Quantum entanglement of photons and Bell theorem test at CEMS

Photonics and Quantum Optics Research Unit of Center of Excellence for Advanced Materials and Sensors at the Ruđer Bošković Institute announces realization and measurement of quantum entanglement of photon pairs. The experimental setup is schematically shown in the figure. A 405 nm wavelength purple laser beam is fed into Sagnac interferometer containing a periodically-poled crystal of potassium titanil-phosphate (PPKTP), schematically shown below on the left. The actual setup is shown on the right. Thanks to the nonlinear optical nature of the crystal and the specifically selected orientation of its lattice axes, some of the purple photons undergo a process of spontaneous parametric downconversion and thus split into a pair of infrared photons that are quantum entangled in polarization. Quantum entanglement of photons was evaluated in two ways.

 

First, we measured correlation of polarization of paired photons. To that end, each photon is sent to one of the polarization-measuring stations, named Alice and Bob. The actual setup is shown below. Alice and Bob are each realized as a polarizer mounted on computer-controlled, motorized mount, followed by an optical-fiber-coupled photon detector, as shown in the photo of the actual setup.

Alice can measure polarization along one of 4 special orientations (horizontal (H), vertical (V), diagonal (D) and anti-diagonal (A)). For each of the Alice’s orientations, Bob rotates his polarization analyzer for a full circle and they evaluate probability of measuring a photon polarization along their respective orientation, as a function of Bob’s analyzer angle. The probability forms a sinusoidal fringe, as shown in the figure below. Visibility greater than 50% for all 4 fringes is not possible if photons in a pair have predetermined polarizations. On the other hand, if photons are entangled, then visibility of all 4 fringes can reach the theoretical maximum of 100%. With our source we have obtained: V= (99,8 +/- 0,6) %, V= (99,7 +/- 0,4) %, V= (98,5 +/- 0,4) %, V= (98,3 +/- 0,4) %, as shown in the figure, which indicates near-maximal entanglement of photons.

We also used the Bell’s theorem and performed measurement of Clauser, Horne, Shimony, Holt (CHSH) parameter S, to test the CHSH form of Bell’s inequality. Classical physics predicts S ≤ 2, while quantum physics allows 2 < S ≤ 2√2  2.828. We have experimentally obtained the value of S = 2,803 +/- 0,007 which is more than 114 standard deviations greater than the maximum value of 2 allowed by classical physics, again indicating the near-maximal entanglement.

These results demonstrate the non-local behaviour of quantum-entangled photon pairs, which is that the measurement of polarization performed on one photon has an immediate impact on the result of measurement of polarization on the other photon.

Ostvareno generiranje parova polarizacijski spregnutih fotona

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Sa zadovoljstvom objavljujemo da je 9. travnja 2018. istraživači Istraživačke jedinice Fotonika i kvantna optika Znanstvenog centra izvrsnosti za napredne materijale i senzore, na Institutu Ruđer Bošković, dovršili su gradnju eksperimentalnog postava izvora parova spregnutih fotona zasnovanog na procesu spontane parametarske pretvorbe (Engl. spontaneous parametric downconversion (SPDC), kolinearni proces tipa II) fotona valne duljine 405 nm u parove infracrvenih fotona u PPKTP kristalu te optičkom postavu u Sagnac-ovoj konfiguraciji. Izvor stabilno generira koincidentne parove polarizacijski spregnutih fotona.

Iako je kvantno sprezanje fotona poznato, ovaj kontraintuitivni efekt i dalje je predmet intenzivnog istraživanja kako na fundamentalnoj tako i na razini mogućih primjena u kvantnoj komunikaciji, kvantnom računanju i kvantnoj metrologiji. Ostvareni rezultat je ključan za buduća istraživanja ove grupe.

Arbitrarily exhaustive generation of contextual sets

Recently obtained results published in Pavičić, M., Arbitrarily exhaustive hypergraph generation of 4-, 6-, 8-, 16-, and 32-dimensional quantum contextual sets, Physical Review A, 95, 06212–1-25 (2017) will be implemented in a series of experiments in the CEMS Research Unit Photonics and Quantum Optics.

Quantum contextuality is a property of quantum systems not to have predetermined values of their observables, in contrast to classical systems. Take an entangled photon pair. Each of the photons is genuinely unpolarized before we let them through polarizers.  After polarizers, measurements find the photons in definite polarization states. Can we assume that these polarizations were somehow predetermined when the pair was created? The so-called contextual sets of states of photons prove that we cannot. Such sets are not of just of a foundational theoretical interest. Recently, it turned out that the “contextuality is the source of a quantum computer’s power” (Nature; cited in the paper). Therefore, it is important for future applications and implementations to find new classes, instances, and structure of contextual sets as well as to design algorithms and programs for obtaining them. In this paper, arbitrary exhaustive hypergraph-based generation of the most explored contextual sets, Kochen-Specker (KS) ones, is carried out in up to 32 dimensions.

Twelve classes of critical KS sets (the ones that cannot be simplified further) are generated and analyzed, huge number of novel types and instances of them obtained and numerous properties of theirs found. Several thousand times more types and instances of KS sets than previously known are generated. All KS sets in three of the classes and in the upper part of a fourth are novel. The generation was carried out with the help of McKay-Megill-Pavičić (MMP) hypergraph language, algorithms, and programs which generate KS sets (see the feature image for two hypergraphs of 8-dim KS sets; also the figure below) strictly following their definition from the Kochen-Specker theorem, which itself celebrates semicentennial this year. This is in contrast to parity proof based algorithms which prevail in the literature and for which the majority of KS sets and even a whole KS class (as the one shown in the Figure below) are simply invisible.

Priopcenje za javnost povodom opstruiranja financiranja iz EU fondova od strane MZOS-a

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PRIOPĆENJE ZA JAVNOST Zagreb, 7. lipnja 2016.

