Anh Tuan Nguyen

Frequency Bin Entangled Photons

A monochromatic laser pumping a parametric down-conversion crystal generates frequency-entangled photon pairs. We study this experimentally by addressing such frequency-entangled photons at telecommunication wavelengths (around 1550 nm) with fiber-optics components such as electro-optic phase modulators and narrow-band frequency filters. The theory underlying our approach uses the notion of frequency-bin entanglement. Our results show that the phase modulators address coherently up to eleven frequency bins, leading to an interference pattern which can violate by more than five standard deviations a Bell inequality adapted to our setup.

Photon pair source based on parametric fluorescence in periodically poled twin-hole silica fiber

We present observations of quasi-phase matched parametric fluorescence in a periodically poled twin-hole silica fiber. The phase matching condition in the fiber enables the generation of a degenerate signal field in the fiber-optic communication band centered on 1556 nm. We performed coincidence measurements and a Hong-Ou-Mandel experiment to validate that the signal arises from photon pairs. A coincidence peak with a signal to noise ratio (SNR) of 4 using 43 mW of pump power and a Hong-Ou-Mandel dip showing 40% net visibility were measured. Moreover, the experiments were performed with standard single mode fibers spliced at both ends of the poled section, which makes this source easy to integrate in fiber-optic quantum communication applications.

Experimental quantum tossing of a single coin

The cryptographic protocol of coin tossing consists of two parties, Alice and Bob, who do not trust each other, but want to generate a random bit. If the parties use a classical communication channel and have unlimited computational resources, one of them can always cheat perfectly. If the parties use a quantum communication channel, there exist protocols such that neither party can cheat perfectly, although they may be able to significantly bias the coin. Here, we analyze in detail how the performance of a quantum coin tossing experiment should be compared to classical protocols, taking into account the inevitable experimental imperfections. We then report an all-optical fiber experiment in which a single coin is tossed whose randomness is higher than achievable by any classical protocol and present some easily realizable cheating strategies by Alice and Bob.

Enhanced cross phase modulation instability in birefringent photonic crystal fibers in the anomalous dispersion regime

We study Cross Phase Modulational Instability (CPMI) -a particular form of vector modulational instability- in the anomalous dispersion regime in highly birefringent, strongly dispersive optical fibers. When the pump power is high, the detuning of the Scalar Modulational Instability (SMI) is comparable to the detuning of the CPMI. The gain of the CPMI -which is usually much smaller than the gain of the SMI-, is then strongly enhanced and becomes much larger than the gain of the SMI. This theoretical prediction is well verified experimentally using small core photonic crystal fibers.

Manipulating frequency entanglement with phase modulators

A parametric down conversion source pumped by a monochromatic laser will produce frequency entangled photon pairs. We demonstrate this by an experiment in which five-dimensional frequency entanglement is manipulated at telecommunication wavelengths using commercially available components such as electro-optic phase modulators and narrowband frequency filters. A theoretical intuition for this approach is developed by introducing the notion of frequency bin entanglement. We conclude by showing that using this method one can in principle violate the CHSH, the CGLMP, and a new – as yet unnamed – Bell inequalities.

Manipulating Frequency Entangled Photons

A parametric down conversion source pumped by a monochromatic laser will produce frequency entangled photon pairs. We demonstrate this by an experiment in which five-dimensional frequency entanglement is manipulated at telecommunication wavelengths using commercially available components such as electro-optic phase modulators and narrowband frequency filters. A theoretical intuition for this approach is developed by introducing the notion of frequency bin entanglement. We conclude by showing that using this method one can in principle violate the CHSH, the CGLMP, and a new – as yet unnamed – Bell inequalities.

Fiber optics implementation of single quantum coin tossing

We report an all fiber optics experimental implementation of quantum coin tossing using attenuated laser pulses at 1550 nm in which a single coin is tossed whose randomness is higher than achievable by any classical protocol.

Photon pair source based on periodically poled twin-hole silica fibre

In this paper we report the experimental observation of photon pair generation in periodically poled twin-hole silica fibre. Compared with periodically poled D-shape fibres, twin-hole fibres have important advantages: direct splicing to standard fibres is possible; as well as periodic poling technology compatible with tens of centimetres of interaction length, thus potentially ensuring higher conversion.