Coherent quantum transport in photonic lattices

Armando Perez-Leija, Robert Keil, Alastair Kay, Hector Moya-Cessa, Stefan Nolte, Leong-Chuan Kwek, Blas M. Rodríguez-Lara, Alexander Szameit, and Demetrios N. Christodoulides

Phys. Rev. A 87, 012309 – Published 14 January 2013

Abstract

Transferring quantum states efficiently between distant nodes of an information processing circuit is of paramount importance for scalable quantum computing. We report on an observation of a perfect state transfer protocol on a lattice, thereby demonstrating the general concept of transporting arbitrary quantum information with high fidelity. Coherent transfer over 19 sites is realized by utilizing judiciously designed optical structures consisting of evanescently coupled waveguide elements. We provide unequivocal evidence that such an approach is applicable in the quantum regime, for both bosons and fermions, as well as in the classical limit. Our results illustrate the potential of the perfect state transfer protocol as a promising route towards integrated quantum computing on a chip.

Received 19 July 2012

DOI:https://doi.org/10.1103/PhysRevA.87.012309

Authors & Affiliations

Armando Perez-Leija^1,*, Robert Keil^2,*, Alastair Kay^3,4,*, Hector Moya-Cessa^1,5, Stefan Nolte², Leong-Chuan Kwek^4,6, Blas M. Rodríguez-Lara⁵, Alexander Szameit², and Demetrios N. Christodoulides^1,†

¹CREOL/College of Optics, University of Central Florida, Orlando, Florida 32816, USA
²Institute of Applied Physics, Friedrich-Schiller Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
³Keble College, Parks Road, University of Oxford, Oxford OX1 3PG, United Kingdom
⁴Centre for Quantum Technologies, National University of Singapore, Singapore 117543
⁵INAOE, Coordinación de Óptica, Luis Enrique Erro No.1, 72840 Toantzintla, Pue., México
⁶Institute of Advanced Studies (IAS) and National Institute of Education, Nanyang Technological University, Singapore 639673

^*These authors contributed equally to this work.
^†demetri@creol.ucf.edu

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Issue

Vol. 87, Iss. 1 — January 2013

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Images

Figure 1
Parallel correspondence between (a) Heisenberg spin chains and (b) waveguide arrays. In (a) spin- $1 / 2$ particles in the state $| ↑ ↓ ... ↓ 〉$ involving nearest-neighbor interactions $J_{n}$ . In (b) an array of optical waveguides with evanescent nearest-neighbor coupling $J_{n}$ . In (a) the vertex spin has been flipped up whereas in the waveguide system (b) it is represented by photons being launched into the first waveguide element.Reuse & Permissions
Figure 2
Experimental setup: Light from a 633 nm laser source is coupled into the waveguide array. The intensity evolution is observed from the top via fluorescence from color centers, whereas the output intensity distribution is directly imaged onto a charged-coupled device (CCD).Reuse & Permissions
Figure 3
Transfer of a single-site excitation. (a)–(d) Experimental fluorescence images of the intensity evolution and near-field images of the output facet after cleaving the device at $z_{f} = 94 mm$ from light injected into the 1st, 2nd, 18th, and 19th waveguide elements, and (e)–(h) the corresponding theoretical dynamics.Reuse & Permissions
Figure 4
Correlation matrices $Γ_{m, n}$ corresponding to lattice systems having an odd (left) or even (right) number of elements. Theoretical comparison between (a), (b) fermionic and (c), (d) bosonic correlations when the two edge sites are excited. (e), (f) Experimentally obtained correlations using classical randomized sources emulating separable single photon states injected at the two edge sites of these arrays. All results are obtained at $z_{f} / 2$ .Reuse & Permissions
Figure 5
Measured coupling-distance dependence used for the state transfer experiment at $633 nm$ . The data points in (a) show the waveguide separations as programed into the fabrication stage, while the points in (b) were obtained by measuring the actual positions with a microscope.Reuse & Permissions
Figure 6
Comparison of experimental data (lower curve) with theoretical predictions for both an ideal system (upper curve) and the one produced (middle curve, utilizing postproduction identification of system parameters) in selected waveguides. In each case, intensity is plotted as a function of the position along the sample, $Z$ , which corresponds to time in a spin chain. Light was injected in waveguide 1. The intensity is normalized, with unity indicating that all the light is contained in the corresponding waveguide. The vertical line depicted on the second column, lowest row symbolizes the optimum transfer distance $z_{f} = 94 mm$ . Note that in every case the middle curve and the upper curve have an offset of 0.1 and 0.2, respectively.Reuse & Permissions

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