Lamas Linares,Antia
Email Address
phylla@nus.edu.sg
30 results
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Publication Experimental falsification of leggett's nonlocal variable model(2007-11-21) Branciard, C.; Ling, A.; Gisin, N.; Kurtsiefer, C.; Lamas-Linares, A.; Scarani, V.; TEMASEK LABORATORIES; PHYSICSBell's theorem guarantees that no model based on local variables can reproduce quantum correlations. Also, some models based on nonlocal variables, if subject to apparently "reasonable" constraints, may fail to reproduce quantum physics. In this Letter, we introduce a family of inequalities, which use a finite number of measurement settings, and which therefore allow testing Leggett's nonlocal model versus quantum physics. Our experimental data falsify Leggett's model and are in agreement with quantum predictions. © 2007 The American Physical Society.Publication An optimal photon counting polarimeter(2006-07-10) Ling, A.; Soh, K.P.; Lamas-Linares, A.; Kurtsiefer, C.; TEMASEK LABORATORIES; PHYSICSWe present the experimental results for a method used to perform polarimetry on ensembles of single photons. Our setup is based on a measurement method known to be optimal for estimating the state of two-level systems. The setup has no moving parts and is sensitive to weak sources (emitting single photons) of light as it relies on photon counting, and has potential applications in both classical polarization measurements and quantum communication scenarios. In our implementation, we are able to reconstruct the Stokes parameters of pure polarization states with an average fidelity of 99.9%.Publication Narrowband PPKTP source for entangled polarization photons(2011) Joshi, S.K.; Anger, F.; Lamas-Linares, A.; Kurtsiefer, C.; CENTRE FOR QUANTUM TECHNOLOGIES; PHYSICSWe present our efforts to create a narrow-bandwidth source of entangled photons with a high spectral brightness to facilitate their interaction with single trapped atoms. A pump beam with l=405 nm, focused into a type II PPKTP crystal, is down-converted to obtain signal and idler beams; their frequency can be tuned via the temperature of the crystal. By changing the beam waist inside the crystal, we determine the optimal focusing parameters for our source. We observe that weak focusing results in large pair to single ratio (efficiency). © 2011 IEEE.Publication Experimental E91 quantum key distribution(2008) Ling, A.; Peloso, M.; Marcikic, I.; Lamas-Linares, A.; Kurtsiefer, C.; CENTRE FOR QUANTUM TECHNOLOGIES; TEMASEK LABORATORIES; PHYSICSWe report on a field implementation of an E91 protocol. In this experiment, we make use of the violation of a Bell inequality to derive a secure key.Publication Free space quantum cryptography using compact polarization entangled photon pair source(2005) Marcikic, I.; Ling, A.; Looi, S.Y.; Gosal, D.; Lamas-Linares, A.; Kurtsiefer, C.; TEMASEK LABORATORIES; PHYSICSInitial experiments have been performed in order to implement a compact quantum secret key source based on polarization entangled photons (Ekert protocol [1]) which may be suitable for Quantum Distribution Networks or satellite based exchange.Publication Sagnac-loop phase shifter with polarization-independent operation(2011-01) Ng, T.T.; Gosal, D.; Lamas-Linares, A.; Kurtsiefer, C.; CENTRE FOR QUANTUM TECHNOLOGIES; PHYSICSA bulk-optics, polarization-independent phase shifter for photonic quantum information applications is demonstrated. The device is based on a transverse electro-optic modulator in a Sagnac-type loop containing Faraday rotators. This direction-dependent polarization rotation in the loop is combined with a Mach-Zehnder interferometer to form an optical switch with an on/off contrast of 96 and a switching time of 1.6 ns. We demonstrate that the devices operation maintains any arbitrary polarization state. © 2011 American Institute of Physics.Publication Absolute rates of spontaneous parametric down conversion into a single transverse Gaussian mode(2008) Ling, A.; Lamas-Linares, A.; Kurtsiefer, C.; CENTRE FOR QUANTUM TECHNOLOGIES; PHYSICSWe provide expressions for the absolute emission rate of photon pairs produced in SPDC when all interacting fields are in a single transverse Gaussian mode. © 2007 Optical Society of America.Publication Experimental noise-resistant Bell-inequality violations for polarization-entangled photons(2006) Bovino, F.A.; Castagnoli, G.; Cabello, A.; Lamas-Linares, A.; PHYSICSWe experimentally demonstrate that violations of Bell's inequalities for two-photon polarization-entangled states with colored noise are extremely robust, whereas this is not the case for states with white noise. Controlling the amount of noise by using the timing compensation scheme introduced by Kim [Phys. Rev. A 67, 010301(R) (2003)], we have observed violations even for states with very high noise, in excellent agrement with the predictions of Cabello [Phys. Rev. A 72, 052112 (2005)]. © 2006 The American Physical Society.Publication Wigner tomography of two-qubit states and quantum cryptography(2008-10-31) Durt, T.; Kurtsiefer, C.; Lamas-Linares, A.; Ling, A.; CENTRE FOR QUANTUM TECHNOLOGIES; PHYSICSTomography of the two-qubit density matrix shared by Alice and Bob is an essential ingredient for guaranteeing an acceptable margin of confidentiality during the establishment of a secure fresh key through the quantum key distribution scheme. We show how the Singapore protocol for key distribution is optimal from this point of view, due to the fact that it is based on so-called symmetric informationally complete positive-operator-valued measure (SIC POVM) qubit tomography which allows the most accurate full tomographic reconstruction of an unknown density matrix on the basis of a restricted set of experimental data. We illustrate with the help of experimental data the deep connections that exist between SIC POVM tomography and discrete Wigner representations. We also emphasize the special role played by Bell states in this approach and propose a protocol for quantum key distribution during which a third party is able to concede or to deny a posteriori to the authorized users the ability to build a fresh cryptographic key. © 2008 The American Physical Society.Publication Absolute emission rates of spontaneous parametric down-conversion into single transverse Gaussian modes(2008-04-28) Ling, A.; Lamas-Linares, A.; Kurtsiefer, C.; CENTRE FOR QUANTUM TECHNOLOGIES; PHYSICSWe provide an estimate of the absolute values of the emission rate of photon pairs produced by spontaneous parametric down-conversion in a bulk crystal when all interacting fields are in single transverse Gaussian modes. Both collinear and noncollinear configurations are covered, and we arrive at a fully analytical expression for the collinear case. Our results agree reasonably well with values found in typical experiments, which allows this model to be used for understanding the dependency on the relevant experimental parameters. © 2008 The American Physical Society.
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