THE ORBITAL ANGULAR MOMENTUM (OAM) SPATIAL DEGREE OF FREEDOM OF LIGHT HAS BEEN WIDELY EXPLORED IN MANY APPLICATIONS, INCLUDING TELECOMMUNICATIONS, QUANTUM INFORMATION, AND LIGHT-BASED MICROMANIPULATION. THE ABILITY TO SEPARATE AND DISTINGUISH BETWEEN THE DIFFERENT TRANSVERSE SPATIAL MODES IS CALLED MODE SORTING OR MODE DEMULTIPLEXING, AND IT IS ESSENTIAL TO RECOVER THE ENCODED INFORMATION IN SUCH APPLICATIONS. AN IDEAL D MODE SORTER SHOULD BE ABLE TO FAITHFULLY DISTINGUISH BETWEEN THE DIFFERENT D SPATIAL MODES, WITH MINIMAL LOSSES, AND HAVE D OUTPUTS AND FAST RESPONSE TIMES. ALL PREVIOUS MODE SORTERS RELY ON BULK OPTICAL ELEMENTS, SUCH AS SPATIAL LIGHT MODULATORS, WHICH CANNOT BE QUICKLY TUNED AND HAVE ADDITIONAL LOSSES IF THEY ARE TO BE INTEGRATED WITH OPTICAL FIBER SYSTEMS. HERE, WE PROPOSE AND EXPERIMENTALLY DEMONSTRATE, TO THE BEST OF OUR KNOWLEDGE, THE FIRST ALL-IN-FIBER METHOD FOR OAM MODE SORTING WITH ULTRAFAST DYNAMIC RECONFIGURABILITY. OUR SCHEME FIRST DECOMPOSES THE OAM MODE IN-FIBER-OPTICAL LINEARLY POLARIZED (LP) MODES AND THEN INTERFEROMETRICALLY RECOMBINES THEM TO DETERMINE THE TOPOLOGICAL CHARGE, THUS CORRECTLY SORTING THE OAM MODE. IN ADDITION, OUR SETUP CAN ALSO BE USED TO PERFORM ULTRAFAST ROUTING OF THE OAM MODES. THESE RESULTS SHOW A NOVEL AND FIBER-INTEGRATED FORM OF OPTICAL SPATIAL MODE SORTING THAT CAN BE READILY USED FOR MANY NEW APPLICATIONS IN CLASSICAL AND QUANTUM INFORMATION PROCESSING.

WE INVESTIGATE THEORETICALLY AND EXPERIMENTALLY THE OPTICAL SECOND HARMONIC GENERATION (SHG) WITH A TWISTED GAUSSIAN SCHELL MODEL (TGSM) BEAM AS THE FUNDAMENTAL FIELD. WE USE TYPE-II PHASE MATCHING AND ANALYZE THE CROSS SPECTRAL DENSITY (CSD) OF THE SHG OUTPUT BEAM WHEN THE INPUT FUNDAMENTAL IS PREPARED WITH A TGSM STRUCTURE. WE ANALYZE TWO SYNTHETIZATION METHODS FOR PREPARING THE TGSM FUNDAMENTAL BEAM AND WE FIND THAT FOR ONE METHOD THE SHG IS ALSO A TGSM BEAM. FOR THE OTHER METHOD, WE FIND THAT THE SHG IS NOT A TGSM BEAM AND PRESENTS AN ANOMALOUS CSD POSSESSING A DIP INSTEAD OF A PEAK IN THE TRANSVERSE SPATIAL STRUCTURE. MOREOVER, WE SHOW THAT THE DIP DEPTH IS DIRECTLY RELATED TO THE TWISTED PHASE PARAMETER, BEING ABSENT FOR A NON TWISTED GSM BEAM. OUR RESULTS SHOW THAT THE SHG FROM A FUNDAMENTAL TGSM BEAM CAN RESULT IN A DOUBLED FREQUENCY TGSM OR IN A NON-TGSM BEAM DEPENDING ON THE SYNTHETIZATION METHOD.