Otvoreno pismo ministru znanosti, obrazovanja i sporta Predragu Šustaru:

Opstruiranjem financiranja iz EU fondova hrvatskih znanstvenih centara izvrsnosti ugrožava se 50 milijuna eura iz strukturnih fondova i radna mjesta za hrvatske znanstvenike – traži se hitna reakcija ministra Šustara!

Pedeset milijuna eura, upitna radna mjesta za čak tri stotine doktoranada i postdoktoranada, te riskiranje penala od Europske komisije, samo su dio crne statistike koja ozbiljno prijeti Republici Hrvatskoj (RH), a odvija se u sjeni problema s kurikularnom reformom.

Deset znanstvenih centara izvrsnosti proglašenih od strane Ministarstva znanosti obrazovanje i sporta (MZOS) tijekom 2014. i 2015. godine na prijedlog Nacionalnog vijeća za znanost, visoko obrazovanje i tehnološki razvoj, posljednjih su nekoliko mjeseci postalo taocem MZOS-a.

Naime, RH se strateški odredila kroz Operativni program (OP) za financiranje Znanstvenih centara izvrsnosti (2014 – 2020), te se prema Operativnom programu očekuje 50 milijuna eura iz Europskog fonda za regionalni razvoj (ERDF) koji bi bili na raspolaganju proglašenim centrima.

Kako bi centri mogli iskoristiti europska sredstva, MZOS je obvezan raspisati natječaj. Prvi indikativni rok za raspisivanje natječaja bio je 31. ožujka, te je pomaknut na 1. lipnja 2016., a natječaj još nije raspisan.

Unatoč brojnim službenim molbama za poštivanjem obveza koje su voditelji Znanstvenih centara izvrsnosti posljednjih mjeseci dostavili ministru Šustaru i premijeru Oreškoviću s upozorenjem da je RH preuzela obvezu te je dužna raspisati planirani natječaj iz strukturnih fondova u sklopu kojih bi se izvršila evaluacija planiranih troškova u okviru pojedinih centara, s današnjim datumom MZOS još uvijek nije aktivirao natječaj Europskog fonda za regionalni razvoj (ERDF) koji bi omogućio povlačenje čak 50 milijuna eura za Znanstvene centre izvrsnosti. Time se ozbiljno ugrožava realizacija znanstvenih aktivnosti proglašenih ZCI-a i gubitak 50 milijuna eura iz EU te zapošljavanje 300 mladih stručnjaka.

Podsjetimo, MZOS je proglasio Znanstvene centre izvrsnosti iz područja prirodnih, biomedicinskih, biotehničkih i tehničkih znanosti nakon zahtjevnih kriterija javnog natječaja, uključujući opsežne domaće i međunarodne recenzije i intervjue s voditeljima predloženih centara koji su proveli Agencija za znanost i visoko obrazovanje (AZVO) i Nacionalno vijeće za znanost, visoko obrazovanje i tehnološki razvoj. MZOS je potom temeljem članka 29. stavka 2. Zakona o znanstvenoj djelatnosti i visokom obrazovanju (Narodne novine, broj: 123/2003, 105/2004, 174/2004, 2/2007 – Odluka Ustavnog suda Republike Hrvatske, 46/2007, 45/2009,63/2011,94/2013, 139/13 i 101/2014 – Odluka i Rješenje Ustavnog suda Republike Hrvatske) proglasilo znanstvene centre izvrsnosti RH, čiji su članovi izvrsni hrvatski znanstvenici, među nositeljima međunarodne prepoznatljivosti hrvatske znanosti.

Proces prijave, vrednovanja i odabira centara trajao je tri godine, a Vlada RH je nakon provedenog postupka recenzija uskladila program centara s nacionalnim prioritetima i oni su u skladu sa Strategijom pametne specijalizacije (S3). Ovu Strategiju su više od dvije godine izrađivali brojni eksperti iz javnog i privatnog sektora koji se bave istraživanjem i razvojem, te ju je usvojio Hrvatski sabor i Europska komisija za znanost.

Cilj proglašenja centara je bio omogućiti izvrsnim hrvatskim znanstvenicima i institucijama uvjete za vrhunski istraživački rad kroz stabilno i pojačano financiranje te edukaciju mladih znanstvenika i značajan doprinos gospodarstvu RH.

Slijedom navedenog, proizlazi da se nepoštivanjem zadanih obveza od strane MZOS-a te neprovođenjem preuzetih obveza direktno ugrožavaju nacionalni interesi.

Nažalost, jedan od glavnih protivnika ustroja hrvatskih centara izvrsnosti, kao i od strane Europske komisije usvojene pametne specijalizacije (S3) RH, a koja je jedan od glavnih preduvjeta za povlačenje sredstava iz strukturnih fondova, je pomoćnik ministra za znanost dr. sc. Krešimir Zadro.

Poštovani ministre Šustar, otvorenim pismom javnosti obraćamo Vam se ispred svih Znanstvenih centara izvrsnosti (ZCI) iz područja prirodnih, biomedicinskih, biotehničkih i tehničkih znanosti sa zahtjevom da se javno očitujete o razlozima nepoštivanja odluka Vlade RH i neprovođenju usvojenih programa financiranja hrvatskih centara izvrsnosti iz EU fondova te datumu raspisivanja natječaja kako bi se izbjegao crni scenarij.

Vjerujemo da niste spremni potpuno ignorirati izvrsne hrvatske znanstvene skupine i propustiti priliku da se kroz usvojeni program pametne specijalizacije povuku sredstva u iznosu od 50 milijuna eura iz strukturnih fondova.

