) in bulk non-linear crystals.

M. Bertolotti, Fabio Antonio Bovino, Concita Sibilia

Xiongfeng Ma, Chi‐Hang Fred Fung, Hoi‐Kwong Lo

In this paper, we show that decoy states are very simple to implement for quantum key distribution (QKD) with parametric down conversion (PDC) sources. Indeed, with no modification in the hardware at all, by using the AYKI scheme, one can achieve a key generation rate that is close to the theoretical limit of infinite decoy states. Therefore, we expect decoy state QKD to become a standard technique not only in the coherent state QKD, but also in QKD with PDC sources.