WE REPORT ON A NEW CLASS OF DIMENSION WITNESSES, BASED ON QUANTUM RANDOM ACCESS CODES, WHICH ARE A FUNCTION OF THE RECORDED STATISTICS AND THAT HAVE DIFFERENT BOUNDS FOR ALL POSSIBLE DECOMPOSITIONS OF A HIGH-DIMENSIONAL PHYSICAL SYSTEM. THUS, IT CERTIFIES THE DIMENSION OF THE SYSTEM AND HAS THE NEW DISTINCT FEATURE OF IDENTIFYING WHETHER THE HIGH-DIMENSIONAL SYSTEM IS DECOMPOSABLE IN TERMS OF LOWER DIMENSIONAL SUBSYSTEMS. TO DEMONSTRATE THE PRACTICABILITY OF THIS TECHNIQUE, WE USED IT TO EXPERIMENTALLY CERTIFY THE GENERATION OF AN IRREDUCIBLE 1024-DIMENSIONAL PHOTONIC QUANTUM STATE. THEREFORE, CERTIFYING THAT THE STATE IS NOT MULTIPARTITE OR ENCODED USING NONCOUPLED DIFFERENT DEGREES OF FREEDOM OF A SINGLE PHOTON. OUR PROTOCOL SHOULD FIND APPLICATIONS IN A BROAD CLASS OF MODERN QUANTUM INFORMATION EXPERIMENTS ADDRESSING THE GENERATION OF HIGH-DIMENSIONAL QUANTUM SYSTEMS, WHERE QUANTUM TOMOGRAPHY MAY BECOME INTRACTABLE.

THE USE OF QUALITATIVE ALGORITHMS IN IMAGES WITH DYNAMIC SPECKLE ALLOWS GENERATING A THREE-DIMENSIONAL INTENSITY MAP, WHICH CORRELATES WITH THE SAMPLE ACTIVITY. SAMPLES IN AN EVAPORATION STATE WILL PRESENT TEMPORARY MOBILITY RELATED TO THEIR VOLUME, WHICH ALLOWS CHARACTERIZING THEIR TOPOGRAPHY. HOWEVER, THE QUALITY OF THE TOPOGRAPHIC CHARACTERIZATION DEPENDS ON THE ILLUMINATION PROFILE AND THE NUMBER OF IMAGES OR FRAMES USED. IN THIS PAPER, A REVIEW OF VARIOUS QUALITATIVE PROCESSING ALGORITHMS IS CARRIED OUT IN ORDER TO EVALUATE THEIR ROBUSTNESS TO THE NUMBER OF FRAMES AND THEIR DEPENDENCE ON THE BEAM PROFILE, EVALUATING THE CHARACTERIZATION OF TOPOGRAPHY HIDDEN BY A LAYER OF PAINT IN PROCESS OF DRYING. WE USE AN ALUMINUM STRUCTURE WITH PERFORATIONS OF DIFFERENT DIAMETERS AND DEPTHS AS A SAMPLE. AMONG THE ALGORITHMS USED, WE HIGHLIGHT THE RESULTS OBTAINED BY THE NORMALIZED DJC METHOD, WHICH CHARACTERIZES THE TOPOGRAPHY OF OUR SAMPLE WITH A CORRELATION OF 0.98 AND PRESENTS STABILITY TO THE NUMBER OF FRAMES USED. THUS, WITH THESE RESULTS WE VALIDATE THE USE OF DYNAMIC SPECKLE IN THE CHARACTERIZATION OF A SURFACE COVERED WITH PAINT.

THE CAPACITY OF OPTICAL COMMUNICATION CHANNELS CAN BE INCREASED BY SPACE DIVISION MULTIPLEXING IN STRUCTURED OPTICAL FIBERS. RADIAL CORE OPTICAL FIBERS ALLOWS FOR THE PROPAGATION OF TWISTED LIGHT?EIGENMODES OF ORBITAL ANGULAR MOMENTUM, WHICH HAVE ATTRACTED CONSIDERABLE ATTENTION FOR HIGH-DIMENSIONAL QUANTUM INFORMATION. HERE WE STUDY THE GENERATION OF ENTANGLED PHOTONS THAT ARE TAILOR-MADE FOR COUPLING INTO RING CORE OPTICAL FIBERS. WE SHOW THAT THE COUPLING OF PHOTON PAIRS PRODUCED BY PARAMETRIC DOWN-CONVERSION CAN BE INCREASED BY CLOSE TO A FACTOR OF THREE BY PUMPING THE NON-LINEAR CRYSTAL WITH A PERFECT VORTEX MODE WITH ORBITAL ANGULAR MOMENTUM ?, RATHER THAN A GAUSSIAN MODE. MOREOVER, THE TWO-PHOTON ORBITAL ANGULAR MOMENTUM SPECTRUM HAS A NEARLY CONSTANT SHAPE. THIS PROVIDES AN INTERESTING SCENARIO FOR QUANTUM STATE ENGINEERING, AS PUMPING THE CRYSTAL WITH A SUPERPOSITION OF PERFECT VORTEX MODES CAN BE USED IN CONJUNCTION WITH THE MODE FILTERING PROPERTIES OF THE RING CORE FIBER TO PRODUCE SIMPLE AND INTERESTING QUANTUM STATES.

