Dimitris G. Angelakis

Technical University of Crete

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Daniel Leykam

Singapore University of Technology and Design

Changsuk Noh

Kyungpook National University

Jirawat Tangpanitanon

National University of Singapore

L. C. Kwek

Nanyang Technological University

Sougato Bose

University College London

V. M. Bastidas

NTT Basic Research Laboratories

Mingxia Huo

Beijing Jingshida Electromechanical Equipment Research Institute

Amit Rai

Jawaharlal Nehru University

Supanut Thanasilp

École Polytechnique Fédérale de Lausanne

Dieter Jaksch

University of Oxford

Cooperative Institutions

Centre for Quantum Technologies

National University of Singapore

Google (United States)

University of California, Santa Barbara

University of California, Riverside

Imperial College London

University of Science and Technology of China

University of Oxford

Centre National de la Recherche Scientifique

Foundation for Research and Technology Hellas

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Photon-blockade-induced Mott transitions andXYspin models in coupled cavity arrays

Physical Review A (2007)

Dimitris G. Angelakis Marcelo F. Santos Sougato Bose

We propose a physical system where photons could exhibit strongly correlated effects. We demonstrate how a Mott-insulator phase of atom-photon excitations (polaritons) can arise in an array of individually addressable coupled electromagnetic cavities when each of these cavities is coupled resonantly to a single two-level system (atom, quantum dot, or Cooper pair). This Mott phase is characterized by the same integral number of net polaritonic excitations with photon blockade providing the required repulsion between the excitations in each site. Detuning the atomic and photonic frequencies suppresses this effect and induces a transition to a photonic superfluid. Finally, on resonance the system can straightforwardly simulate the dynamics of many-body spin systems.

Mott insulator

10.1103/physreva.76.031805

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Citations (541)

Photonic crystals and inhibition of spontaneous emission: an introduction

Contemporary Physics (2004)

Dimitris G. Angelakis P. L. Knight Emmanuel Paspalakis

Abstract In the first part of this introductory review we outline the developments in photonic band gap materials from the physics of photonic band gap formation to the fabrication and potential applications of photonic crystals. We briefly describe the analogies between electron and photon localization, present a simple model of a band structure calculation and describe some of the techniques used for fabricating photonic crystals. Also some applications in the field of photonics and optical circuitry are briefly presented. In the second part, we discuss the consequences for the interaction between an atom and the light field when the former is embedded in photonic crystals of a specific type, exhibiting a specific form of a gap in the density of states. We first briefly review the standard treatment (Weisskopf – Wigner theory) in describing the dynamics of spontaneous emission in free space from first principles, and then proceed by explaining the alterations needed to properly treat the case of a two-level atom embedded in a photonic band gap material. Acknowledgements DGA acknowledges Professor Artur Ekert for useful discussions and his support in the Cambridge CQC. EP and DGA would like to thank Professor Nikolaos Stefanou and Dr Vassilios Yannopapas for useful discussions in the area of photonic crystals. DGA also acknowledges St Catharine's College, University of Cambridge for financial support and the Cambridge MIT Institute for travel support. We acknowledge all the several groups that kindly allowed their photos and graphs to be used in these article. We also apologize if due to the introductory nature of this article, the limited space and the vastness of the corresponding literature in photonic crystals some groups with interesting contributions in the field might not have been mentioned.

Electronic band

10.1080/00107510410001676795

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Citations (40)

A single-interaction step implementation of a quantum search in coupled micro-cavities

EPL (Europhysics Letters) (2010)

Elica Kyoseva Dimitris G. Angelakis L. C. Kwek

We present a method for realizing efficiently Grover's search algorithm in an array of coupled cavities doped with three-level atoms. We show that by encoding information in the lowest two ground states of the dopants and through the application of appropriately tuned global laser fields, the reflection operator needed for the quantum search algorithm can be realized in a single physical operation. Thus, the time steps in which Grover's search can be implemented become equal to the mathematical steps ~ O(\sqrt{N}), where N is the size of the register. We study the robustness of the implementation against errors due to photon losses and fluctuations in the cavity frequencies and atom-photon coupling constants.