U situaciji kad se domaća sredstva za znanost i istraživanje sustavno režu, kad se događa egzodus najboljih mladih obrazovanih stručnjaka, znanstvena istraživanja i inovacije preživljavaju velikim dijelom zbog izvrsnosti istraživačkih skupina i velikih napora znanstvenika u povlačenju sredstva iz programa Europske unije, ovakvo opstruiranje rada Znanstvenih centara izvrsnosti da osiguraju europska sredstva za rad i zapošljavanje stručnog kadra je nedopustivo!

S poštovanjem,
voditelji proglašenih Znanstvenih centara izvrsnosti (STEM područja):

Znanstveni centar izvrsnosti za napredne materijale i senzore,
Institut Ruđer Bošković i Institut za fiziku, Zagreb

Dr. sc. Milko Jakšić – Milko.Jaksic@irb.hr
Dr. sc. Mile Ivanda – Mile.Ivanda@irb.hr
Dr. sc. Mario Stipčević – Mario.Stipcevic@irb.hr
Dr. sc. Marko Kralj – mkralj@ifs.hr

Znanstveni centar izvrsnosti za reproduktivnu i regenerativnu medicinu,

Medicinski fakultet, Sveučilište u Zagrebu,
Akademik prof. dr.sc. Slobodan Vukičević – slobodan.vukicevic@mef.hr
Prof. dr. sc. Davor Ježek – davor.jezek@mef.hr

Znanstveni centar izvrsnosti za virusnu imunologiju i cjepiva,
Medicinski fakultet, Sveučilište u Rijeci
Prof. dr. sc. Stipan Jonjić – stipan.jonjic@medri.uniri.hr

Znanstveni centar izvrsnosti za znanost i tehnologiju – STIM, Sveučilište u Splitu
Prof. dr. dr. h.c. Vlasta Bonačić-Koutecky – vbk@cms.hu-berlin.de

Znanstveni centar izvrsnosti za bioraznolikost i molekularno oplemenjivanje bilja, Agronomski fakultet , Sveučilište u Zagrebu
Prof. dr. sc. Zlatko Šatović – zsatovic@agr.hr

Znanstveni centar izvrsnosti za bioprospecting mora
Institut Ruđer Bošković, Zagreb
Dr.sc. Rozelindra Čož-Rakovac – Rozelindra.Coz-Rakovac@irb.hr

Znanstveni centar izvrsnosti za kvantne i kompleksne sustave te reprezentacije Liejevih algebri, Prirodoslovno-matematički fakultet, Sveučilište u Zagrebu

Prof.dr.sc Hrvoje Buljan – hbuljan@phy.hr
Prof. dr. sc. Pavle Pandžić – pandzic@math.hr

Znanstveni centar izvrsnosti za personaliziranu brigu o zdravlju,

Sveučilište Josip Juraj Strossmayer u Osijeku
Prof. dr. sc. Gordan Lauc – glauc@pharma.hr
Prof. dr. sc. Ines Drenjančević – ines.drenjancevic.peric@mefos.hr

Znanstveni centar izvrsnosti za temeljnu, kliničku i translacijsku neuroznanost, Medicinski fakultet, Sveučilište u Zagrebu
Prof. dr. sc. Miloš Judaš – mjudas@hiim.hr

Znanstveni centar izvrsnosti za znanost o podatcima i kooperativne sustave, Fakultet elektrotehnike i računarstva, Sveučilište u Zagrebu

Prof.dr.sc. Sven Lončarić – sven.loncaric@fer.hr
Prof. dr. sc. Ivan Petrović – ivan.petrovic@fer.hr

Priopćenje voditelja proglašenih
            Znanstvenih centara izvrsnosti (STEM područja)             ___________________________________________________________________________________________________

Physics of the Dark Universe Paper “KWISP: An ultra-sensitive force sensor for the Dark Energy sector”

One of the remaining puzzles in physics is the composition of the Universe. Now days we believe that it is made of about 5% ordinary matter, 25% dark matter and 70% of dark energy. Our knowledge about the nature of the dark constituents of the Universe is very feeble. They were introduced to explain some observational data. In particular the dark energy was introduced to explain the observed acceleration in the expansion rate of the Universe. One of the possible mechanisms would be the existence of a light scalar field. To render it compatible with General Relativity in the solar system and “fifth force” searches on Earth they have to be screened. One possibility is a so called “chameleon” mechanism which renders their effective mass dependent on the local matter density. In case they exist they can be produced in the Sun and detected on Earth by a suitable sensor. The detection mechanism relies on the equivalent of the radiation pressure, where solar chameleons impinge on a mobile surface and transfer momentum to it which displaces it from the equilibrium position.

CERN_Courier

Such a sensor has been built and tested in cooperation with the optics laboratory at INFN Trieste where the sensor was situated before transferring it to the final setup at CERN which was noted in the CERN Courier article (see picture). It is based on a thin silicon nitride micro-membrane placed inside a Fabry–Perot optical cavity. By monitoring the cavity characteristic frequencies it is possible to detect the tiny membrane displacements caused by an applied force. Its application to experiments in the Dark Energy sector, such as those for Chameleon-type WISPs, is particularly attractive, as it enables a search for their direct coupling to matter. The sensitivity and the absolute force calibration are given in the article published in the journal Physics of the Dark Universe (impact factor 8.57).

 

Projects

Projects

7. “Feasibility Study for employing the uniquely powerful ESS linear accelerator to generate an intense neutrino beam for leptonic CP violation discovery and measurement (ESSnuSB)“, leader for Croatia: B. Kliček. Project No.  777419 (H2020), signed: 22.11.2017., started: 01.01.2018. Financed through Horizon 2020.

6. “Support for top-level research of Centre of excellence for advanced materials and sensing devices“, leaders M. Jakšić, M. Ivanda, M. Kralj, and M. Stipčević. Funded through European structural and 5nvestment funds (ESIF), MSE grant No. KK.01.1.1.01.0001

5. “Quantum entanglement for ultra-secure communications“, Leaders: Dr. Mario Stipčević, (CEMS-IRB, Zagreb, Croatia) and Prof. dr. Rupert Ursin (IQOQI, Vienna, Austria). Duration: 2016-2017 (2 years).

