Posted on

November 2015: Few Photon Transport in Many-Body Photonic Systems: A Scattering Approach

With the help of two-photon scattering matrix of in- and out-states, we find that the use of quantum input states in photonic quantum simulators such as those implemented in coupled cavity arrays, allows one to observe not only stronger spectroscopic signals of the underlying strongly correlated states but also a faithful representation of their intensity-intensity correlations, as compared to the conventional classical driving fields. Our analysis can be applied for many-body spectroscopy of any many-body model amenable to a photonic quantum simulation,  including the Jaynes-Cummings-Hubbard, the extended Bose-Hubbard, and a whole range of spin models.

Authors

C. Lee, C. Noh, N. Schetakis,  D. G. Angelakis “Few photon transport in nonlinear cavity arrays:Probing signatures of strongly correlated states”, Phys. Rev. A 92, 063817 (2015).

Abstracts

We study the quantum transport of multiphoton Fock states in one-dimensional Bose-Hubbard lattices implemented in QED cavity arrays (QCAs). We propose an optical scheme to probe the underlying many-body states of the system by analyzing the properties of the transmitted light using scattering theory. To this end, we employ the Lippmann-Schwinger formalism within which an analytical form of the scattering matrix can be found. The latter is evaluated explicitly for the two-particle, two-site case which we use to study the resonance properties of two-photon scattering, as well as the scattering probabilities and the second-order intensity correlations of the transmitted light. The results indicate that the underlying structure of the many-body states of the model in question can be directly inferred from the physical properties of the transported photons in its QCA realization. We find that a fully resonant two-photon scattering scenario allows a faithful characterization of the underlying many-body states, unlike in the coherent driving scenario usually employed in quantum master-equation treatments. The effects of losses in the cavities, as well as the incoming photons’ pulse shapes and initial correlations, are studied and analyzed. Our method is general and can be applied to probe the structure of any many-body bosonic model amenable to a QCA implementation, including the Jaynes-Cummings-Hubbard model, the extended Bose-Hubbard model, as well as a whole range of spin models.

 

 

 

Posted on

July 2015: Quantum plasmonic excitation in graphene and loss-insensitive propagation

Authors:

G. W. Hanson, S. A. H. Gangaraj, C. Lee, D. G. Angelakis, M. Tame “Quantum plasmonic excitation in graphene and robust-to-loss propagation”, Phys. Rev. 92, 013828 (2015)

Abstract:

We investigate the excitation of quantum plasmonic states of light in graphene using end-fire and prism coupling. In order to model the excitation process quantum mechanically, we quantize the transverse-electric and transverse-magnetic surface plasmon polariton (SPP) modes in graphene. A selection of regimes are then studied that enable the excitation of SPPs by photons and we show that efficient coupling of photons to graphene SPPs is possible at the quantum level. Furthermore, we study the excitation of quantum states and their propagation under the effects of loss induced from the electronic degrees of freedom in the graphene. Here we investigate whether it is possible to protect quantum information using quantum-error correction techniques. We find that these techniques provide a robust-to-loss method for transferring quantum states of light in graphene over large distances.

Posted on

April 2015: Optical simulation of charge conservation violation and Majorana dynamics

“Forbidden physics has been seen in an experiment – sort of. CQT researchers and collaborators in Germany, Austria and India simulated with light the behaviour of an impossible particle known as a Majoranon…”
Read more from CQT highlight for non specialists, ” Light mimics forbidden particle “

This work was chosen for a focus article in Οptics & Photonics News (OPN)  “Using light to simulate unphysical particles”. ! It has also appeared in the Science Section, International Business Times, as well as phys.org  and sciencedaily

Authors

R. Keil, C. Noh, A. Rai, S. Stutzer, S. Nolte, D. G. Angelakis, A. Szameit “Experimental simulation of charge conservation violation and Majorana dynamics”, Optica 2,454 (2015)

Abstracts

Unphysical solutions are ruled out in physical equations, as they lead to behavior that violates fundamental physical laws. One of the celebrated equations that allows unphysical solutions is the relativistic Majorana equation, thought to describe neutrinos and other exotic particles predicted in theories beyond the standard model. The neutrally charged Majorana fermion is the equation’s physical solution, whereas the charged version is, due to charge nonconservation, unphysical and cannot exist. Here, we present an experimental scheme simulating the dynamics of a charged Majorana particle by light propagation in a tailored waveguide chip. Specifically, we simulate the free-particle evolution as well as the unphysical operation of charge conjugation. We do this by exploiting the fact that the wave function is not a directly observable physical quantity and by decomposing the unphysical solution to observable entities. Our results illustrate the potential of investigating theories beyond the standard model in a compact laboratory setting.

