Quantum walks and wavepacket dynamics on a lattice with twisted photons

Cardano, Filippo; Massa, Francesco; Qassim, Hammam; Karimi, Ebrahim; Slussarenko, Sergei; Paparo, D.; Lisio, C. de; Sciarrino, Fabio; Santamato, Enrico; Boyd, Robert W.; Marrucci, Lorenzo

doi:10.1126/sciadv.1500087

Cited by 183 publications

(182 citation statements)

References 44 publications

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“…Quantum walks, both discrete and continuous, have been realised using cold atoms [17,18], single optically trapped atoms [19], trapped ions [20][21][22], and photons. Optical systems have been used to implement quantum walks using bulk optics [23,24], photonic chips [25][26][27][28], fiber optics [29], and hybrid bulkfiber optic approaches [30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Large scale quantum walks by means of optical fiber cavities

Boutari

Feizpour

Barz

et al. 2016

J. Opt.

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We demonstrate a platform for implementing quantum walks that overcomes many of the barriers associated with photonic implementations. We use coupled fiber-optic cavities to implement time-bin encoded walks in an integrated system. We show that this platform can achieve very low losses combined with high-fidelity operation, enabling an unprecedented large number of steps in a passive system, as required for scenarios with multiple walkers. Furthermore the platform is reconfigurable, enabling variation of the coin, and readily extends to multidimensional lattices. We demonstrate variation of the coin bias experimentally for three different values. INTRODUCTIONQuantum walks are the quantum counterparts to random walks. A quantum walker moves by superpositions of possible paths, resulting in a probability amplitude for being observed at a particular position [1][2][3]. Optical multiport interferometers provide an attractive implementation for quantum walks, since optical fields naturally exhibit coherence between pathways and allow multi-walker scenarios using multiple single photons. However, this approach is susceptible to losses, which limit the achievable scale before being overtaken by noise, and which abrogate many of the advantages implied for applications in quantum information processing [4][5][6][7][8][9][10][11][12]. This challenge motivates the development of low-loss, modular, guided-wave interferometer networks for quantum walks.Quantum walks with multiple interacting walkers have been shown to realize universal quantum computation [13]. For the case of multiple non-interacting walkers, quantum walks are also thought to have quantum computational power, as shown by the boson sampling problem [14]. Quantum walks with a single walker can implement quantum computation, though this requires an exponentially large graph [15,16]. A key feature of quantum walks as information processors is that they do not require time-dependent feedforward control. Quantum walks, both discrete and continuous, have been realised using cold atoms [17,18], single optically trapped atoms [19], trapped ions [20][21][22], and photons. Optical systems have been used to implement quantum walks using bulk optics [23,24], photonic chips [25][26][27][28], fiber optics [29], and hybrid bulkfiber optic approaches [30][31][32].In most experimental implementations, the quantum walk takes place over spatial locations arranged in a lattice. The physical size of the lattice then determines the maximum size of the walk. This limitation can be avoided by use of optical cavities, in which case the number of physical elements required is independent of the size of the walk. This approach was first formulated for frequency-encoded quantum walks [33]. From an experimental perspective, a further key advance was the development of optical cavities that implement time-encoded walks [29,30]. In this case, the walker's location is represented by the time at which a pulse completes a round trip of a cavity [29,30]. In practice, the achievable scale of t...

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Section: Introductionmentioning

confidence: 99%

Large scale quantum walks by means of optical fiber cavities

Boutari

Feizpour

Barz

et al. 2016

J. Opt.

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“…By not only harnessing the polarization or frequency of light but also the transverse spatial degree of freedom, a dramatic improvement in the multiplexing of information can be achieved [3,4]. In quantum physics spatial light modes are successfully utilized as laboratory realizations of high-dimensional quantum states [5,6], which are advantageous for quantum secure communication schemes [7], quantum simulation tasks [8] and foundational investigations [9]. However, to fully take advantage of the potential that spatial light modes offer, technologies to manipulate and measure them are essential.…”