In this project we address scientific and technological aspects of quantum entanglement which lies in the heart of the secure information exchange, quantum cryptography, random number generation as well as some vibrant scientific research topics related to quantum information and secure communications.

4. “Holography and interferometry under weak illumination” HrZZ – IP-2014-09-7515, 01.05.2015. – 30.04.2019. Leader: Nazif Demoli, Institute of Physics (IF). Associates: Hrvoje Skenderović (IF), Davorin Lovrić (IF), Jadranko Gladić (IF), Mario Rakić (IF), Mario Stipčević (RBI), Ognjen Milat (IF), Mladen Pavičić, Denis Abramović (IF), Marin Karuza (University of Rijeka). Research areas: Optical physics.

3. “TRANSHOW1 Knowledge transfer“, leader M. Lončarić.

2. “ICT COST Action IC1306 Cryptography for Secure Digital Interaction“, Leader: Prof. Claudio Orlandi (Aarhus University, Denmark), Coordinator for Croatia: Dr. Mario Stipčević, Ruđer Bošković Institute.

1. “ICT COST Action CA15220 Quantum Technologies in Space“, Leader: Prof. Angelo Bassi (University of trieste, Italy), Coordinator for Croatia: Dr. Mario Stipčević, Ruđer Bošković Institute.

Sci Reports published paper on optical quatnum random number generator

On-Demand Optical Quantum Random Number Generator with Ultra-Fast Response

The study was published by online journal Scientific Reports (IF 5.578) of the Nature Publishing Group.

Mario Stipčević from the Ruđer Bošković Institute (RBI) and his colleague Rupert Ursinfrom the Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, developed a new model of a quantum random number generator (QRNG). This device provides an ultra-fast response upon a bit request (9.8 ns) with 100 percent efficiency upon the trigger, and in-future-of-request random action. None of the generators or generating principles known so far satisfied all those requirements simultaneously to that extent.

On-Demand Optical Quantum Random Number Generator with Ultra-Fast Response

The device works on the principle similar to a coin toss bearing in mind that the process of flipping and reading a coin takes a very short time and the coin never flips away from your hands. With a given state of technology this new QRNG could be reduced to the size of the chip, which would open opportunities for a wide range of applications. This study was published by online journal Scientific Reports (IF 5.578) of the Nature Publishing Group.

Digital data processing in computers, mobile devices or ATM machines has a huge impact on our modern information-based society. Random numbers are essential for cryptographic protocols which are necessary to ensure security, privacy and integrity of communicated data.

Random number generators are essential components for a wide range of applications such as: cryptographic data protection, scientific research, simulations, or real and virtual casinos and online games. For example, in security systems they provide secret keys or tokens for authentications and encryption. They are commonly classified by the source of their randomness.

Unlike frequently used pseudo-random generators, physical random number generators do not depend on complex algorithms, but rather on a physical process to provide true randomness, which means that physical random numbers generators derive random numbers from a physical source of reasonably random process e.g. flipping a coin. This makes them more reliable, since their behaviour could not be replicated in a reasonable amount of time as in the case of pseudo-random generators.

”However, our primary motivation in this study was solving the fundamental problems of quantum entanglement.” – explained Stipčević, a senior research associate in the RBI Laboratory for electromagnetic and weak interactions and Head of the Research Unit for Photonics and Quantum Optics of the Center of Excellence for Advanced Materials and Sensors (CEMS).

MStipcevic - RUrsin

In this paper titled: “An On-Demand Optical Quantum Random Number Generator with In-Future Action and Ultra-Fast Response” the scientists presented a conceptually simple implementation, which offered a 100 percent efficiency of producing a random bit upon a request and simultaneously exhibited an ultra-low latency.

”We presented a novel type of QRNG which randomness can be obtained by suitable tuning the device controllable parameters in function of the hardware imperfections. It is unique in simultaneously satisfying three characteristics: a very short latency between the random bit request signal and the moment when the bit is generated, all physical processes relevant to generation of a bit happen after the request signal and with a 100 percent efficiency of producing a bit upon a request.

On top of that, we estimated deviation of the QRNG from perfect randomness and demonstrated that generated sequences of random bits pass NIST Statistical Test Suite (STS)1 without post-processing.” – concluded Stipčević and Ursin.

Talks and Publications

Articles in journals indexed in Current Contents:

  1. N. Agafonova et al. (OPERA Collaboration), “Final Results of the OPERA Experiment on nutau Appearance in the CNGS Neutrino Beam”, Phys. Rev. Lett. 120, 211801 (2018). DOI: 10.1103/PhysRevLett.120.211801
  2. S. K. Joshi, J. Pienaar, T. Ralph, L. Cacciapuoti, W. McCutcheon, J. Rarity, D. Giggenbach, J. G. Lim, V. Makarov, I. Fuentes, T. Scheidl, E. Beckert, M. Bourennane, D. E. Bruschi, A. Cabello, J. Capmany, A. Carrasco-Casado, E. Diamanti, M. Dusek, D. Elser, A. Gulinatti, R. Hadfield, T. Jennewein, R. Kaltenbaek, M. Krainak, H-K. Lo, C. Marquardt, G. Milburn, M. Peev, A. Poppe, V. Pruneri, R. Renner, C. Salomon, J. Skaar, N. Solomos, M. Stipčević, J. Torres, M. Toyoshima, P. Villoresi, I. Walmsley, G. Weihs, H. Weinfurter, A. Zeilinger, M. Zukowski, R. Ursin, “Space QUEST mission proposal: experimentally testing decoherence due to gravity”, New. J. Phys. 108028.R1 (2018) DOI: 10.1088/1367-2630/aac58b
  3. A. W. Ziarkash, S. K. Joshi, M. Stipčević, and R. Ursin, ”Comparative study of afterpulsing behavior and models in single photon counting avalanche photo diode detectors”, Scientific Reports 8, 5076:1-8 (2018). DOI: 10.1038/s41598-018-23398-z
  4. M. Jelovica, P. Grbčić, M. Mušković, M. Sedić, S.K. Pavelić, M. Lončarić, N. Malatesti, “In Vitro Photodynamic Activity of N-Methylated and N-Oxidised Tripyridyl Porphyrins with Long Alkyl Chains and Their Inhibitory Activity in Sphingolipid Metabolism”, Chem. Med. Chem. 13, 360–372 (2018). DOI: 10.1002/cmdc.201700748
  5. N. Agafonova et al., OPERA Collaboration, “Study of charged hadron multiplicities in charged-current neutrino–lead interactions in the OPERA detector”, OPERA Collaboration (N. Agafonova et al.), Eur. Phys. J. C78 (2018) 62:1-8. DOI: 10.1140/epjc/s10052-017-5509-y
  6. M. Pavičić, “Can Two-Way Direct Communication Protocols Be Considered Secure?,” Nanoscale Research Letters, 12:552 (2017). DOI: 10.1186/s11671-017-2314-3
  7. M. Pavičić, O. Benson, A. W. Schell, and J. Wolters, “Mixed basis quantum key distribution with linear optics,” Opt. Express 25(20), 23545-23555 (2017). DOI: 10.1364/OE.25.023545
  8. M. Stipčević, B. G. Christensen, P. G. Kwiat, D. J. Gauthier, “An advanced active quenching circuit for ultra-fast quantum cryptography”, Opt. Express 25, 21861-21876 (2017) DOI: 10.1364/OE.25.021861
  9. M. Pavičić, “Arbitrarily exhaustive hypergraph generation of 4-, 6-, 8-, 16-, and 32-dimensional quantum contextual sets,” Phys. Rev. A 95, 062121-1-25 (2017). DOI:  10.1103/PhysRevA.95.062121
  10. V. Anastassopoulos, …, M. Karuza, … (CAST Collaboration), “New CAST limit on the axion–photon interaction”, Nature Physics 13, 584–590 (2017). DOI: 10.1038/nphys4109
  11. M. Stipčević, N. Demoli, H. Skenderović, M. Lončarić, A. Radman, J. Gladić, and D. Lovrić, “Effective procedure for determination of unknown vibration frequency and phase using time-averaged digital holography”, Opt. Express 25, 10241-10254 (2017). DOI: 10.1364/OE.25.010241
  12. N. Malatesti, A. Harej, S. K. Pavelić, M. Lončarić, H. Zorc, K. Wittine, U. Anđelković, Đ. Josić, “Synthesis, characterisation and in vitro investigation of photodynamic activity of 5-(4- octadecanamidophenyl)-10, 15, 20-tris(N- methylpyridinium-3-yl)porphyrin trichloride on HeLa cells using low light fluence rate”, Photodiagnosis Photodyn Ther., 15, 115-126 (2016). DOI: 10.1016/j.pdpdt.2016.07.003
  13. M. Pavičić, “Classical Logic and Quantum Logic with Multiple and Common Lattice Models,” Adv. Math. Phys. 2016, 6830685 (2016). DOI: 10.1155/2016/6830685
  14. M. Karuza, G. Cantatore, A. Gardikiotis, D.H.H. Hoffmann, Y.K. Semertzidis, K. Zioutas, “KWISP: An ultra-sensitive force sensor for the Dark Energy sector”, Phys. Dark Universe 12,100–104(2016). DOI: 10.1016/j.dark.2016.02.004
  15. M. Stipčević, “Quantum random flip-flop and its applications in random frequency synthesis and true random number generation”, Rev. Sci. Instrum. 87, 035113 (2016). DOI: 10.1063/1.4943668
  16. M. Pavičić, “Deterministic mediated superdense coding with linear optics”, Phys. Lett. A 380, 848–855 (2016). DOI:  10.1016/j.physleta.2015.12.037
  17. N. Demoli, H. Skenderović, M. Stipčević, “Time-averaged photon-counting digital holography”, Opt. Lett. 40, 4245-4248 (2015). DOI: 10.1364/OL.40.004245
  18. M. Stipčević, R. Ursin, “An On-Demand Optical Quantum Random Number Generator with In-Future Action and Ultra-Fast Response”, Scientific Reports 5, 10214:1-8 (2015). DOI: 10.1038/srep10214
  19. M. Stipčević, J. Bowers, “Spatio-temporal optical random number generator”, Opt. Express 23, 11619-11631 (2015). DOI: 10.1364/OE.23.011619
  20. G. Humer, M. Peev, C. Schaeff, S., M. Stipčević, R. Ursin, “A simple and robust method for estimating afterpulsing in single photon detectors”, J. Lightwave Technol. 33, 3098-3107 (2015). DOI: 10.1109/JLT.2015.2428053
  21. N. Demoli, H. Skenderović, and M. Stipčević, “Digital holography at light levels below noise using a photon-counting approach”, Opt. Lett. 39, 5010–5013 (2014). DOI: 10.1364/OL.39.005010
  22. M. Stipčević, D. Wang, and R. Ursin, “Characterization of a commercially available large area, high detection efficiency single-photon avalanche diode”, IEEE J. Lightwave Technol. 31, 3591-3596 (2013). DOI: 10.1109/JLT.2013.2286422
  23. M. Pavičić, “In Quantum Direct Communication an Undetectable Eavesdropper Can Always Tell Ψ from Φ Bell States in the Message Mode,” Phys. Rev. A 87 , 042326-1-7 (2013). DOI: 10.1103/PhysRevA.87.042326
  24. N. Megill and M. Pavičić, “Kochen-Specker Sets and Generalized Orthoarguesian Equations,” Ann. Henri Poincare 12, 1417-1429 (2011). DOI: 10.1007/s00023-011-0109-0
  25. M. Pavičić, N. Megill, P. K. Aravind, and M. Waegell, “New class of 4-dim Kochen-Specker sets,” J. Math. Phys. 52, 022104-1-9 (2011). DOI: 10.1063/1.3549586
  26. Stipčević M., Skenderović H., Gracin D., “Characterization of a novel avalanche photodiode for single photon detection in VIS-NIR range”, Opt. Express 18,17448-17459 (2010). DOI: 10.1364/OE.18.017448
  27. M. Pavičić, B. D. McKay, N. Megill, and K. Fresl, ” Graph Approach to Quantum Systems,” J. Math. Phys. 51, 102103-1-31 (2010). DOI: 10.1063/1.3491766
  28. M. Pavičić, N.D. Megill, and J.-P. Merlet, “New Kochen-Specker Sets in Four Dimensions,” Phys. Lett. A 374, 2122-2128 (2010). DOI: 10.1016/j.physleta.2010.03.019
  29. M. Stipčević, “Active quenching circuit for single-photon detection with Geiger mode avalanche photodiodes”, Appl. Opt. 48, 1705-1714 (2009). DOI: 10.1364/AO.48.001705
  30. M. Stipčević, B. Medved Rogina, “Quantum random number generator based on photonic emission in semiconductors”, Rev. Sci. Instrum. 78, 045104:1-7 (2007). DOI: 10.1063/1.2720728
  31. M. Stipčević, “Fast nondeterministic random bit generator based on weakly correlated physical events”, Rev. Sci. Instr. 75, 4442-4449(2004). DOI: 10.1063/1.1809295