WE INTRODUCE A METHOD TO ESTIMATE UNKNOWN PURE D-DIMENSIONAL QUANTUM STATES USING THE PROBABILITY DISTRIBUTIONS ASSOCIATED WITH ONLY THREE MEASUREMENT BASES. THE MEASUREMENT RESULTS OF 2D PROJECTORS ARE USED TO GENERATE A SET OF 2 D-1 STATES, THE VALUE OF THE LIKELIHOOD FUNCTION OF WHICH IS EVALUATED USING THE MEASUREMENT RESULTS OF THE REMAINING D PROJECTORS. THE STATE WITH THE HIGHEST VALUE OF THE LIKELIHOOD FUNCTION IS THE ESTIMATE OF THE UNKNOWN STATE. THE METHOD ESTIMATES ALL PURE STATES EXCEPT FOR A NULL-MEASURE SET, WHICH CAN BE OVERCOME BY ADAPTING TWO BASES. THE VIABILITY OF THE PROTOCOL IS EXPERIMENTALLY DEMONSTRATED USING TWO DIFFERENT AND COMPLEMENTARY HIGH-DIMENSIONAL QUANTUM INFORMATION PLATFORMS. FIRST, BY EXPLORING THE PHOTONIC PATH-ENCODING STRATEGY, WE VALIDATE THE METHOD ON A SINGLE EIGHT-DIMENSIONAL QUANTUM SYSTEM. THEN, WE RESORT TO THE FIVE-SUPERCONDUCTING-QUBIT IBM QUANTUM PROCESSOR TO DEMONSTRATE THE HIGH PERFORMANCE OF THE METHOD IN THE MULTIPARTITE SCENARIO.

IN OPTICAL COMMUNICATIONS, SPACE-DIVISION MULTIPLEXING IS A PROMISING STRATEGY TO AUGMENT THE FIBER NETWORK CAPACITY. IT RELIES ON MODERN FIBER DESIGNS THAT SUPPORT THE PROPAGATION OF MULTIPLE SPATIAL MODES. ONE OF THESE FIBERS, THE RING-CORE FIBER (RCF), IS ABLE TO PROPAGATE MODES THAT CARRY ORBITAL ANGULAR MOMENTUM (OAM), AND HAS BEEN SHOWN TO ENHANCE NOT ONLY CLASSICAL BUT ALSO QUANTUM COMMUNICATION SYSTEMS. TYPICALLY, THE RCF SPATIAL MODES ARE USED AS ORTHOGONAL TRANSMISSION CHANNELS FOR DATA STREAMS THAT ARE COUPLED INTO THE FIBER USING DIFFERENT FREE SPACE BEAMS. FREE SPACE BEAMS COMMONLY USED ARE LAGUERRE-GAUSSIAN (LG) AND PERFECT VORTEX (PV) BEAMS. HERE, WE STUDY THE OPTIMAL CONDITIONS TO MULTIPLEX INFORMATION INTO RING-CORE FIBERS IN THIS SCHEME. WE STUDY THE BEAM COUPLING EFFICIENCY USING THE OVERLAP BETWEEN FREE SPACE BEAMS AND RCF BOUND BEAMS AND DETERMINE WHICH ARE THE MOST RELEVANT LG BEAMS TO BE CONSIDERED AND HOW THEIR COUPLING EFFICIENCY CAN BE MAXIMIZED BY PROPERLY ADJUSTING THE BEAM WIDTH WITH RESPECT TO THE FIBER PARAMETERS. OUR RESULTS SHOW THAT THE COUPLING EFFICIENCY DEPENDS UPON THE OAM VALUE AND THAT THIS CAN LIMIT THE ACHIEVABLE TRANSMISSION RATES IN SDM SYSTEMS. IN THIS REGARD, WE FIND OPTIMAL COUPLING CONFIGURATIONS FOR LG BEAMS BASED ON THE RCF FIBER AND BEAM PARAMETERS. FURTHER, WE STUDY THE PV BEAM THAT ALLOWS FOR NEARLY PERFECT COUPLING EFFICIENCIES FOR ALL SPATIAL MODES SUPPORTED BY THESE FIBERS. PV BEAMS PRESENT HIGHER COUPLING EFFICIENCIES THAN LG BEAMS AND NEGLIGIBLE DEPENDENCE ON THE OAM VALUE, THUS OFFERING AN ATTRACTIVE SOLUTION TO MULTIPLEX HIGH COUNTS OF OAM CHANNELS FROM FREE SPACE INTO A RING-CORE FIBER USING A SINGLE COUPLING CONFIGURATION.

