arXiv subjects

Lorenzo Marrucci

Publications and source records attributed to Lorenzo Marrucci.

At least 73 records · Page 4Linked to original sources

arXiv2012

Time-division multiplexing of the orbital angular momentum of light

We present an optical setup for generating a sequence of light pulses in which the orbital angular momentum (OAM) degree of freedom is correlated with the temporal one. The setup is based on a single $q$-plate within a ring optical resonator. By this approach, we demonstrate the generation of a train of pulses carrying increasing values of OAM, or, alternatively, of a controlled temporal sequence of pulses having prescribed OAM superposition states. Finally, we exhibit an "OAM-to-time conversion" apparatus dividing different input OAM states into different time-bins. The latter application provides a simple approach to digital spiral spectroscopy of pulsed light.

physics.optics↗

arXiv2012

Spin-to-Orbital Angular Momentum Conversion and Spin-Polarization Filtering in Electron Beams

We propose the design of a space-variant Wien filter for electron beams that induces a spin half-turn and converts the corresponding spin angular momentum variation into orbital angular momentum of the beam itself by exploiting a geometrical phase arising in the spin manipulation. When applied to a spatially coherent input spin-polarized electron beam, such a device can generate an electron vortex beam, carrying orbital angular momentum. When applied to an unpolarized input beam, the proposed device, in combination with a suitable diffraction element, can act as a very effective spin-polarization filter. The same approach can also be applied to neutron or atom beams.

physics.atom-ph↗

arXiv2012

Laser-induced radial birefringence and spin-to-orbital optical angular momentum conversion in silver-doped glasses

Samples of Ag$^+$/Na$^{+}$ ion-exchanged glass that have been subject to intense laser irradiation may develop novel optical properties, as a consequence of the formation of patterns of silver nanoparticles and other structures. Here, we report the observation of a laser-induced permanent transverse birefringence, with the optical axis forming a radial pattern, as revealed by the spin-to-orbital angular momentum conversion occurring in a probe light beam. The birefringence pattern can be modeled well as resulting from thermally-induced stresses arising in the silver-doped glass during laser exposure, although the actual mechanism leading to the permanent anisotropy is probably more complex.

physics.optics↗

arXiv2012

Polarization pattern of vector vortex beams generated by $q$-plates with different topological charges

We describe the polarization topology of the vector beams emerging from a patterned birefringent liquid crystal plate with a topological charge $q$ at its center ($q$-plate). The polarization topological structures for different $q$-plates and different input polarization states have been studied experimentally by measuring the Stokes parameters point-by-point in the beam transverse plane. Furthermore, we used a tuned $q=1/2$-plate to generate cylindrical vector beams with radial or azimuthal polarizations, with the possibility of switching dynamically between these two cases by simply changing the linear polarization of the input beam.

physics.optics↗

arXiv2011

Deterministic qubit transfer between orbital and spin angular momentum of single photons

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.

quant-ph↗

arXiv2011

Resilience of orbital angular momentum qubits and effects on hybrid entanglement

The orbital angular momentum of light (OAM) provides a promising approach for the implementation of multidimensional states (qudits) for quantum information purposes. In order to characterize the degradation undergone by the information content of qubits encoded in a bidimensional subspace of the orbital angular momentum degree of freedom of photons, we study how the state fidelity is affected by a transverse obstruction placed along the propagation direction of the light beam. Emphasis is placed on the effects of planar and radial hard-edged aperture functions on the state fidelity of Laguerre-Gaussian transverse modes and the entanglement properties of polarization-OAM hybrid-entangled photon pairs.

quant-ph↗

arXiv2011

Spin-orbit hybrid entanglement of photons and quantum contextuality

We demonstrate electromagnetic quantum states of single photons and of correlated photon pairs exhibiting "hybrid" entanglement between spin and orbital angular momentum. These states are obtained from entangled photon pairs emitted by spontaneous parametric down conversion, by employing a $q$-plate for coupling the spin and orbital degrees of freedom of a photon. Entanglement and contextual quantum behavior (that is also non-local, in the case of photon pairs) is demonstrated by the reported violation of the Clauser-Horne-Shimony-Holt inequality. In addition a classical analog of the hybrid spin-orbit photonic entanglement is reported and discussed.

quant-ph↗

arXiv2010

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

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.

quant-ph↗

arXiv2010

Photon spin-to-orbital angular momentum conversion via an electrically tunable $q$-plate

Exploiting electro-optic effects in liquid crystals, we achieved real-time control of the retardation of liquid- crystal-based $q$-plates through an externally applied voltage. The newly conceived electro-optic $q$-plates can be operated as electrically driven converters of photon spin into orbital angular momentum, enabling a variation of the orbital angular momentum probabilities of the output photons over a time scale of milliseconds.

physics.optics↗

arXiv2010

Experimental generation and characterization of single-photon hybrid ququarts based on polarization-orbital angular momentum encoding

High-dimensional quantum states, or qudits, represent a promising resource in the quantum information field. Here we present the experimental generation of four-dimensional quantum states, or ququarts, encoded in the polarization and orbital angular momentum of a single photon. Our novel technique, based on the q-plate device, allows to prepare and measure the ququart in all five mutually unbiased bases. We report the reconstruction of the four dimensional density matrix through the tomographic procedure for different ququart states.