Books or chapters in books:

  1. M. Stipčević, and Ç. K. Koç, “True Random Number Generators”, in “Open Problems in Mathematics and Computational Science”, Koç, Çetin Kaya (Ed.), pp 275-315 Springer 2014, ISBN 978-3-319-10683-0, URL: http://www.springer.com/gp/book/9783319106823

Talks at international conferences:

  1. Pavičić, M., “Can Two-Way Direct Communication Protocols Be Considered Secure? (Invited Talk), EMN Meeting on Quantum, June 18-22 2017, Vienna, Austria; Program & Abstracts;   Abstract of the paper (A25): pp. 48-99; PPT Presentation; Recorded talk on Youtube.
  2. Megill, N.D. and Pavičić, M., “New Classes of Kochen-Specker Contextual Sets” (Invited Talk), MIPRO 2017,  The 40th International Convention on Information and Communication Technology, Electronics, and Microelectronics (IEEE Xplore Digital Library), May 22-26, 2017, Opatija, Croatia, Proceedings of The 40th International Convention on Information and Communication Technology, Electronics, and Microelectronics, May 22-26, 2017, Publisher: Institute of Electrical and Electronics Engineers (IEEE), POD Publ: Curran Associates, Inc., Red Hook, NY 12571 USA (2017); PPT presentation – Presented by M. Pavičić; Recorded talk on Youtube.
  3. Pavičić, M., “Massive Generation of Contextual Quantum Sets” (Invited Talk), EMN Meeting on Quantum Communication and Quantum Imaging-2016, August 23-26, 2016, Berlin, Germany; pp. 28-29. Web stranica;  Recorded talk on Youtube; Programme and abstracts.
  4. M. Karuza, “KWISP : the radiation pressure sensor”, Identification of Dark Matter 2016, IDM2016,  London 18-22 July 2016.
  5. Demoli, N., Skenderović, H., Stipčević, M. and Pavičić, M. “Photon Counting Digital Holography” (Invited Talk), Proc. SPIE 9890, Optical Micro- and Nanometrology VI, 989003-1-6, May 3, 2016
  6. N. Demoli, “Time-averaged holography using Photon-counting approach” (Invited Talk), Imaging and Applied Optics Congress, 25-28 July 2016, Heidelberg, Germany. DOI: 10.1364/DH.2016.DT2E.1
  7. M. Stipčević, B. G. Christensen, P. G. Kwiat, and D. J. Gauthier, “Advanced active quenching circuits for single-photon avalanche photodiodes” (Invited Talk), SPIE  Defense and Commercial Sensing 2016, Baltimore, Maryland, USA, April 17-21, 2016. DOI: 10.1117/12.2227999
  8. D. J. Gauthier, C. F. Wildfeuer, H. Guilbert, M. Stipčević, B. Christensen, D. Kumor, P. G. Kwiat, T. Brougham, S. M. Barnet, “Quantum Key Distribution Using Hyperentangled Time-Bin States”, Invited lecture, Proc. CQO X and QIM 2 2013, 17-20 June 2013, Rochester, NY, USA. DOI: 10.1364/QIM.2013.W2A.2

Teaching:

  1. N. Demoli, “Optics and holography”, Faculty of natural sciences, University of Zagreb, Croatia.
  2. M. Karuza, “Advanced electrodynamics”, “Structure of matter (lab.)”, and “Experimental methods in physics “, University of Rijeka, Croatia.
  3. M. Lončarić, “Laboratorijske vježbe iz geometrijske optike” and  “Laboratorijske vježbe iz fizikalne optike”, University of Applied Sciences Velika Gorica, Velika Gorica, Croatia

Invited seminars:

