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Dive into the research topics where G. Lima is active.

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Featured researches published by G. Lima.


Optics Express | 2011

Experimental quantum tomography of photonic qudits via mutually unbiased basis.

G. Lima; L. Neves; R. Guzmán; Esteban S. Gómez; W. A. T. Nogueira; A. Delgado; Asticio Vargas; C. Saavedra

We present the experimental quantum tomography of 7- and 8-dimensional quantum systems based on projective measurements in the mutually unbiased basis (MUB-QT). One of the advantages of MUB-QT is that it requires projections from a minimal number of bases to be performed. In our scheme, the higher dimensional quantum systems are encoded using the propagation modes of single photons, and we take advantage of the capabilities of amplitude- and phase-modulation of programmable spatial light modulators to implement the MUB-QT.


Scientific Reports | 2013

Quantum key distribution session with 16-dimensional photonic states

Sebastián Etcheverry; G. Cañas; E. S. Gómez; W. A. T. Nogueira; C. Saavedra; G. B. Xavier; G. Lima

The secure transfer of information is an important problem in modern telecommunications. Quantum key distribution (QKD) provides a solution to this problem by using individual quantum systems to generate correlated bits between remote parties, that can be used to extract a secret key. QKD with D-dimensional quantum channels provides security advantages that grow with increasing D. However, the vast majority of QKD implementations has been restricted to two dimensions. Here we demonstrate the feasibility of using higher dimensions for real-world quantum cryptography by performing, for the first time, a fully automated QKD session based on the BB84 protocol with 16-dimensional quantum states. Information is encoded in the single-photon transverse momentum and the required states are dynamically generated with programmable spatial light modulators. Our setup paves the way for future developments in the field of experimental high-dimensional QKD.


Optics Express | 2009

Manipulating spatial qudit states with programmable optical devices

G. Lima; Asticio Vargas; L. Neves; R. Guzmán; C. Saavedra

The study of how to generate high-dimensional quantum states (qudits) is justified by the advantages that they can bring for the field of quantum information. However, to have some real practical potential for quantum communication, these states must be also of simple manipulation. Spatial qudits states, which are generated by engineering the transverse momentum of the parametric down-converted photons, have been until now considered of hard manipulation. Nevertheless, we show in this work a simple technique for modifying these states. This technique is based on the use of programmable diffractive optical devices, that can act as spatial light modulators, to define the Hilbert space of these photons instead of pre-fabricated multi-slits.


Physical Review A | 2009

Hybrid photonic entanglement: Realization, characterization and applications

Leonardo Neves; G. Lima; A. Delgado; C. Saavedra

We show that the quantum disentanglement eraser implemented on a two-photon system from parametric downconversion is a general method to create hybrid photonic entanglement, namely the entanglement between different degrees of freedom of the photon pair. To demonstrate this, we generate and characterize a source with tunable degree of hybrid entanglement between two qubits, one encoded in the transverse momentum and position of a photon, and the other in the polarization of its partner. In addition, we show that a simple extension of our setup enables the generation of two-photon qubit-qudit hybrid entangled states. Finally, we discuss the advantages that this type of entanglement can bring for an optical quantum network.


Nature Communications | 2013

Long-distance distribution of genuine energy-time entanglement

Álvaro Cuevas; Gonzalo Carvacho; G. Saavedra; Jaime Cariñe; W. A. T. Nogueira; Miguel Figueroa; Adan Cabello; Paolo Mataloni; G. Lima; Guilherme B. Xavier

Any practical realization of entanglement-based quantum communication must be intrinsically secure and able to span long distances avoiding the need of a straight line between the communicating parties. The violation of Bell’s inequality offers a method for the certification of quantum links without knowing the inner workings of the devices. Energy-time entanglement quantum communication satisfies all these requirements. However, currently there is a fundamental obstacle with the standard configuration adopted: an intrinsic geometrical loophole that can be exploited to break the security of the communication, in addition to other loopholes. Here we show the first experimental Bell violation with energy-time entanglement distributed over 1 km of optical fibres that is free of this geometrical loophole. This is achieved by adopting a new experimental design, and by using an actively stabilized fibre-based long interferometer. Our results represent an important step towards long-distance secure quantum communication in optical fibres.


Physical Review Letters | 2015

Five Measurement Bases Determine Pure Quantum States on Any Dimension.

