Optimal quantum cloning of orbital angular momentum photon qubits via Hong-Ou-Mandel coalescence

TL;DR

This paper demonstrates optimal quantum cloning of orbital angular momentum photon qubits using Hong-Ou-Mandel coalescence, enabling scalable high-dimensional quantum information processing with OAM states.

Contribution

It introduces a method for quantum cloning of OAM qubits via Hong-Ou-Mandel interference, leveraging spin-OAM transfer and symmetrization techniques.

Findings

First observation of Hong-Ou-Mandel coalescence with OAM photons

Achieved universal optimal quantum cloning of OAM qubits

Scalable to high-dimensional quantum spaces and multiple degrees of freedom

Abstract

The orbital angular momentum (OAM) of light, associated with a helical structure of the wavefunction, has a great potential for quantum photonics, as it allows attaching a higher dimensional quantum space to each photon. Hitherto, however, the use of OAM has been hindered by its difficult manipulation. Here, exploiting the recently demonstrated spin-OAM information transfer tools, we report the first observation of the Hong-Ou-Mandel coalescence of two incoming photons having nonzero OAM into the same outgoing mode of a beam-splitter. The coalescence can be switched on and off by varying the input OAM state of the photons. Such effect has been then exploited to carry out the 1 \rightarrow 2 universal optimal quantum cloning of OAM-encoded qubits, using the symmetrization technique already developed for polarization. These results are finally shown to be scalable to quantum spaces of arbitrary dimension, even combining different degrees of freedom of the photons.