Katherine Wagner

Entangling the Spatial Properties of Laser Beams

Position and momentum were the first pair of conjugate observables explicitly used to illustrate the intricacy of quantum mechanics. We have extended position and momentum entanglement to bright optical beams. Applications in optical metrology and interferometry require the continuous measurement of laser beams, with the accuracy fundamentally limited by the uncertainty principle. Techniques based on spatial entanglement of the beams could overcome this limit, and high-quality entanglement is required. We report a value of 0.51 for inseparability and 0.62 for the Einstein-Podolsky-Rosen criterion, both normalized to a classical limit of 1. These results are a conclusive optical demonstration of macroscopic position and momentum quantum entanglement and also confirm that the resources for spatial multimode protocols are available.

Observation of a comb of optical squeezing over many gigahertz of bandwidth

We experimentally measure optical squeezing at multiple longitudinal modes of an optical parametric amplifier. We present data up to 5.1 GHz that shows the magnitude of the squeezing is greater than observable at baseband.

Asymmetric EPR entanglement in continuous variable systems

Continuous variable entanglement can be produced in nonlinear systems or via the interference of squeezed states. In many optical systems such as parametric down conversion, the production of two perfectly symmetric subsystems is usually assumed when demonstrating the existence of entanglement. This symmetry simplifies the description of entanglement. However, asymmetry in entanglement may arise naturally in a real experiment, or be intentionally introduced in a given quantum information protocol. These asymmetries can emerge from having the output beams experience different losses and environmental contamination, or from the availability of non-identical input quantum states in quantum communication protocols. In this paper, we present a visualization of entanglement using quadrature amplitude plots of the twin beams. We quantitatively discuss the strength of asymmetric entanglement using EPR and inseparability criteria and theoretically show that the optimal beamsplitter ratio for entanglement is dependent on the asymmetries and may not be 50 : 50. To support this theory, we present experimental results showing one particular asymmetric entanglement where a 78 : 22 beamsplitter is optimal for observing entanglement.

Entangling spatial modes within a single beam

We combine experimental improvements to present an in principle demonstration of the use of multiple co propagating modes for quantum protocols.

Experimental realization of spatial entanglement for bright optical beams

The latest results on the experimental generation of the position and momentum (x-p) entanglement for bright optical beams are presented. The measurements of the quantum correlations in the TEM10 mode with two optical parametric amplifiers are demonstrated. TEM10 quadrature entanglement is also demonstrated. Two position squeezed beams on a 50:50 beam splitter are used to demonstrate full x-p entanglement.

Tools for Spatial Multimode Quantum Optics

The spatial properties of laser beams can be used to encode, transfer and detect quantum information into high order modes with high efficiency. We demonstrate the use of such states, including spatial squeezing and entanglement.