Realization of single-photon frequency-domain Qubit channels using phase modulators

In a recent paper, [4] have developed a scheme for the stochastic implementation of arbitrary quantum operations on multimode single-photon qudit states by using reconfigurable linear-optic systems. Based on this idea, we explore the use of phase modulation for the realization of qubit channels in the frequency basis. Single-photon states belonging to two different frequency modes differing by the modulator s driving frequency represent the input dual-rail qubit states. The channel is implemented by a phase modulator followed by a fiber Bragg grating, taking advantage of the high degree of reconfigurability and microwave bandwidth shown by electrooptic modulation technology. The channels are realized by a combination of three techniques: 1) suitably designed driving waveforms, which are probabilistically addressed to the modulator; 2) the corresponding addressing probabilities; and 3) the grating transmittance at the values of the frequency basis. The proposed scheme results in nonoptimal success probabilities but is shown to allow for a compact implementation of the conventional qubit random unitary channels and the qubit amplitude-damping channel.This paper was supported in part by the Ministerio de Economia y Competitividad, Spain, through Projects TEC2011-29120-C05-02 and 05 and in part by the Generalitat Valenciana through the PROMETEO 2008/092 research excellency award. Corresponding author: C.R. Fernandez-Pousa (e-mail: [email protected]).Capmany Francoy, J.; Fernández-Pousa, CR. (2012). Realization of single-photon frequency-domain Qubit channels using phase modulators. IEEE Photonics Journal. 4(6):2074-2084. https://doi.org/10.1109/JPHOT.2012.2226022S207420844

Conditional frequency-domain beamsplitters using phase modulators

We propose and explore the families of fully tunable, conditional 2 x 2 frequency-domain beamsplitters that result from sideband coupling in phase modulators. Full tunability is obtained by tailoring the driving voltage feeding the modulators, in a design based on the symmetries of this voltage waveform. The most favorable case in terms of success probability is that of first-sideband coupling, which can be implemented by the use of single-tone phase modulation. The use of this device is illustrated by means of several examples based on the use of a wavelength-routed source of pairs of single-photon frequency-entangled states, showing immediate applications as a means of translating to the frequency-domain quantum-processing protocols based on linear optics.Manuscript received August 31, 2011; revised September 21, 2011; accepted September 22, 2011. Date of publication September 29, 2011; date of current version October 21, 2011. This paper was supported by the Ministerio de Ciencia y Tecnologia, Spain, through Project TEC2008-02606 and through Quantum Optical Information Technology (QOIT): a CONSOLIDER-INGENIO 2010 Project. It is also supported by the Generalitat Valenciana through the PROMETEO 2008/092 research excellency award. Corresponding author: J. Capmany (e-mail: [email protected]).Capmany Francoy, J.; Fernández-Pousa, CR. (2011). Conditional frequency-domain beamsplitters using phase modulators. IEEE Photonics Journal. 3(5):954-967. https://doi.org/10.1109/JPHOT.2011.2170158S9549673

Optimum design for BB84 quantum key distribution in tree-type passive optical networks

We show that there is a tradeoff between the useful key distribution bit rate and the total length of deployed fiber in tree-type passive optical networks for BB84 quantum key distribution applications. A two stage splitting architecture where one splitting is carried in the central office and a second in the outside plant and figure of merit to account for the tradeoff are proposed. We find that there is an optimum solution for the splitting ratios of both stages in the case of Photon Number Splitting (PNS) attacks and Decoy State transmission. We then analyze the effects of the different relevant physical parameters of the PON on the optimum solution.Comment: Published in the Journal of the Optical Society of America

Solitonic Integrable Perturbations of Parafermionic Theories

The quantum integrability of a class of massive perturbations of the parafermionic conformal field theories associated to compact Lie groups is established by showing that they have quantum conserved densities of scale dimension 2 and 3. These theories are integrable for any value of a continuous vector coupling constant, and they generalize the perturbation of the minimal parafermionic models by their first thermal operator. The classical equations-of-motion of these perturbed theories are the non-abelian affine Toda equations which admit (charged) soliton solutions whose semi-classical quantization is expected to permit the identification of the exact S-matrix of the theory.Comment: 18 pages, plain TeX, no figure

Time resolved emission at 1.3 micrometers of a single InAs quantum dot by using a tunable fibre Bragg grating