Robustness

Operator (biology)

Reflection

10.1209/0295-5075/89/20005

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Citations (10)

Explainable Natural Language Processing with Matrix Product States

Jirawat Tangpanitanon Chanatip Mangkang Pradeep Bhadola Yuichiro Minato Dimitris G. Angelakis

Despite empirical successes of recurrent neural networks (RNNs) in natural language processing (NLP), theoretical understanding of RNNs is still limited due to intrinsically complex non-linear computations. We systematically analyze RNNs' behaviors in a ubiquitous NLP task, the sentiment analysis of movie reviews, via the mapping between a class of RNNs called recurrent arithmetic circuits (RACs) and a matrix product state (MPS). Using the von-Neumann entanglement entropy (EE) as a proxy for information propagation, we show that single-layer RACs possess a maximum information propagation capacity, reflected by the saturation of the EE. Enlarging the bond dimension beyond the EE saturation threshold does not increase model prediction accuracies, so a minimal model that best estimates the data statistics can be inferred. Although the saturated EE is smaller than the maximum EE allowed by the area law, our minimal model still achieves ~99% training accuracies in realistic sentiment analysis data sets. Thus, low EE is not a warrant against the adoption of single-layer RACs for NLP. Contrary to a common belief that long-range information propagation is the main source of RNNs' successes, we show that single-layer RACs harness high expressiveness from the subtle interplay between the information propagation and the word vector embeddings. Our work sheds light on the phenomenology of learning in RACs, and more generally on the explainability of RNNs for NLP, using tools from many-body quantum physics.

Sentiment Analysis

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Fock State-enhanced Expressivity of Quantum Machine Learning Models

Conference on Lasers and Electro-Optics (2021)

Beng Yee Gan Daniel Leykam Dimitris G. Angelakis

We propose quantum classifiers based on encoding classical data onto Fock states using tunable beam-splitter meshes, similar to the boson sampling architecture. We show that higher photon numbers enhance the expressive power of the circuit.

Fock state

Beam splitter

Splitter

10.1364/cleo_at.2021.jw1a.73

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Citations (2)

Quantum plasmonics of a metal nanoparticle array for on-chip nanophotonic network

Bulletin of the American Physical Society (2013)

Changhyoup Lee Changsuk Noh Dimitris G. Angelakis Mark Tame James Lim

Nanophotonics

Plasmonic Nanoparticles

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Quantum phase transitions for light and XY spin models in coupled cavity arrays

Bulletin of the American Physical Society (2007)

Dimitris G. Angelakis Marcelo F. Santos Sougato Bose

Classical XY model

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Coherent control of steady state entanglement in driven cavity arrays

arXiv (Cornell University) (2009)

Dimitris G. Angelakis Li Dai L. C. Kwek

We show that coherent control of the steady-state long-distance entanglement between pairs of cavity-atom systems in an array of lossy and driven coupled resonators is possible. The cavities are doped with atoms and are connected through wave guides, other cavities or fibers depending on the implementation. We find that the steady-state entanglement can be coherently controlled through the tuning of the phase difference between the driving fields. It can also be surprisingly high in spite of the pumps being classical fields. For some implementations where the connecting element can be a fiber, long-distance steady state quantum correlations can be established. Furthermore, the maximal of entanglement for any pair is achieved when their corresponding direct coupling is much smaller than their individual couplings to the third party. This effect is reminiscent of the establishment of coherence between otherwise uncoupled atomic levels using classical coherent fields. We suggest a method to measure this entanglement by analyzing the correlations of the emitted photons from the array and also analyze the above results for a range of values of the system parameters, different network geometries and possible implementation technologies.

Coherent control

Lossy compression

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Citations (4)

Photonic band structure design using persistent homology

APL Photonics (2021)

Daniel Leykam Dimitris G. Angelakis

The machine learning technique of persistent homology classifies complex systems or datasets by computing their topological features over a range of characteristic scales. There is growing interest in applying persistent homology to characterize physical systems such as spin models and multiqubit entangled states. Here, we propose persistent homology as a tool for characterizing and optimizing band structures of periodic photonic media. Using the honeycomb photonic lattice Haldane model as an example, we show how persistent homology is able to reliably classify a variety of band structures falling outside the usual paradigms of topological band theory, including “moat band” and multi-valley dispersion relations, and thereby control the properties of quantum emitters embedded in the lattice. The method is promising for the automated design of more complex systems such as photonic crystals and Moiré superlattices.

Persistent Homology

Homology

Lattice (music)

10.1063/5.0041084

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Citations (4)

Repulsively induced photon superbunching in driven resonator arrays

Physical Review A (2013)

Thomas Grujic Stephen R. L. Clark Dieter Jaksch Dimitris G. Angelakis

We analyze the nonequilibrium behavior of driven nonlinear photonic resonator arrays under the selective excitation of specific photonic many-body modes. Targeting the unit-filled ground state, we find a counterintuitive ``superbunching'' in the emitted photon statistics in spite of relatively strong on-site repulsive interaction. We consider resonator arrays with Kerr nonlinearities described by the Bose-Hubbard model, but also show that an analogous effect is observable in near-future experiments coupling resonators to two-level systems as described by the Jaynes-Cummings-Hubbard Hamiltonian. For the experimentally accessible case of a pair of coupled resonators forming a photonic molecule, we provide an analytical explanation for the nature of the effect.

Hamiltonian (control theory)

Bistability

Counterintuitive

10.1103/physreva.87.053846

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Citations (38)