  1. M. Stipčević, “Photon detectors, quantum randomness, random flip-flops and their use in ICT security and hyper computation”, May 4, 2016, Special seminar of SEAS hosted by prof. M. Loncar at Harvard SEAS, Lexington, MA, USA. (flyer)
  2. M. Stipčević, “Photon detectors, quantum randomness and their applications in ICT security”, February 19, 2016, Invited seminar hosted by dr. S. Verghese at MIT Lincoln Labs, Lexington, MA, USA.
  3. M. Pavičić,”Two-Way Deterministic Communication Is Like Sending Plain Text under Quantum Protection”, Special Colloquium held at the Department of Physics-Nanooptics, Faculty of Mathematics and Natural Sciences, Humboldt University of Berlin, Germany, on 07.10.2016; Recorded talk on Youtube
  4. M. Stipčević, “Quantum random flip-flop: a novel device for digital and analog signal processing”, March 10, 2015. Invited seminar hosted by Prof. J. E. Bowers, Electrical and computer engineering, University of California Santa Barbara, Santa Barbara, USA (web page)
  5. M. Pavičić, “High-Efficiency Source of Heralded Down-Converted Separated Photons in Arbitrary Bell States”, Colloquium held at Humboldt University of Berlin, Institut for Physics, Germany, on 15.07.2015 (flyer)

Other talks:

  1. M. Stipčević, “Light and us”, popular lecture given at Elementary School V. Kaleba, Tisno, Croatia. download
  2. M. Lončarić, “Neka bude svjetlost”, Seminar u okviru sastanka Nastavne sekcije Hrvatskog fizikalnog društva održanog 2. lipnja 2016 u Zagrebu.
  3. M. Stipčević, “Svjetlost i fenomen kvantnog sprezanja”, predavanje u povodu Međunarodne godine svjetla u Hrvatskoj akademiji znanosti i umjetnosti 30.09.2015. download

Awards:

  1. In 2017,. M. Stipčević – Member of Editorial Board of Nature’s Scientific Reports
  2. In 2016., M. Stipčević –  Special award for outstanding contribution to the strengthening of scientific excellence and the reputation of Ruđer Bošković Institute
  3. In 2015., M. Stipčević – Outstanding reviewer for AIP Review of Scientific Instruments, Rev. Sci. Instrum. 86, 089801 (2015). DOI: 10.1063/1.4927606
  4. In 2015., M. Stipčević – IRB Director Award for 2015 in the category of encouraging competitive projects applied at HORIZON 2020 for the project “iSEQURE”.

Appearance in media:

  1. http://spectrum.ieee.org/nanoclast/computing/hardware/a-true-random-number-generator-built-from-carbon-nanotubes-promises-better-security-for-flexible-electronics
  2. http://www.irb.hr/eng/Highlights/On-Demand-Optical-Quantum-Random-Number-Generator-with-Ultra-Fast-Response
  3. http://www.irb.hr/Izdvojene-novosti/Fizicki-generator-slucajnih-brojeva-s-najbrzim-refleksima
  4. http://www.tportal.hr/gadgeterija/tehnologija/387238/Hrvat-osmislio-superbrzi-kvantni-generator-slucajnih-brojeva.html
  5. http://www.vidi.hr/Sci-Tech/Znanost/Novi-hrvatski-kvantni-generator-slucajnih-brojeva
  6. http://cudaprirode.com/portal/bpzn/11389-hrvati-razvili-kvantni-generator-sluajnih-brojeva
  7. http://www.narodni-list.hr/posts/117585006
  8. http://narod.hr/hrvatska/hrvatski-znanstvenik-u-timu-koji-je-razvio-fizicki-generator-slucajnih-brojeva-s-najbrzim-refleksima
  9. http://www.presscut.hr/Web%20Sharing%20ZON/02-2018/02-02-2018/Ve%C4%8Dernji%20list%20-%20Hrvatska/Presscut_17842332.pdf
  10. http://www.presscut.hr/Web%20Sharing%20ZON/02-2018/02-02-2018/Jutarnji%20list/Presscut_17842583.pdf
  11. http://www.presscut.hr/Web%20Sharing%20ZON/02-2018/02-02-2018/Poslovni%20dnevnik/Presscut_17842516.pdf
  12. https://www.hina.hr/vijest/9715949
  13. https://www.vecernji.hr/techsci/predstavljen-projekt-centra-izvrsnosti-za-napredne-materijale-i-senzore-vrijedan-38-milijuna-kn-1223602
  14. https://zimo.dnevnik.hr/clanak/predstavljen-projekt-zpotpora-vrhunskim-istrazivanjima-centra-izvrsnosti-za-napredne-materijale-i-senzore-vrijedan-38-milijuna-kuna—505301.html
  15. http://www.poslovnipuls.com/2018/02/01/predstavljen-projekt-potpora-vrhunskim-istrazivanjima-centra-izvrsnosti-za-napredne-materijale-i-senzore-vrijedan-38-milijuna-kuna/
  16. http://www.vidi.hr/Sci-Tech/Znanost/38-milijuna-kuna-hrvatskom-znanstvenom-centru-CEMS
  17. http://www.cropc.net/it-vijesti/dogadaji/8033-predstavljen-projekt-potpora-vrhunskim-istrazivanjima-centra-izvrsnosti-za-napredne-materijale-i-senzore-vrijedan-38-milijuna-kuna
  18. https://www.obavjestajac.hr/1229179/predstavljen-projekt-centra-izvrsnosti-za-napredne-materijale-i-senzore-vrijedan-38-milijuna-kn
  19. http://www.presscut.hr/webpartners/multilang/VIDEOTekst.asp?ID=3112535&Tip=Tekst&Partner_id=1491
  20. http://www.presscut.hr/webpartners/multilang/VIDEOTekst.asp?ID=3130924&Tip=Tekst&Partner_id=1491
  21. http://www.presscut.hr/webpartners/multilang/AudioTekst.asp?ID=3119328&Tip=Tekst&Partner_id=1491

Research topics

  1. Generating quantum coupled pairs of photons

G2D_scheme_LRAt RBI we have built an experimental setup for parametric down-conversion using home made laser wavelength of 405 nm. Photograph on the left shows cross-section of the light cones exiting the nonlinear BBO crystal.

