An efficient source of continuous variable polarization entanglement

Abstract

We have experimentally demonstrated the efficient creation of highly entangled bipartite continuous variable polarisation states. Exploiting an optimised scheme for the production of squeezing using the Kerr non-linearity of a glass fibre we generated polarisation squeezed pulses with a mean classical excitation inŜ 3 . Polarisation entanglement was generated by interfering two independent polarisation squeezed fields on a symmetric beam splitter. The resultant beams exhibit strong quantum noise correlations in the darkŜ 1 −Ŝ 2 polarisation plane. To verify entanglement generation, we characterised the quantum correlations of the system for two different sets of conjugate Stokes parameters. The quantum correlations along the squeezed and the anti-squeezed Stokes parameters were observed to be -4.1±0.3 dB and -2.6±0.3 dB below the shot noise level respectively. The degree of correlations was found to depend critically on the beam splitting ratio of the entangling beam splitter. Carrying out measurements on a different set of conjugate Stokes parameters, correlations of -3.6±0.3 dB and -3.4±0.3 dB have been observed. This result is more robust against asymmetries in the entangling beam splitter, even in the presence of excess noise.

Quantum correlations in separable multi-mode states and in classically entangled light

“…In the final step, mode C interferes with mode B on another balanced beam splitter and this activates entanglement between modes A and B verified by the sufficient condition for entanglement [54,55]:…”

“…Here g is a variable gain factor and variances ∆ 2 norm (.) are normalized to the respective mean values of Ŝ 3 (the bright polarization component), which corresponds to the shot noise reference (see, e.g., [55]). Note that the effective quadrature operators in Eq.…”

Entangling the Spatial Properties of Laser Beams

“…For some years after its proposal, the existence or otherwise of entanglement was seen as a fairly academic distinction, since at that stage there were no measures that could Introduction of the beams. There is now a vast array of hterature detaihng entanglement experiments that have been conducted with single mode continuous (cw) beams, with demonstrations of strong entanglement between the amplitude and phase quadratures of pairs of beams [5,6,7] or the polarisation of the beams [8,9,10].…”

Controlled Photon Switch Assisted by Coupled Quantum Dots

“…In comparison to these results using one degree of freedom (DOF) 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 , an extensive amount of researches have focused on generating entanglement in one degree of freedom (DOF), such as the quadrature 34 , polarization 35 36 or spatial field variables 37 38 . With these states even the generations of multimode entangled beams are possible, which may potentially simplify quantum communication systems, especially if multiple modes are contained within a single beam 39 .…”