Continuous-variable entangled states of light carrying orbital angular momentum

Abstract

The orbital angular momentum of light, unlike spin, is an infinite-dimensional discrete variable and may hence offer enhanced performances for encoding, transmitting, and processing quantum information. Hitherto, this degree of freedom of light has been studied mainly in the context of quantum states with definite number of photons. On the other hand, field-quadrature continuous-variable quantum states of light allow implementing many important quantum protocols not accessible with photon-number states. Here, we realize a novel scheme based on a q-plate device for endowing a bipartite continuous-variable Gaussian entangled state with non-zero orbital angular momentum. We then apply a reconfigurable homodyne detector working directly with such non-zero orbital angular momentum modes in order to retrieve experimentally their entire quantum-state covariance matrix, thus providing a full characterisation of their quantum fluctuation properties. Our work is a step towards generating multipartite continuous-variable entanglement in a single optical beam.PACS numbers: 03.67.Bg Entanglement production and manipulation; 42.50.Tx Optical angular momentum and its quantum aspects; 42.50.Dv Quantum state engineering and measurements;

Generalized Orbital Angular Momentum Symmetry in Parametric Amplification

“…In particular, OAM conservation and intensity overlap between the down-converted beams were shown to impose a reflection symmetry in the Poincaré sphere representaion of the signal and idler beams [32][33][34][35]. OAM correlations inside an OPO give rise to entanglement in the continuous variable regime [36], that can be combined with polarization to produce continuous variable hyperentanglement [37][38][39][40][41].…”

Entangled photon assisted multidimensional nonlinear optics of exciton–polaritons

“…Depending on their generation processes, the photonic modes can be entangled in temporal-spectral, polarization, or the orbital angular momentum degrees of freedom. [11][12][13] For the pump-probe analog proposed in this communication, we focus on the biphoton sources having non-classical spectral-temporal properties in the optical regime.…”

Spatiotemproal effects on squeezing measurements

“…The Laguerre-Gauss modal basis is an example of an orbital angular momentum (OAM) basis. Recently, the incorporation of OAM modes into squeezed states has attracted much attention [17,[27][28][29][30]. Our interest is to determine the effect of the azimuthal index (OAM) on homodyning measurements.…”