THE TWISTED GAUSSIAN SCHELL MODEL DESCRIBES A FAMILY OF PARTIALLY COHERENT BEAMS THAT PRESENT SEVERAL INTERESTING CHARACTERISTICS, AND AS SUCH HAVE ATTRACTED ATTENTION IN CLASSICAL AND QUANTUM OPTICS. RECENT TECHNIQUES HAVE BEEN DEMONSTRATED TO SYNTHESIZE THESE BEAMS FROM A COHERENT SOURCE USING A DISCRETE SET OF """"""""""""""""""""""""""""""""PSEUDO-MODES"""""""""""""""""""""""""""""""", WHERE THE PHASE OF EACH MODE IS RANDOMIZED SO THAT THEY ARE MUTUALLY INCOHERENT. HERE WE INVESTIGATE THIS TECHNIQUE AND EVALUATE THE RESULTING BEAM PARAMETERS, SUCH AS DIVERGENCE, COHERENCE LENGTH AND TWIST PHASE. WE SHOW THAT FOR A FINITE SET OF MODES THERE IS ALSO SOME RESIDUAL COHERENCE, WHICH CAN HAVE AN OBSERVABLE EFFECT. A THEORETICAL MODEL IS DEVELOPED FOR THE OUTPUT FIELD THAT INCLUDES RESIDUAL COHERENCE AND AGREES VERY WELL WITH EXPERIMENTAL DATA. IN ADDITION, WE DEMONSTRATE A SIMPLE METHOD TO MEASURE THE TWIST PHASE USING DOUBLE SLIT INTERFERENCE.

HIGH-DIMENSIONAL QUANTUM INFORMATION PROCESSING HAS BECOME A MATURE FIELD OF RESEARCH WITH SEVERAL DIFFERENT APPROACHES BEING ADOPTED FOR THE ENCODING OF D-DIMENSIONAL QUANTUM SYSTEMS. SUCH PROGRESS HAS FUELED THE SEARCH OF RELIABLE QUANTUM TOMOGRAPHIC METHODS AIMING FOR THE CHARACTERIZATION OF THESE SYSTEMS, MOST OF THESE METHODS BEING SPECIFICALLY DESIGNED FOR A GIVEN SCENARIO. HERE, WE REPORT ON A TOMOGRAPHIC METHOD BASED ON MULTIPLY SYMMETRIC STATES AND ON EXPERIMENTAL INVESTIGATIONS TO STUDY ITS PERFORMANCE IN HIGHER DIMENSIONS. UNLIKE OTHER METHODS, IT IS GUARANTEED TO EXIST IN ANY DIMENSION AND PROVIDES A SIGNIFICANT REDUCTION IN THE NUMBER OF MEASUREMENT OUTCOMES WHEN COMPARED TO STANDARD QUANTUM TOMOGRAPHY. FURTHERMORE, IN THE CASE OF ODD DIMENSIONS, THE METHOD REQUIRES THE LEAST POSSIBLE NUMBER OF MEASUREMENT OUTCOMES. IN OUR EXPERIMENT WE ADOPT THE TECHNIQUE WHERE HIGH-DIMENSIONAL QUANTUM STATES ARE ENCODED USING THE LINEAR TRANSVERSE MOMENTUM OF SINGLE PHOTONS AND ARE CONTROLLED BY SPATIAL LIGHT MODULATORS. OUR RESULTS SHOW THAT FIDELITIES OF 0.984±0.009 WITH ENSEMBLE SIZES OF ONLY 1.5×105 PHOTONS IN DIMENSION D=15 CAN BE OBTAINED IN TYPICAL LABORATORY CONDITIONS, THUS SHOWING ITS PRACTICABILITY IN HIGHER DIMENSIONS.