quant-ph↗

arXiv2010

Experimental optimal cloning of four-dimensional quantum states of photons

Optimal quantum cloning is the process of making one or more copies of an arbitrary unknown input quantum state with the highest possible fidelity. All reported demonstrations of quantum cloning have so far been limited to copying two-dimensional quantum states, or qubits. We report the experimental realization of the optimal quantum cloning of four-dimensional quantum states, or ququarts, encoded in the polarization and orbital angular momentum degrees of freedom of photons. Our procedure, based on the symmetrization method, is also shown to be generally applicable to quantum states of arbitrarily high dimension -- or qudits -- and to be scalable to an arbitrary number of copies, in all cases remaining optimal. Furthermore, we report the bosonic coalescence of two single-particle entangled states.

quant-ph↗

arXiv2010

Polarization-controlled evolution of light transverse modes and associated Pancharatnam geometric phase in orbital angular momentum

We present an easy, efficient and fast method to generate arbitrary linear combinations of light orbital angular momentum eigenstates $\ell=\pm 2$ starting from a linearly polarized TEM$_{00}$ laser beam. The method exploits the spin-to-orbital angular momentum conversion capability of a liquid-crystal-based $q$-plate and a Dove prism inserted in a Sagnac polarizing interferometer. The nominal generation efficiency is 100\%, being limited only by reflection and scattering losses in the optical components. When closed paths are followed on the polarization Poincaré sphere of the input beam, the associated Pancharatnam geometric phase is transferred unchanged to the orbital angular momentum state of the output beam.

physics.optics↗

arXiv2010

Efficient generation and control of different order orbital angular momentum states for communication links

We present a novel optical device to encode and decode two bits of information into different Orbital Angular Momentum (OAM) states of a paraxial optical beam. Our device generates the four angular momentum states of order $\pm 2$ and $\pm4$ by Spin-To-Orbital angular momentum Conversion (STOC) in a triangular optical loop arrangement. The switching among the four OAM states is obtained by changing the polarization state of the circulating beam by two quarter wave plates and the two-bit information is transferred to the beam OAM exploiting a single $q$-plate. The polarization of the exit beam is left free for additional one bit of information. The transmission bandwidth of the device may be as large as several megahertz if electro-optical switches are used to change the beam polarization. This may be particularly useful in communication system based on light OAM.

physics.optics↗

arXiv2009

Universal unitary gate for single-photon spinorbit four-dimensional states

The recently demonstrated possibility of entangling opposite values of the orbital angular momentum (OAM) of a photon with its spin enables the realization of nontrivial one-photon spinorbit four-dimensional states for quantum information purposes. Hitherto, however, an optical device able to perform arbitrary unitary transformations on such spinorbit photon states has not been proposed yet. In this work we show how to realize such a ``universal unitary gate'' device, based only on existing optical technology, and describe its operation. Besides the quantum information field, the proposed device may find applications wherever an efficient and convenient manipulation of the combined OAM and spin of light is required.

quant-ph↗

arXiv2009

Quantum information transfer from spin to orbital angular momentum of photons

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 \textit{vice versa}. Here, we experimentally demonstrate this process by single-photon 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.

quant-ph↗

arXiv2009

Efficient generation and sorting of orbital angular momentum eigenmodes of light by thermally tuned q-plates

We present methods for generating and for sorting specific orbital angular momentum (OAM) eigenmodes of a light beam with high efficiency, using a liquid crystal birefringent plate with unit topological charge, known as \qo{q-plate}. The generation efficiency has been optimized by tuning the optical retardation of the q-plate with temperature. The measured OAM $m=\pm2$ eigenmodes generation efficiency from an input TEM$_{00}$ beam was of 97%. Mode sorting of the two input OAM $m=\pm2$ eigenmodes was achieved with an efficiency of 81% and an extinction-ratio (or cross-talk) larger than 4.5:1.

physics.optics↗

arXiv2009

Improved focusing with Hypergeometric-Gaussian type-II optical modes

We present a novel family of paraxial optical beams having a confluent hypergeometric transverse profile, which we name hypergeometric Gauss modes of type-II (HyGG-II). These modes are eigenmodes of the photon orbital angular momentum and they have the lowest beam divergence at waist of HyGG-II among all known finite power families of paraxial modes. We propose to exploit this feature of HyGG-II modes for generating, after suitable focusing, a "light needle" having record properties in terms of size and aspect ratio, possibly useful for near-field optics applications.

physics.optics↗

arXiv2009

Light propagation in a birefringent plates with topological charge

We calculated the Fresnel paraxial propagator in a birefringent plate having topological charge $q$ at its center, named "$q$-plate". We studied the change of the beam transverse profile when it traverses the plate. An analytical closed form of the beam profile propagating in the "$q$-plate" can be found for many important specific input beam profiles. We paid particular attention to the plate having a topological unit charge and we found that if small losses due to reflection, absorption and scattering are neglected, the plate can convert the photon spin into orbital angular momentum with up to 100% efficiency, provided the thickness of the plate is less than the Rayleigh range of the incident beam.

physics.optics↗