[EN] Photoluminescence and time resolved photoluminescence from single metamorphic InAs/GaAs quantum dots (QDs) emitting at 1.3 micrometers have been measured by means of a novel fibre-based characterization set-up. We demonstrate that the use of a wavelength tunable fibre Bragg grating filter increases the light collection efficiency by more than one order of magnitude as compared to a conventional grating monochromator. We identified single charged exciton and neutral biexciton transitions in the framework of a random population model. The QD recombination dynamics under pulsed excitation can be understood under the weak quantum confinement potential limit and the interaction between carriers at the wetting layer and QD states.G Munoz-Matutano appreciates valuable help from Professor Miguel Andres (University of Valencia) and thanks the Spanish Juan de la Cierva program (JCI-2011-10686). We acknowledge the support of the FEDER actions UPVOV08-3E-008 and UPVOV10-3E-492, the PROMETEO2009/74 project from Generalitat Valenciana, the Spanish projects TEC2011-29120-C05-01-02-05, the Italian FIRB Project ‘Nanotecnologie e Nanodispositivi per la Societa` dell’Informazione’ and ‘SANDiE’ Network of Excellence of EC, Contract No. NMP4-CT-2004-500101.Muñoz Matutano, G.; Rivas, D.; Ricchiuti, AL.; Barrera Vilar, D.; Fernández Pousa, CR.; Martínez Pastor, J.; Seravalli, L.... (2014). Time resolved emission at 1.3 micrometers of a single InAs quantum dot by using a tunable fibre Bragg grating. Nanotechnology. 25(3):35204-1-35204-7. https://doi.org/10.1088/09574484/25/3/035204S35204-135204-725

Fundamental SNR Limits imposed by ASE in Frequency-Shifting Loops

Recirculating frequency-shifting loops (FSLs) are a simple source of optical frequency combs with bandwidth compatible with microwave technologies. As such, they have demonstrated promising capabilities for telecommunications, remote sensing, and microwave photonics. In these systems, the coherent frequency comb is produced by recirculation of a single frequency laser in a fiber loop containing a frequency shifter. Due to the insertion of an optical amplifier in the loop to compensate for the losses, amplified spontaneous emission (ASE) is inevitably emitted and superimposes to the coherent output. In this paper, we quantify theoretically the contribution of the ASE background to the FSL output for different types of receivers used in FSL-based techniques: direct, self-heterodyne, and dual-comb detection. In particular, we focus on two important practical applications of FSL: coherent optical reflectometry and real-time Fourier transforms of radio-frequency signals. We provide for each of them numerical estimations of the signal-to-noise ratio and dynamic range. This work constitutes a compact framework for the general evaluation of techniques based on FSLs

Impact of Third-Order Intermodulation on the Performance of Subcarrier Multiplexed Quantum Key Distribution

[EN] This paper extends the analysis presented in a previous contribution to account for the effect of third-order intermodulation distortion in the system quantum bit error rate attainable in subcarrier multiplexed quantum key distribution (SCM-QKD) systems, showing that under practical conditions this effect can be safely neglected. When the unconditionally secure key distribution rate is computed for BB84 SCM-QKD systems based on weak coherent pulses and strong reference, it is found a per-channel additional decrease due to nonlinear distortions as low as 1% when compared to the dedicated nonmultiplexed BB84 key distribution channels operated under the same conditions.Manuscript received March 23, 2011; revised June 10, 2011, July 15, 2011; accepted August 12, 2011. Date of publication August 22, 2011; date of current version October 05, 2011. This work was supported in part by the Spanish Government through Quantum Optical Information Technology, a CONSOLIDER-INGENIO 2010 Project, and in part by the Generalitat Valenciana through the PROMETEO 2008/092 Research Excellency Award. The work of C. R. Fernandez-Pousa is supported in part by the Ministerio de Educacion y Ciencia, Spain, through Project TEC2008-02606.Capmany Francoy, J.; Fernández Pousa, CR. (2011). Impact of Third-Order Intermodulation on the Performance of Subcarrier Multiplexed Quantum Key Distribution. Journal of Lightwave Technology. 29(20):3061-3069. https://doi.org/10.1109/JLT.2011.2165526S30613069292

Incoherent Optical Frequency-Domain Reflectometry Based on Homodyne Electro-Optic Downconversion for Fiber-Optic Sensor Interrogation

Fiber-optics sensors using interrogation based on incoherent optical frequency-domain reflectometry (I-OFDR) offer benefits such as the high stability of interference in the radio-frequency (RF) domain and the high SNR due to narrowband RF detection. One of the main impairments of the technique, however, is the necessity of high-frequency detectors and vector network analyzers (VNA) in systems requiring high resolution. In this paper, we report on two C-band implementations of an I-OFDR architecture based on homodyne electro-optic downconversion enabling detection without VNA and using only low-bandwidth, high-sensitivity receivers, therefore alleviating the requirements of conventional I-OFDR approaches. The systems are based on a pair of modulators that are synchronized to perform modulation and homodyne downconversion at a reference frequency of 25.5 kHz. In the first system, we attain centimeter resolution with a sensitivity down to −90 dB using the modulation frequency range comprised between 3.2 and 14.2 GHz. In the second, we measured, for the first time using this approach, Rayleigh backscattering traces in standard single mode fiber with resolution of 6 m and a sensitivity of −83 dB by use of the 10.1−30.1 MHz range. These results show the feasibility of these simple, homodyne downconversion I-OFDR systems as compact interrogators for distributed or quasi-distributed optical fiber sensors