Marcikic,Ivan
Email Address
phymi@nus.edu.sg
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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 Joint spectrum mapping of polarization entanglement in spontaneous parametric down-conversion(2007-04-26) Poh, H.S.; Lum, C.Y.; Marcikic, I.; Lamas-Linares, A.; Kurtsiefer, C.; TEMASEK LABORATORIES; PHYSICSPolarization-entangled photon pairs can be efficiently prepared into pure Bell states with a high fidelity via type-II spontaneous parametric down-conversion (SPDC) of narrow-band pump light. However, the use of femtosecond pump pulses to generate multiphoton states with precise timing often requires spectral filtering to maintain a high quality of polarization entanglement. This typically reduces the efficiency of photon pair collection. We experimentally map the polarization correlations of photon pairs from such a source over a range of down-converted wavelengths with a high spectral resolution and find strong polarization correlations everywhere. A spectrally dependent imbalance between contributions from the two possible decay paths of SPDC is identified as the reason for a reduction in entanglement quality observed with femtosecond pump pulses. Our spectral measurements allow us to predict the polarization correlations for arbitrary filter profiles when the frequency degree of freedom of the photon pairs is ignored. © 2007 The American Physical Society.Publication Free-space quantum key distribution with entangled photons(2006) Marcikic, I.; Lamas-Linares, A.; Kurtsiefer, C.; TEMASEK LABORATORIES; PHYSICSThe authors report on a complete experimental implementation of a quantum key distribution protocol through a free-space link using polarization-entangled photon pairs from a compact parametric downconversion source. Over 10 h of uninterrupted communication between sites 1.5 km apart, they observe average key generation rates of 630/s after error correction and privacy amplification. Their scheme requires no specific hardware channel for synchronization apart from a classical wireless link, and no explicit random number generator. © 2006 American Institute of Physics.Publication Eliminating spectral distinguishability in ultrafast spontaneous parametric down-conversion(2009-10-14) Poh, H.S.; Lim, J.; Marcikic, I.; Lamas-Linares, A.; Kurtsiefer, C.; CENTRE FOR QUANTUM TECHNOLOGIES; TEMASEK LABORATORIES; PHYSICSGeneration of polarization-entangled photon pairs with a precise timing through down-conversion of femtosecond pulses is often faced with a degraded polarization entanglement quality. In a previous experiment, we have shown that this degradation is induced by spectral distinguishability between the two decay paths, in accordance with theoretical predictions. Here, we present an experimental study of the spectral compensation scheme proposed and first implemented by Kim and Grice [J. Mod. Opt. 49, 2309 (2002)]. By measuring the joint spectral properties of the polarization correlations of the photon pairs, we show that the spectral distinguishability between the down-converted components is eliminated. This scheme results in a polarization visibility of 97.9±0.5% without any spectral filtering. © 2009 The American Physical Society.Publication Experimental quantum key distribution based on a Bell test(2008-08-20) Ling, A.; Peloso, M.P.; Marcikic, I.; Scarani, V.; Lamas-Linares, A.; Kurtsiefer, C.; CENTRE FOR QUANTUM TECHNOLOGIES; TEMASEK LABORATORIES; PHYSICSWe report on a complete free-space field implementation of a modified Ekert protocol for quantum key distribution using entangled photon pairs. For each photon pair we perform a random choice between key generation and a Bell inequality. The amount of violation is used to determine the possible knowledge of an eavesdropper to ensure security of the distributed final key. © 2008 The American Physical Society.