Experimental characterization of continuous-variable orbital angular momentum entanglement using Stokes-operator basis

Abstract

The continuous-variable (CV) orbital angular momentum (OAM) entanglement is very different to the traditional quadrature entanglement. The Stokes-operators directly reflect the character of OAM light. Here, we report the first direct experimental demonstration the Stokes-operator entanglement of continuous-variable OAM entanglement. Generated by transforming quadrature entanglement in the HG mode onto the orbital Stokes-operator basis, the entanglement is measured in the Stokes-operator basis using a self-designed detection scheme. An inseparability of I(O^,O^)<1 is achieved over a wide analyzing frequency of 1-10 MHz. Moreover, experimental fluctuations at 5.0 MHz are visualized using the quantum orbital Poincaré sphere representation. The OAM entanglement with Stokes-operators measurement has a promising application in certain nonlocal quantum information protocols and rotational optomechanics by interacting with nanoparticle or atoms.

Generalized Orbital Angular Momentum Symmetry in Parametric Amplification

“…However, this effect can be compensated for with a two-crystal setup, as the one used in Ref. [38,39]. Active control of signal and idler spatial structures exploring symmetry conditions can be useful for shaping spatial quantum correlations generated 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].…”

Gouy-phase effects in the frequency combs of an optical parametric oscillator

“…More recently, different schemes using the OPO for the generation of multipartite entanglement have been successfully implemented. In the spatial domain, for example, an OPO pumped with structured light was shown to produce quadripartite entanglement between transverse modes of the downconverted fields [5,6]. In the spectral domain, a dual-frequency pump was used to entangle 60 modes in the quantum optical frequency comb of a single OPO [7].…”