Quantum entangled “Einstein-Podolsky-Rosen” (EPR) photon pairs are created at the intersections of the cones. For most of the planned research, we need much stronger source of energy-degenerated EPR pairs in order to fulfill the objectives of the proposed research in quantum holography, optical resonators, hyperentanglement, super fast quantum cryptography, random number generation, searching for hidden vector bosons, and so on. The preferred technical solution to EPR generation the current state of the art is to build a source in the VIS-NIR wavelength area, where our innovative detection technology achieves the best performance, by using the well known technique of periodically poled nonlinear optical crystals.

  1. Novel photon detectors and detector characterization methods

In our group we have a strong expertise in building single photon detectors based on avalanche photodiodes driven in the Geiger mode. We are active in developing innovative photon-counting techniques as well as in research of novel methods for characterization of photon detectors. The research conducted in CEMS-Photonics is oriented towards the study and use of quantum properties of individual photons, therefore almost all our experiments depend on the detection and counting of photons. To that end we almost exclusively use photon-counting detectors developed and optimized in our lab.

  1. Holography

The current situation in the field of holography is mainly the use of powerful laser source and a CCD camera to record the hologram. We plan to expand the holographic technology in two new directions: holography with individual photons and quantum holography, and for this we need a new type of positionally-resolution camera sensitive to individual photons.

While holography is used for recording and reconstruction of complex three-dimensional wave fronts, interferometry enables the analysis of static and dynamic changes in these wave fronts. Both techniques, holography and interferometry, have gone through several pathways. One route goes from classic to digital (replacing the photo-emulsion CCD sensors) which opened up new opportunities such as the production of digital holographic interferometric video film in color or vibration monitoring of modal structure in real time. Another development path goes towards recording a scene illuminated by fundamentally lowest intensity of light. In all these segments members of our group have made significant contributions. This second time, leading to ultra-low levels of light or to holography with individual photons and, for the moment hypothetical, quantum holography. Terms of ultra-low-level lighting impose particularly demanding laboratory needs such as special light sources, the matrix of the position-resolved detectors sensitive to individual photons, as well as laboratory space completely devoid of vibration and other disturbances. In return, new research directions could provide original theoretical developments, applications and inventions.

  1. Quantum cryptography and quantum communication

Quantum cryptography allows completely secure transfer of information between two points via a technique for growing a previously existing “small” shared key. Up to now has been proven that the security of quantum protocol guaranteed the laws of quantum physics and even under the assumption that they hold only approximately, ie. if our understanding of quantum physics is incomplete. Practical devices for quantum cryptography has already been commercialized (IqQuantitue, Switzerland and MagiQ, USA), but are currently far from the convenience and price that would allow for wider use. In order to obtain practical devices significant progress on fundamental and technological levels is required.

  1. Search for bosons of the hidden sector optical techniques

Hidden Sectors are groups of fundamental fields that act between them but have very little interaction with the visible world, are common ingredients theories that extend the standard model and strive for an explanation of its parameters and hierarchy. Fields in the Standard Model allows kinetic mixing between the Standard Model and the hidden (1) fields where the boson (now hypothetical) that belongs to the added U (1) group called parafotonom. There is a wealth of theoretical models that provide enough freedom to justify the existence of parafotons with any parameters that are allowed by experimental observations. Kinetic mixing provides a mechanism for the oscillation of photons in the light boson and back that can be used in experiments based on its weak interaction with the visible world. This type of experiment is generally called “the passage of light through the wall”. If the photon on one side of the wall turns into parafoton, he can pass unhindered through the opaque wall. On the other side of the wall, provided that the condition of the balance exceeds parafotons photons, in a suitable low-noise detector will be detected photon. Probability observations signal can be increased by several orders of magnitude using optical resonant cavities on both sides of the wall, which is the path of research which we started.

  1. Quantum randomness of quantum contextuality

Coincidence or randomness is an invaluable resource in many areas of scientific research and practical applications, especially in computer science and ICT security. The classic computer generated pseudo-random numbers that can be useful in some applications, they remain fundamentally deterministic and therefore, at least in principle, predictable detrimental to the security of cryptography. We have proven that quantum cryptography is impossible without local private random number generator or something equivalent that. There are several open issues related accident. Firstly, as of yet we have no definition of randomness. Then there is the question of what is the source of randomness in quantum physics, is there a true randomness or are there hidden variables?

Random Number Generators are one of the hot topics of research in the last decade. However the sharp discrepancy between the number of publications (83 patents per year in the last decade, in 1418 total, countless scientific articles) and the number of just five earned practical quantum random number generator that has ever appeared on shows clearly the conceptual and technical immaturity of this branch. In our opinion, the main problems are the lack of evidence of a coincidence and unrepeatable results. Our research will be directed towards the elimination of these problems.

Quantum randomness is also implicitly contained in quantum contextuality. Quantum contextuality is the property of a quantum system that any of its measurements has a value independent of other compatible measurements carried out at the same time. Hence, measurement results of quantum systems cannot in general have predetermined values and the sets that satisfy this quantum property are called Kochen-Specker (KS) sets. In this area, we already have significant theoretical results and we will continue theoretical and experimental research in this area.

The study of randomness and the principle of generating random numbers can easily result in new EU projects, inventions and cooperation with small and medium-sized enterprises (SMEs).

  1. Scalable quantum computing, contextual and quantum repeaters

Quantum computing is a hypothetical computer paradigm in whose practical realization researchers are working with increasing intensity in recent years. Our group is working on the development on algebraic formalism that could allow universal quantum computing using a direct translation of the standard formalism of Hilbert space to algebraic quantum protocols with built exponential acceleration of computation for certain special class of mathematical problems.