Posted on

News before 2015

December 2014: Our joint work with the groups of Hyunseok Jeong in Korea, and Tim Ralph in Australia, has been published in JOSA B 31, 3057. We investigate how to experimentally detect a recently proposed measure to quantify macroscopic quantum superpositions [Phys. Rev. Lett. 106, 220401 (2011)], namely, “macroscopic quantumness” I. Schemes based on overlap measurements for harmonic oscillator states and for qubit states are extensively investigated. Effects of detection inefficiency and coarse-graining are analyzed in order to assess feasibility of the schemes.

September 2014:  Jirawat  and Tian Feng graduates of Cavendish and DAMTP Cambridge joined the group as PhD students. Welcome guys!

August 2014:Dimitris has been nominated for the Management Committee of the EU COST Action “Nanoscale Quantum Optics” 2014-2018

MPNS COST Action MP1403Nanoscale Quantum OpticsCOST | European Cooperation in Science and Technology

The investigation of quantum phenomena in nanophotonics systems may lead to new scales of quantum complexity and constitutes the starting point for developing photonic technologies that deliver quantum-enhanced performances in real-world situations. This ambition demands new physical insight as well as cutting-edge engineering, with an interdisciplinary approach and a view towards how such groundbreaking technologies may be implemented and commercialized. The Action aims at promoting and coordinating forefront research in nanoscale quantum optics (NQO) through a competitive and organized network, which will define new and unexplored pathways for deploying quantum technologies in nanophotonics devices within the European research area. The main vision is to establish a fruitful and successful interaction among scientists and engineers from academia, research centers and industry, focusing on quantum science & technology, nanoscale optics & photonics, and materials science. The Action will address fundamental challenges in NQO, contribute to the discovery of novel phenomena and define new routes for applications in information & communication technology, sensing & metrology, and energy efficiency. Gathering a critical mass of experts the Action will serve as a platform in NQO and as such it will cooperate with industry and academia to promote innovation and education in a forefront research field.

July 2014:  Our work on “Probing the topological properties of the Jackiw-Rebbi model with light”  has been accepted in Nature Scientific Reports 4, 6110 (2014)

The Jackiw-Rebbi model describes a one-dimensional Dirac particle coupled to a soliton field and can be equivalently thought of as the model describing a Dirac particle with a spatially dependent mass term. Neglecting the dynamics of the soliton field, a kink in the background soliton profile yields a topologically protected zero-energy mode for the particle, which in turn leads to charge fractionalization. We show here that the model, in the first quantised form, can be realised in a driven slow-light setup, where photons mimic the Dirac particles and the soliton field can be implemented–and tuned–by adjusting optical parameters such as the atom-photon detuning.  Furthermore, we discuss how the existence of the zero-mode, and its topological stability, can be probed naturally by analyzing the  transmission  spectrum.  We conclude by analyzing the robustness of our approach against  possible experimental errors in engineering the Jackiw-Rebbi Hamiltonian in this optical setup.


(Left): Schematic diagram of the linear slow light system required. Lightis interfaced with an ensemble of  atoms where propagating light fields $\mathcal{E}_1$ and $\mathcal{E}_2$ play the role of Dirac spinor components. By adjusting the relevant optical couplings and detunings, the J-R model can be simulated and its topological aspects probed by looking at the transmission spectrum. (b) The reflection $|R|^{2}$ (black) and transmission $|T|^{2}$ (red) curves for the effective Dirac particle (a) without the soliton background and (b) with a soliton field whose profile is $0.25 \tanh(0.02 z)$. (a) shows the Dirac mass bandgap whereas (b) shows near-unity transmission near the zero-energy due to the bound zero-mode.