QUANTUM RESOURCES CAN IMPROVE COMMUNICATION COMPLEXITY PROBLEMS (CCPS) BEYOND THEIR CLASSICAL CONSTRAINTS. ONE QUANTUM APPROACH IS TO SHARE ENTANGLEMENT AND CREATE CORRELATIONS VIOLATING A BELL INEQUALITY, WHICH CAN THEN ASSIST CLASSICAL COMMUNICATION. A SECOND APPROACH IS TO RESORT SOLELY TO THE PREPARATION, TRANSMISSION, AND MEASUREMENT OF A SINGLE QUANTUM SYSTEM, IN OTHER WORDS, QUANTUM COMMUNICATION. HERE, WE SHOW THE ADVANTAGES OF THE LATTER OVER THE FORMER IN HIGH-DIMENSIONAL HILBERT SPACE. WE FOCUS ON A FAMILY OF CCPS, BASED ON FACET BELL INEQUALITIES, STUDY THE ADVANTAGE OF HIGH-DIMENSIONAL QUANTUM COMMUNICATION, AND REALIZE SUCH QUANTUM COMMUNICATION STRATEGIES USING UP TO TEN-DIMENSIONAL SYSTEMS. THE EXPERIMENT DEMONSTRATES, FOR GROWING DIMENSION, AN INCREASING ADVANTAGE OVER QUANTUM STRATEGIES BASED ON BELL INEQUALITY VIOLATION. FOR SUFFICIENTLY HIGH DIMENSIONS, QUANTUM COMMUNICATION ALSO SURPASSES THE LIMITATIONS OF THE POSTQUANTUM BELL CORRELATIONS OBEYING ONLY LOCALITY IN THE MACROSCOPIC LIMIT. WE FIND THAT THE ADVANTAGES ARE TIED TO THE USE OF MEASUREMENTS THAT ARE NOT RANK-ONE PROJECTIVE, AND PROVIDE AN EXPERIMENTAL SEMI-DEVICE-INDEPENDENT FALSIFICATION OF SUCH MEASUREMENTS IN HILBERT SPACE DIMENSION SIX.

MULTI-PORT BEAM SPLITTERS ARE CORNERSTONE DEVICES FOR HIGH-DIMENSIONAL QUANTUM INFORMATION TASKS, WHICH CAN OUTPERFORM THE TWO-DIMENSIONAL ONES. NONETHELESS, THE FABRICATION OF SUCH DEVICES HAS PROVEN TO BE CHALLENGING WITH PROGRESS ONLY RECENTLY ACHIEVED WITH THE ADVENT OF INTEGRATED PHOTONICS. HERE, WE REPORT ON THE PRODUCTION OF HIGH-QUALITY N×N (WITH N=4,7) MULTI-PORT BEAM SPLITTERS BASED ON A NEW SCHEME FOR MANIPULATING MULTI-CORE OPTICAL FIBERS. BY EXPLORING THEIR COMPATIBILITY WITH OPTICAL FIBER COMPONENTS, WE CREATE FOUR-DIMENSIONAL QUANTUM SYSTEMS AND IMPLEMENT THE MEASUREMENT-DEVICE-INDEPENDENT RANDOM NUMBER GENERATION TASK WITH A PROGRAMMABLE FOUR-ARM INTERFEROMETER OPERATING AT A 2 MHZ REPETITION RATE. DUE TO THE HIGH VISIBILITIES OBSERVED, WE SURPASS THE ONE-BIT LIMIT OF BINARY PROTOCOLS AND ATTAIN 1.23 BITS OF CERTIFIED PRIVATE RANDOMNESS PER EXPERIMENTAL ROUND. OUR RESULT DEMONSTRATES THAT FAST SWITCHING, LOW LOSS, AND HIGH OPTICAL QUALITY FOR HIGH-DIMENSIONAL QUANTUM INFORMATION CAN BE SIMULTANEOUSLY ACHIEVED WITH MULTI-CORE FIBER TECHNOLOGY.

