Valentina Parigi | LIP6 - Équipe QI

Spectrally multimode squeezed states generation at telecom wavelengths

Fri, 01 Nov 2024 00:00:00 +0000

We report on the experimental demonstration of a source that generates spectrally multimode squeezed states of light over the infrared C-Band. This is achieved using a single-pass Spontaneous Parametric Down Conversion (SPDC) process in a periodically-poled KTP waveguide that is pumped with the second harmonic of a femtosecond laser. Our measurements show significant squeezing in more than 21 frequency modes, with a maximum squeezing value over 2.5 dB. Moreover, we demonstrate multiparty entanglement across 8 individual frequency bands by measuring the covariance matrix of their quadratures. Finally, we use reconfigurable mode-selective homodyne detection to mold the output into cluster states of various shapes. This result paves the way for the implementation of continuous variable quantum information protocols at telecommunication wavelengths, with applications in multiparty, entanglement-based quantum communication and computation.

Cost and Routing of Continuous Variable Quantum Networks

Fri, 20 Oct 2023 00:00:00 +0000

We study continuous-variable graph states as quantum communication networks. We explore graphs with regular and complex network shapes distributed among different agents and we report for their cost as a global measure of squeezing and number of squeezed modes that are necessary to build the network. We show that the trend of the squeezing cost presents a non-trivial scaling with the size of the network strictly dependent on its topology. We devise a routing protocol based on local quadrature measurements for reshaping the network in order to perform teleportation protocol between two arbitrary nodes of the networks. The \textit{Routing} protocol, which is based on wire-shortening over parallel paths among the nodes, improves the final entanglement between the two nodes in a considerable amount of cases, and it is particularly efficient in running-time for complex sparse networks.

Mode-selective single-photon addition to a multimode quantum field

Sat, 01 Jan 2022 00:00:00 +0000

Spectro-temporal modes of light can be exploited for the generation of high-dimensional Gaussian quantum states. Such states are at the basis of continuous variable quantum information protocols where they have to support mode-selective non-Gaussian operations. We develop a general framework for single-photon addition on multimode states of light via parametric down conversion (PDC) processes. We identify the analytical conditions for single-mode and mode-selective photon addition. We show that spectral mode selectivity can be achieved in the type-II collinear down conversion, while single-mode condition are retrieved for noncollinear type-I and type-II processes. Numerical results are shown for photon addition in PDC process at near-infrared and telecommunications wavelengths.

Certification of Non-Gaussian States with Operational Measurements

Thu, 03 Jun 2021 00:00:00 +0000

We derive a theoretical framework for the experimental certification of non-Gaussian features of quantum states using double homodyne detection. We rank experimental non-Gaussian states according to the recently defined stellar hierarchy and we propose practical Wigner negativity witnesses. We simulate various use-cases ranging from fidelity estimation to witnessing Wigner negativity. Moreover, we extend results on the robustness of the stellar hierarchy of non-Gaussian states. Our results illustrate the usefulness of double homodyne detection as a practical measurement scheme for retrieving information about continuous-variable quantum states, and show that certification of high-order non-Gaussian features can be carried out experimentally with current technology.