Francisco Mendieta

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In this work we present the principles and experimental demonstration of a BB84 Quantum Key Distribution (QKD) one way system using fainted pulses and a Quadrature Phase-Shift-Keying (QPSK) format including a timemultiplexed unmodulated carrier reference at Alice’s end, and a differential homodyne reception at Bob’s end. We also describe the secure(More)
In this paper, we present the prototype of an ATPsystem intended to be used in an optical quantum communications link between a Cubesat and an optical earth station. The ATP system is designed in such way that alignment on the satellite with respect to the optical earth station will be carried out based on the concept of an artificial star with the help of(More)
In this work we first present the SATEX 1 microsatellite project, as our initial experience in space optical communications; we then describe the current activities on the design and development of the SENSAT 1 nanosatellite and especially its optical communications payload, consisting of an 830 nm downlink optical transmitter for data communications, with(More)
The Optical Wireless Communications (OWC) is a type of communications system that uses the atmosphere as a communications channel. The OWC systems are attractive to provide broadband services due to their inherent wide bandwidth, easy deployment and no license requirement. The idea to employ the atmosphere as transmission media arises from the invention of(More)
We present an eight-port homodyne receiver implemented in free space technology for detection of weak coherent states that carry binary information. For transmitted power economy, we use suppressedcarrier modulation, therefore, we have implemented an optical Costasloop-type carrier synchronizer. We obtain the quasiprobability Q function from the in-phase(More)
In this work we present the principles of a flexible quantum key distribution (QKD) system using quadrature-phase-shift-keying (QPSK) base and symbol encoding and dual-threshold balanced homodyne detection (BHD) scheme. We give its security proofs and we compare its performance experimentally with a photon counting detection scheme.
A free-space experimental set-up for measuring the quadrature components of weak-coherent-state laser signals, based on a homodyne Costas loop configuration is presented. Loop parameters are optimized as a trade-off between quantum and phase noises. Using BPSK modulation, measurements on the mutual information are presented for different photon numbers and(More)
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