April 2013: Out  work on “Experimental simulation of charge conservation violation and Majorana dynamics” is out, for a preprint in pdf click arXiv:1404.5444

Unphysical particles are commonly ruled out from the solution of physical equations, as they fundamentally cannot exist in any real system and, hence, cannot be examined experimentally in a direct fashion. One of the most celebrated equations that allows unphysical solutions is the relativistic Majorana equation which might describe neutrinos and other exotic particles beyond the Standard Model. The equation’s physical solutions, the Majorana fermions, are predicted to be their own anti-particles and as a consequence they have to be neutrally charged; the charged version however (called Majoranon) is, due to charge non-conservation, unphysical and cannot exist. On

the other hand, charge conservation violation has been contemplated in alternative theories associated with higher spacetime dimensions or a non-vanishing photon mass; theories whose exotic nature makes experimental testing with current technology an impossible task. 

In our work, we experimentally implement a simulation of the Majorana equation and study the dynamics of its hypothetical particle solution, the Majoranon. For this we exploit the fact that in quantum mechanics the wave function itself is not a measurable quantity. Therefore, wave functions of real physical particles, in our case Dirac particles with opposite masses, can be superposed to a wave function of an unphysical particle, the Majoranon. In our experiment each Dirac particle is simulated by photon pulses propagating in specifically designed optical waveguide lattices reproducing the necessary relativistic dynamics. After a predefined evolution length the two lattices are recombined and the evolution of the Majoranon wave function can be inferred from measurable intensities of the output light. Input state preparation, evolution and read-out are all realised within one compact optical chip. We observe the strong impact of the charge conjugation operation on the dynamics of the simulated particle. In particular, we show that a characteristic quantity corresponding to the pseudo-energy of a Dirac-system behaves very differently in the Majorana-system: the latter displays a full-oscillation between the spinor components unlike the former.

Besides such specific observations of the exotic Majorana dynamics, our results represent the first implementation of a simulator for an unphysical phenomenon. We anticipate our findings to open the field of quantum simulation of exotic particles beyond the Standard Model and to substantially widen the scope of future investigations with respect to yet unknown benefits from unphysical operations in areas such as quantum information processing. 

March 2013:  Dimitris  has been invited to talk about  our work on quantum simulations with hybrid light-matter systems to the following international conferences. 

Control of Quantum Dynamics of Atoms, Molecules and Ensembles by Light Workshop 2014, Bulgaria, 23-27 June 2014

META’14, the 5th International Conference on Metamaterials, Photonic Crystals and Plasmonics, Singapore, 20-23 May.

Advanced Workshop on Landau-Zener Interferometry and Quantum Control in Condensed Matter, ICTP workshop, Smyrna, Turkey, 29 September-3 October

23rd Annual International Laser Physics Workshop, Sofia, Bulgaria July 14-18

February 2013 Our paper on “Probing the effect of interaction in Anderson localization using linear photonic lattices” has been published in Physical Review A

January 2014: Dimitris is invited to join the editorial board of European Physical Journal-Quantum Technology by Springer

December 2013:    Dr  Ping Nang Ma from ETH, joined our group as postdoctoral research fellow. Welcome  to the groupTama!

October 2013:      Special issue on “Quantum simulations”  in Springer EPJ Quantum Technology is accepting submissions! Guest edited by  D.G. Angelakis, D. Jaksch, A. Aspuru-Guzik and E. Solano. Topics include both theoretical and experimental aspects of quantum simulations. Accepting submissions now until June 1st 2014!
 
September 2013:   Coverage of our recent work in local and  national newpapers (in Greek)ΕΛΕΥΘΕΡΟΤΥΠΙΑ , ΕΦΗΜΕΡΙΔΑ ΤΩΝ ΣΥΝΤΑΚΤΩΝ,  ΧΑΝΙΩΤΙΚΑ

August 2013: Our works on “  Robust-to-loss entanglement generation using a quantum plasmonic nanoparticle array ”  and “Realizing the driven non-linear Schrodinger equation with stationary light” have been published in New Journal of Physics  and  accepted in Europhysics Letters.