D. Goyeneche; Gustavo Cañas; Sebastián Etcheverry; Esteban S. Gómez; Guilherme B. Xavier; G. Lima; A. Delgado

A long-standing problem in quantum mechanics is the minimum number of observables required for the characterization of unknown pure quantum states. The solution to this problem is especially important for the developing field of high-dimensional quantum information processing. In this work we demonstrate that any pure d-dimensional state is unambiguously reconstructed by measuring five observables, that is, via projective measurements onto the states of five orthonormal bases. Thus, in our method the total number of different measurement outcomes (5d) scales linearly with d. The state reconstruction is robust against experimental errors and requires simple postprocessing, regardless of d. We experimentally demonstrate the feasibility of our scheme through the reconstruction of eight-dimensional quantum states, encoded in the momentum of single photons.


Physical Review Letters | 2014

Applying the Simplest Kochen-Specker Set for Quantum Information Processing

Gustavo Cañas; Mauricio Aguayo Arias; Sebastián Etcheverry; Esteban S. Gómez; Adan Cabello; Guilherme B. Xavier; G. Lima

Kochen-Specker (KS) sets are key tools for proving some fundamental results in quantum theory and also have potential applications in quantum information processing. However, so far, their intrinsic complexity has prevented experimentalists from using them for any application. The KS set requiring the smallest number of contexts has been recently found. Relying on this simple KS set, here we report an input state-independent experimental technique to certify whether a set of measurements is actually accessing a preestablished quantum six-dimensional space encoded in the transverse momentum of single photons.


Physical Review A | 2010

Experimental Bell-inequality violation without the postselection loophole

G. Lima; Giuseppe Vallone; Andrea Chiuri; Adan Cabello; Paolo Mataloni

We report on an experimental violation of the Bell-Clauser-Horne-Shimony-Holt (Bell-CHSH) inequality using energy-time-entangled photons. The experiment is not free of the locality and detection loopholes but is the first violation of the Bell-CHSH inequality using energy-time entangled photons which is free of the postselection loophole described by Aerts et al. [Phys. Rev. Lett. 83, 2872 (1999)].


Physical Review A | 2017

High-dimensional decoy-state quantum key distribution over multicore telecommunication fibers

Gustavo Cañas; N. Vera; J. Cariñe; P. González; J. Cardenas; P. W. R. Connolly; A. Przysiezna; Esteban S. Gómez; M. Figueroa; Giuseppe Vallone; P. Villoresi; T. Ferreira da Silva; Guilherme B. Xavier; G. Lima

Author(s): Canas, G; Vera, N; Carine, J; Gonzalez, P; Cardenas, J; Connolly, PWR; Przysiezna, A; Gomez, ES; Figueroa, M; Vallone, G; Villoresi, P; da Silva, T Ferreira; Xavier, GB; Lima, G | Abstract: Multiplexing is a strategy to augment the transmission capacity of a communication system. It consists of combining multiple signals over the same data channel and it has been very successful in classical communications. However, the use of enhanced channels has only reached limited practicality in quantum communications (QC) as it requires the complex manipulation of quantum systems of higher dimensions. Considerable effort is being made towards QC using high-dimensional quantum systems encoded into the transverse momentum of single photons but, so far, no approach has been proven to be fully compatible with the existing telecommunication infrastructure. Here, we overcome such a technological challenge and demonstrate a stable and secure high-dimensional decoy-state quantum key distribution session over a 0.3 km long multicore optical fiber. The high-dimensional quantum states are defined in terms of the multiple core modes available for the photon transmission over the fiber, and the decoy-state analysis demonstrates that our technique enables a positive secret key generation rate up to 25 km of fiber propagation. Finally, we show how our results build up towards a high-dimensional quantum network composed of free-space and fiber based links


Physical Review A | 2014

Experimental implementation of an eight-dimensional Kochen-Specker set and observation of its connection with the Greenberger-Horne-Zeilinger theorem

Gustavo Cañas; Sebastián Etcheverry; Esteban S. Gómez; C. Saavedra; Guilherme B. Xavier; G. Lima; Adan Cabello

For eight-dimensional quantum systems there is a Kochen-Specker (KS) set of 40 quantum yes-no tests that is related to the Greenberger-Horne-Zeilinger (GHZ) proof of Bells theorem. Here we experimentally implement this KS set using an eight-dimensional Hilbert space spanned by the transverse momentum of single photons. We show that the experimental results of these tests violate a state-independent noncontextuality inequality. In addition, we show that, if the system is prepared in states that are formally equivalent to a three-qubit GHZ and

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S. Pádua

Universidade Federal de Minas Gerais

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Paolo Mataloni

Sapienza University of Rome

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Fabio Sciarrino

Sapienza University of Rome

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Leonardo Neves

Universidade Federal de Minas Gerais

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C. H. Monken

Universidade Federal de Minas Gerais

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