arXiv subjects

Dimitris G. Angelakis

Publications and source records attributed to Dimitris G. Angelakis.

80 records · Page 5Linked to original sources

arXiv2008

Many body effects and cluster state quantum computation in strongly interacting systems of photons

We discuss the basic properties of a recently proposed hybrid light-matter system of strongly interacting photons in an array of coupled cavities each doped with a single two level system. Using the non-linearity generated from the photon blockade effect, we predict strong correlations between the hopping photons in the array, and show the possibility of observing a phase transition from a polaritonic insulator to a superfluid of photons. In the Mott phase, this interaction can be mapped to an array of spins. We show how the remaining Hamiltonian, in conjunction with individual spin manipulation, can thus be used for simulating spin chains (useful for state transfer protocols) and cluster state quantum computation.

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arXiv2007

Implementing universal quantum gates in coupled cavities

We study a linear array of coupled cavities interacting with two level systems and show how to construct individually addressable qubits in this system from the long-lived atom-photon excitations (polaritons) at each site. We derive the system dynamics and show that is described by an XY Hamiltonian. We proceed by showing how to implement non-local quantum gates and show that combined with the inherent ability for individual addressing, universal quantum computation is possible in this system. We finally discuss the prospects for experimental implementation using various technologies involving dopants as atoms, quantum dots or Cooper pair boxes.

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arXiv2007

Cluster state quantum computation in coupled cavity arrays

Measurement-based quantum computation has revolutionized quantum information processing, and the physical systems with which it can be implemented. One simply needs the ability to prepare a particular state, known as the cluster state, and subsequently to perform single-qubit measurements on it. Nevertheless, a scalable implementation is yet to be realized. Here we propose a hybrid light-matter system comprised of coupled cavities interacting with two level systems. Utilising the stable, individually addressable, qubits resulting from the localised long-lived atom-photon excitations, we demonstrate how to use the natural system dynamics to `weave' these qubits into a cluster state and propose the implementation of quantum algorithms employing just two rows of qubits. Finally, we briefly discuss the prospects for experimental implementation using atoms, quantum dots or Cooper pair boxes.

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arXiv2007

Photon blockade induced Mott transitions and XY spin models in coupled cavity arrays

As photons do not interact with each other, it is interesting to ask whether photonic systems can be modified to exhibit the phases characteristic of strongly coupled many-body systems. We demonstrate how a Mott insulator type of phase of excitations can arise in an array of coupled electromagnetic cavities, each of which is coupled resonantly to a {\em single} two level system (atom/quantum dot/Cooper pair) and can be individually addressed from outside. In the Mott phase each atom-cavity system has the same integral number of net polaritonic (atomic plus photonic) 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. We also show that for zero detuning, the system can simulate the dynamics of many body spin systems.

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arXiv2007

A proposal for the implementation of quantum gates with photonic-crystal coupled cavity waveguides

Quantum computers require technologies that offer both sufficient control over coherent quantum phenomena and minimal spurious interactions with the environment. We show, that photons confined to photonic crystals, and in particular to highly efficient waveguides formed from linear chains of defects doped with atoms can generate strong non-linear interactions which allow to implement both single and two qubit quantum gates. The simplicity of the gate switching mechanism, the experimental feasibility of fabricating two dimensional photonic crystal structures and integrability of this device with optoelectronics offers new interesting possibilities for optical quantum information processing networks.

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arXiv2007

Transfer of a Polaritonic Qubit through a Coupled Cavity Array

We demonstrate a scheme for quantum communication between the ends of an array of coupled cavities. Each cavity is doped with a single two level system (atoms or quantum dots) and the detuning of the atomic level spacing and photonic frequency is appropriately tuned to achieve photon blockade in the array. We show that in such a regime, the array can simulate a dual rail quantum state transfer protocol where the arrival of quantum information at the receiving cavity is heralded through a fluorescence measurement. Communication is also possible between any pair of cavities of a network of connected cavities.

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arXiv2004

Photonic crystals and inhibition of spontaneous emission: an introduction

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.

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arXiv2001

Verifying Atom Entanglement Schemes by Testing Bell's Inequality

Recent experiments to test Bell's inequality using entangled photons and ions aimed at tests of basic quantum mechanical principles. Interesting results have been obtained and many loopholes could be closed. In this paper we want to point out that tests of Bell's inequality also play an important role in verifying atom entanglement schemes. We describe as an example a scheme to prepare arbitrary entangled states of N two-level atoms using a leaky optical cavity and a scheme to entangle atoms inside a photonic crystal. During the state preparation no photons are emitted and observing a violation of Bell's inequality is the only way to test whether a scheme works with a high precision or not.

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