June 2013: The Benasque workshop on Quantum Simulators 2013 is announced, Dimitris will be giving a invited talk, check here for the program details 

May 2013: Nikos has finished his first paper, a collaboration with Oxford on “Frozen photons in Jaynes-Cummings arrays”. arXiv:arXiv:1305.6576. Well done Nikos!

May 2013: MingXia, our first CQT PhD student,  has finished and submitted her PhD thesis on “Quantum simulations with photons in nonlinear optical waveguides”. Well done MingXia!

April 2013: Our work on “Proposal for simulating the Majorana equation in tabletop experiment has been published” as Phys. Rev. A Rapid, 87 040102.

 March 2013Invited session in APS March meeting 2013 in Baltimore on “Quantum Simulation with Photons” this year. Dimitris gave an invited talk and Changsuk, Changyoup, Amit and MingXia presented talks and posters on our recent works in this field. Check the program here 

March 2013: Our work Simulating neutrino oscillations in trapped ions” published at NJP 14 033028 (2012) has been selected for the “NJP Highlights of 2012” . When published last year, was  covered  in various science media: Phys.org “Dance  like  a  neutrino:  Quantum  scheme  to  simulate  neutrino  oscillations , Science news lineSPACEDAILYEurekalertFermilab. Check out the TUC research highlight 

February 2013. Our paper “Mimicking interacting relativistic theories with stationary pulses of light” has been published at PRL.  See abstract further down on check the journal  Phys. Rev. Lett. 110, 100502 (2013). Check out the Centre for Quantum Technologies research highlights

 

January 2013:  A multi-group proposal comprised by several CQT groups including ourselves, was awared  S$10 million for research into randomness!

Posted on

Short CV: Dimitris Angelakis

Research output

Dimitris Angelakis has been invited to deliver more 35  talks in international meetings including the annual American Physical Society meeting, the Quantum Simulations meetings in Benasque Spain and the ICTP workshops. He has also delivered more than 40 invited seminars in universities and research institutions worldwide. He has published around 50 papers,  with a total of more than  1700 citations and , Η=21, i10=29. He has organized and  edited the proceedings of a NATO ASI conference, a joint school and workshop in Quantum Simulations, a review article for IOP Reports in Progress in Physics,  and also edited a volume for Springer on quantum simulations with hybrid atom-photon systems. His work has been highlighted in the scientific media with articles n New ScientistNature Research Highlights,  The Innovation MagazinePhysics World and BIMA Science among others (see popular articles).

Funding and service

For his research activities, he has raised the equivalent of more than  2 million Euros in UK, Greece and Singapore and have evaluated research proposals for  the ERC Starting Grant scheme, European Young Investigator Award Scheme, the Netherlands Organization for Scientific Research and the  Swiss Research Council. He has also  served in various faculty committees in St Catharine’s College,-University of Cambridge, the Technical University of Crete and the Centre for Quantum Technologies Singapore. Recently he was invited to join the Management Committee of the of the EU COST Action “Nanoscale Quantum Optics”  representing Greece. He has  refereed for most physics journals including PRL, Nature, Science  and currently serves in the editorial board of  Springer EPJ Quantum Technology where he  also was the lead guest editor of a special issue on “Quantum Simulations” published in 2014.  He has successfully supervised  a number of MSc students, four postdoctoral scholars (two moved into faculty jobs straight after), one PhD student ( currently a postdoc in Oxford University) and currently advising three more PhDs and three postdocs.

 

Awards

Awards he has received include the “Institute of Physics, Quantum Electronics and Photonics Thesis Prize” in 2002 for the best PhD thesis in UK in the field if Quantum Electronics and Photonics, the  “St Catharine’s College Cambridge JRF in Physics” in 2001,  the “Valerie Myescrough  Prize 2000” for graduate students performance, and has been an IKY (Greek State Scholarship Foundation) scholar for the consecutive years 1993-1997 (undergraduate), and 1998-2001(postgraduate).

Personal: Born 3/11/1975 Chania, Greece. Married, three children