Amplitude damping of Laguerre-Gaussian modes

Abstract

We present an amplitude damping channel for Laguerre-Gaussian modes. Our channel is tested experimentally for a Laguerre-Gaussian mode, having an azimuthal index l = 1, illustrating that it decays to a Gaussian mode in good agreement with the theoretical model for amplitude damping. Since we are able to characterize the action of such a channel on orbital angular momentum states, we propose using it to investigate the dynamics of entanglement.

Measurement of light's orbital angular momentum

“…However, the use of many cascaded interferometers is technically challenging. The use of just the first stage, the odd-from-even sorter, interferometer has been applied to demonstrate amplitude damping [31] and in the development of a linear optical CNOT gate for OAM [28]. The interferometric approach offers many advantages where the non-destructive sorting of OAM is required, such as a logic gate within Quantum Computing.…”

“…It should be noted that this chapter is not a complete treatise on the techniques that have been developed for the measurement of OAM. Methods converting OAM into SAM through the use qplates, Principal Component Analysis, and decomposition of beams carrying OAM into basis set of Bessel beams, among others have had varying success resolving the issues surrounding the measurement of OAM [49,89,26,69,31]. An ideal solution is the development of the equivalent of a polarising beam splitter for OAM, giving 100% detection efficiency at the single photon level.…”

“…Preserving the spatial structure of the input beam is important for many experiments, for example to demonstrate amplitude damping of Laguerre-Gaussian laser modes [31] and in the development of a linear optical CNOT gate for OAM [72,28].…”

On the quantum-channel capacity for orbital angular momentum-based free-space optical communications

“…The transmitted information rate over the atmospheric turbulence channels can be estimated by developing the transition model of OAM states of individual photons [1,2]. An analytical model describing the transition probabilities among OAM eigenkets propagated over the slant path atmospheric turbulence has been introduced in [3], while the amplitude damping model for the depolarizing quantum channel is discussed with respect to OAM states [4] and channel measurements [5].…”

“…The transition probability from an OAM quantum state jmi to OAM eigenket jni, after propagation through the free-space atmospheric turbulence, is derived in [2,4] as…”