Nicolas Treps | 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.

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.

Detecting a target with quantum entanglement

Mon, 20 Dec 2021 00:00:00 +0000

In the last decade a lot of research activity focused on the use of quantum entanglement as a resource for remote target detection, i.e. on the design of a quantum radar. The literature on this subject uses tools of quantum optics and quantum information theory, and therefore often results obscure to radar scientists. This review has been written with purpose of removing this obscurity. As such, it contains a review of the main advances in the quantum radar literature together accompanied by a thorough introduction of the quantum optics background necessary for its understanding.

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.

Full characterization of the transmission properties of a multi-plane light converter

Fri, 01 Jan 2021 00:00:00 +0000

Multi-plane light conversion allows to perform arbitrary transformations on a finite set of spatial modes with no theoretical restriction to the quality of the transformation. Even though the number of shaped modes is in general small, the number of modes transmitted by a multi-plane light converter (MPLC) is extremely large. In this work, we aim to characterize the transmission properties of a multi-plane light converter inside and, for the first time, outside the design-modes subspace. By numerically reconstructing the transmission matrix of such systems, we individuate new ways to evaluate their efficiency in performing the design transformation. Moreover, we develop an analytical random matrix model that suggests that in the regime of a large number of shaped modes an MPLC behaves like a random scattering medium with limited number of controlled channels.

Violating Bell inequalities with entangled optical frequency combs and multi-pixel homodyne detection

Mon, 01 Jan 2018 00:00:00 +0000

We have theoretically investigated the possibility of using any of several continuous-variable Bell-type inequalities - for which the dichotomic measurements are achieved with coarse-grained quadrature (homodyne) measurements - in a multi-party configuration where each participant is given a section, in the frequency domain, of the output of an optical parametric oscillator which has been synchronously-pumped with a frequency comb. Such light sources are undergoing intense study due to their novel properties, including the potential for production of light entangled in many hundreds of physical modes - a critical component for many proposals in optical or hybrid-optical quantum computation proposals. The situation we study notably uses only highly-efficient optical homodyne detection, meaning that in such systems the fair-sampling loophole would be relatively easy to avoid.