Quantum interference by coherence transfer from spin to orbital angular momentum of photons (original) (raw)
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Quantum Information Transfer from Spin to Orbital Angular Momentum of Photons
Physical Review Letters, 2009
The optical "spin-orbit" coupling occurring in a suitably patterned nonuniform birefringent plate known as 'q-plate' allows entangling the polarization of a single photon with its orbital angular momentum (OAM). This process, in turn, can be exploited for building a bidirectional "spin-OAM interface", capable of transposing the quantum information from the spin to the OAM degree of freedom of photons and vice versa. Here, we experimentally demonstrate this process by singlephoton quantum tomographic analysis. Moreover, we show that two-photon quantum correlations such as those resulting from coalescence interference can be successfully transferred into the OAM degree of freedom.
Polarization control of single photon quantum orbital angular momentum states
Optics Express, 2009
The orbital angular momentum of photons, being defined in an infinitely dimensional discrete Hilbert space, offers a promising resource for high-dimensional quantum information protocols in quantum optics. The biggest obstacle to its wider use is presently represented by the limited set of tools available for its control and manipulation. Here, we introduce and test experimentally a series of simple optical schemes for the coherent transfer of quantum information from the polarization to the orbital angular momentum of single photons and vice versa. All our schemes exploit a newly developed optical device, the so-called "q-plate", which enables the manipulation of the photon orbital angular momentum driven by the polarization degree of freedom. By stacking several qplates in a suitable sequence, one can also access to higher-order angular momentum subspaces. In particular, we demonstrate the control of the orbital angular momentum m degree of freedom within the subspaces of |m| = 2h and |m| = 4h per photon. Our experiments prove that these schemes are reliable, efficient and have a high fidelity.
Journal of Optics, 2011
A few years ago the possibility of coupling and inter-converting the spin and orbital angular momentum (SAM and OAM) of paraxial light beams in inhomogeneous anisotropic media was demonstrated. An important case is provided by waveplates having a singular transverse pattern of the birefringent optical axis, with a topological singularity of charge q at the plate center, hence named 'q-plates'. The introduction of q-plates has given rise in recent years to a number of new results and to significant progress in the field of orbital angular momentum of light. Particularly promising are the quantum photonic applications, because the polarization control of OAM allows the transfer of quantum information from the SAM qubit space to an OAM subspace of a photon and vice versa. In this paper, we review the development of the q-plate idea and some of the most significant results that have originated from it, and we will briefly touch on many other related findings concerning the interaction of the SAM and OAM of light.
Deterministic qubit transfer between orbital and spin angular momentum of single photons
Optics Letters, 2012
In this work we experimentally implement a deterministic transfer of a generic qubit initially encoded in the orbital angular momentum of a single photon to its polarization. Such transfer of quantum information, completely reversible, has been implemented adopting a electrically tunable q-plate device and a Sagnac interferomenter with a Dove's prism. The adopted scheme exhibits a high fidelity and low losses.
Molecular Crystals and Liquid Crystals, 2012
The angular momentum of light can be split into a spin and an orbital component (SAM and OAM). A few years ago, an optical process involving a conversion of angular momentum from one form to the other was conceived and experimentally demonstrated in a singular patterned liquid crystal cell, also known as "q-plate". In this paper, after reviewing the q-plate concept and technology, we will survey some of the most significant results that have originated from it, with particular attention to the possibility of realizing a physical one-to-one mapping between the polarization Poincaré sphere and an OAM subspace of an optical beam or of a single photon.
High-Efficiency Detection of a Single Quantum of Angular Momentum by Suppression of Optical Pumping
Physical Review Letters, 2004
We propose and demonstrate experimentally the discrimination between two spin states of an atom purely on the basis of their angular momentum. The discrimination relies on angular momentum selection rules and does not require magnetic effects such as a magnetic dipole moment of the atom or an applied magnetic field. The central ingredient is to prevent by coherent population trapping an optical pumping process which would otherwise relax the spin state before a detectable signal could be obtained. We detected the presence or absence of a single quantum (1 h) of angular momentum in a trapped calcium ion in a single observation with success probability 0.86. As a practical technique, the method can be applied to read out some types of quantum computer.
On the Coupling of Photon Spin to Electron Orbital Angular Momentum
Partially gold coated 90° glass wedges and a semi-infinite slit in a thin film of gold ending in a conducting nano-junction serve as samples to investigate the transfer of photon spin to electron orbital angular momentum. These structures were specifically designed as samples where an incident beam of light is retroreflected. Since in the process of retroreflection the turning sense of a circularly polarized beam of light does not change and the direction of propagation is inverted, the photon spin is inverted. Due to conservation of angular momentum a transfer of photon spin to electron orbital angular momentum of conduction electrons occurs. In the structures a circular movement of electrons is blocked and therefore the transfered spin can be detected as a photovoltage due to an electromotive force which is induced by the transfer of angular momentum. Depending on the polarization of the incident beam, a maximum photovoltage of about 0,2µV was measured for both structures. The results are interpreted in terms of a classical electrodynamic model of the monochromatic linearly polarized photon as a propagating solitary electromagnetic wave of finite energy h which carries an angular momentum ℎ 2 which is elaborated elsewhere where h is Planck's constant and the frequency of light. The relative values of the measured photovoltages for different polarizations can well be explained by the electrodynamic model of a photon and an associated spin angular momentum. The absolute values of the measured photovoltages are also consistent with the interpretation. The observed effects are closely related to the lateral Fedorov Imbert shift of focused beams in optics and the optical spin Hall effect and to other non linear optical effects such as the inverse faraday effect for which a new interpretation is given here in terms of the electrodynamic model of the photon and its spin.
Physical Review Letters, 2004
We present a novel method for efficient sorting of photons prepared in states of orbital angular momentum (OAM) and angular position (ANG). A log-polar optical transform is used in combination with a holographic beam-splitting method to achieve better mode discrimination and reduced cross-talk than reported previously. Simulating this method for 7 modes, we have calculated an improved mutual information of 2.43 bits/photon and 2.29 bits/photon for OAM and ANG modes respectively. In addition, we present preliminary results from an experimental implementation of this technique. This method is expected to have important applications for high-dimensional quantum key distribution systems.
Photon orbital angular momentum: problems and perspectives
Fortschritte der Physik, 2004
The availability of laser beams carrying orbital angular momentum in addition to spin angular momentum paved the way to the observation of novel effects in quantum and classical optics. These effects are reviewed in this paper with emphasis on future perspectives.