STIMULATED PARAMETRIC DOWN-CONVERSION IS A NONLINEAR OPTICAL PROCESS THAT CAN BE USED FOR PHASE CONJUGATION AND FREQUENCY CONVERSION OF AN OPTICAL FIELD. A PRECISE DESCRIPTION OF THE OUTGOING STIMULATED FIELD HAS BEEN DEVELOPED FOR THE CASE WHERE THE INPUT PUMP AND SEED FIELDS ARE COHERENT. HOWEVER, PARTIALLY COHERENT BEAMS CAN HAVE INTERESTING AND IMPORTANT CHARACTERISTICS THAT ARE ABSENT IN COHERENT BEAMS. ONE EXAMPLE IS THE TWIST PHASE, A NOVEL OPTICAL PHASE THAT CAN APPEAR IN PARTIALLY COHERENT GAUSSIAN BEAMS AND GIVES RISE TO A NONZERO ORBITAL ANGULAR MOMENTUM. HERE, WE CONSIDER STIMULATED DOWN-CONVERSION FOR PARTIALLY COHERENT INPUT FIELDS. AS A CASE STUDY, WE USE TWISTED GAUSSIAN SCHELL-MODEL BEAMS AS THE SEED AND PUMP BEAMS IN STIMULATED PARAMETRIC DOWN-CONVERSION. IT IS SHOWN BOTH THEORETICALLY AND EXPERIMENTALLY THAT THE STIMULATED IDLER BEAM CAN BE WRITTEN AS A TWISTED GAUSSIAN SCHELL-MODEL BEAM, WHERE THE BEAM PARAMETERS ARE DETERMINED ENTIRELY BY THE SEED AND PUMP. WHEN THE PUMP BEAM IS COHERENT, THE TWIST PHASE OF THE IDLER IS THE CONJUGATE OF THAT OF THE SEED. THESE RESULTS COULD BE USEFUL FOR THE CORRECTION OF WAVEFRONT DISTORTION SUCH AS IN ATMOSPHERIC TURBULENCE IN OPTICAL COMMUNICATION CHANNELS, AND SYNTHESIS OF PARTIALLY COHERENT BEAMS.

DEVICE AND SEMI-DEVICE-INDEPENDENT PRIVATE QUANTUM RANDOMNESS GENERATORS ARE CRUCIAL FOR APPLICATIONS REQUIRING PRIVATE RANDOMNESS. HOWEVER, THEY ARE VULNERABLE TO DETECTION INEFFICIENCY ATTACKS AND THIS LIMITS SEVERELY THEIR USAGE FOR PRACTICAL PURPOSES. HERE, WE PRESENT A METHOD FOR PROTECTING SEMI-DEVICE-INDEPENDENT PRIVATE QUANTUM RANDOMNESS GENERATORS IN PREPARE-AND-MEASURE SCENARIOS AGAINST DETECTION INEFFICIENCY ATTACKS. THE KEY IDEA IS THE INTRODUCTION OF A BLOCKING DEVICE THAT ADDS FAILURES IN THE COMMUNICATION BETWEEN THE PREPARATION AND MEASUREMENT DEVICES. WE PROVE THAT, FOR ANY DETECTION EFFICIENCY, THERE IS A BLOCKING RATE THAT PROVIDES PROTECTION AGAINST THESE ATTACKS. WE EXPERIMENTALLY DEMONSTRATE THE GENERATION OF PRIVATE RANDOMNESS USING WEAK COHERENT STATES AND STANDARD AVALANCHE PHOTO-DETECTORS.

WE PERFORM A ROBUST SELF-TESTING CERTIFICATION OF TWO FOUR-DIMENSIONAL MUTUALLY UNBIASED BASES IN A HIGH-QUALITY OPTICAL CONFIGURATION BUILT WITH COMMERCIAL MULTICORE FIBER. WE ALSO EVALUATE THE RANDOMNESS PRODUCED. OUR RESULTS REPRESENT AN IMPORTANT STEP TOWARDS PRACTICAL SELF-TESTING IN HIGH-DIMENSIONAL QUANTUM INFORMATION TECHNOLOGIES.

IN THE DEVICE-INDEPENDENT QUANTUM-INFORMATION APPROACH, THE IMPLEMENTATION OF A GIVEN TASK CAN BE SELF-TESTED SOLELY FROM THE RECORDED STATISTICS AND WITHOUT DETAILED MODELS FOR THE EMPLOYED DEVICES. EVEN THOUGH EXPERIMENTALLY DEMANDING, IT PROVIDES APPEALING VERIFICATION SCHEMES FOR ADVANCED QUANTUM TECHNOLOGIES THAT NATURALLY FULFIL THE ASSOCIATED REQUIREMENTS. IN THIS WORK, WE EXPERIMENTALLY STUDY WHETHER SELF-TESTING PROTOCOLS CAN BE ADOPTED TO CERTIFY THE PROPER FUNCTIONING OF QUANTUM DEVICES BUILT WITH MODERN SPACE-DIVISION MULTIPLEXING OPTICAL FIBER TECHNOLOGY. SPECIFICALLY, WE CONSIDER THE PREPARE-AND-MEASURE PROTOCOL OF FARKAS AND KANIEWSKI [PHYS. REV. A 99, 032316 (2019)] FOR SELF-TESTING MEASUREMENTS CORRESPONDING TO MUTUALLY UNBIASED BASES (MUBS) IN A DIMENSION D > 2 . IN OUR SCHEME, THE STATE PREPARATION AND MEASUREMENT STAGES ARE IMPLEMENTED USING A MULTIARM INTERFEROMETER BUILT WITH MULTICORE OPTICAL FIBERS AND RELATED COMPONENTS. DUE TO THE HIGH OVERLAP OF THE INTERFEROMETER?S OPTICAL MODES ACHIEVED WITH THIS TECHNOLOGY, WE ARE ABLE TO REACH THE REQUIRED VISIBILITIES FOR SELF-TESTING THE IMPLEMENTATION OF TWO FOUR-DIMENSIONAL MUBS. WE ALSO QUANTIFY TWO OPERATIONAL QUANTITIES OF THE MEASUREMENTS: (I) THE INCOMPATIBILITY ROBUSTNESS, CONNECTED TO BELL VIOLATIONS, AND (II) THE RANDOMNESS EXTRACTABLE FROM THE OUTCOMES. SINCE MUBS LIE AT THE CORE OF SEVERAL QUANTUM-INFORMATION PROTOCOLS, OUR RESULTS ARE OF PRACTICAL INTEREST FOR FUTURE QUANTUM WORKS RELYING ON SPACE-DIVISION MULTIPLEXING OPTICAL FIBERS.

ORBITAL ANGULAR MOMENTUM CAN BE USED TO IMPLEMENT HIGH CAPACITY DATA TRANSMISSION SYSTEMS THAT CAN BE APPLIED FOR CLASSICAL AND QUANTUM COMMUNICATIONS. HERE WE EXPERIMENTALLY STUDY THE GENERATION AND TRANSMISSION PROPERTIES OF THE SO-CALLED PERFECT VORTEX BEAMS AND THE LAGUERRE-GAUSSIAN BEAMS IN RING-CORE OPTICAL FIBERS. OUR RESULTS SHOW THAT WHEN USING A SINGLE PREPARATION STAGE, THE PERFECT VORTEX BEAMS PRESENT LESS RING-RADIUS VARIATION THAT ALLOWS COUPLING OF HIGHER OPTICAL POWER INTO A RING CORE FIBER. THESE RESULTS LEAD TO LOWER POWER REQUIREMENTS TO ESTABLISH FIBER-BASED COMMUNICATIONS LINKS USING ORBITAL ANGULAR MOMENTUM AND SET THE STAGE FOR FUTURE IMPLEMENTATIONS OF HIGH-DIMENSIONAL QUANTUM COMMUNICATION OVER SPACE DIVISION MULTIPLEXING FIBERS.