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confidence: 99%

Custom-tailored spatial mode sorting by controlled random scattering

2017

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The need to increase data transfer rates constitutes a key challenge in modern information-driven societies. Taking advantage of the transverse spatial modes of light to encode more information is a promising avenue for both classical and quantum photonics. However, to ease access to the encoded information, it is essential to be able to sort spatial modes into different output channels. Here, we introduce a novel way to customize the sorting of arbitrary spatial light modes. Our method relies on the high degree of control over random scattering processes by preshaping of the phase structure of the incident light. We demonstrate experimentally that various sets of modes, irrespective of their specific modal structure, can be transformed to any output channel arrangement. Thus, our method enables full access to all of the information encoded in the transverse structure of the field, for example, azimuthal and radial modes. We also demonstrate that coherence is retained in this complex mode transformation, which opens up applications in quantum and classical information science.Transverse spatial light modes have attracted a much attention because of their special properties and the subsequent broad range of applications [1, 2]. One particularly promising approach uses spatial modes of light to increase data rates in optical communication schemes. By not only harnessing the polarization or frequency of light but also the transverse spatial degree of freedom, a dramatic improvement in the multiplexing of information can be achieved [3,4]. In quantum physics spatial light modes are successfully utilized as laboratory realizations of high-dimensional quantum states [5,6], which are advantageous for quantum secure communication schemes [7], quantum simulation tasks [8] and foundational investigations [9]. However, to fully take advantage of the potential that spatial light modes offer, technologies to manipulate and measure them are essential. Although mature technologies to generate complex spatial modes are available today [10], complex transformations of such modes are still rare and challenging to implement [11][12][13]. The transformation from a given spatial mode to a specific position in a transverse plane, that is, mode sorting or demultiplexing, is an especially interesting transformation in quantum [7,14,15] and classical information schemes [4,16]. A specific example, namely a sorter for modes that differ by their azimuthal structure, has recently been established [17,18] and successfully implemented [4,7,14,15].Here we show that sorting of this type can be implemented through the control of strong scattering processes, a topic that has recently attracted much attention [19]. Such control can allow one to realize complex modulation tasks that have thus far been impossible. Earlier experiments presage the enormous potential that the control over random scattering processes can offer, by e.g. showing enhanced transmission and focusing through opaque, scattering media in the spatial [20][21][22] and temporal d...

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“…In the last few years, the number of experimental validations of the quantum walk paradigm, and investigations towards its use for the coherent manipulation of information at the quantum mechanical level have flourished [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. This therefore paves the way to the full exploitation of the possibilities offered by quantum walks for quantum state engineering in Hilbert spaces of large dimensions, which is in general a difficult task to pursue experimentally.…”

Section: Introductionmentioning

confidence: 99%

Robust quantum state engineering through coherent localization in biased-coin quantum walks

Majury

Boutari

O’Sullivan

et al. 2018

EPJ Quantum Technol.

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We address the performance of a coin-biased quantum walk as a generator for non-classical position states of the walker. We exploit a phenomenon of coherent localization in the position space -resulting from the choice of small values of the coin parameter and assisted by post-selection -to engineer large-size coherent superpositions of position states of the walker. The protocol that we design appears to be remarkably robust against both the actual value taken by the coin parameter and strong dephasing-like noise acting on the spatial degree of freedom. We finally illustrate a possible linear-optics implementation of our proposal, suitable for both bulk and integrated-optics platforms.Quantum walks, which generalize the well-known concept of random walks to the quantum domain, have recently attracted considerable attention in light of the possibility that they offer the capability to explore non-trivial phenomena in statistical mechanics [1], such as interference [2], localization [3-6] and tunnelling, and are able to establish entanglement among either the different degrees of freedom of a walker, or the parties of a multi-walker setting [7][8][9][10][11][12][13]. Quantum walk-based architectures for quantum computation have been proposed and theoretically explored [14], while the possibility to implement quantum simulation through schemes based on the dynamics of a quantum walker are currently being pursued both theoretically and experimentally.In the last few years, the number of experimental validations of the quantum walk paradigm, and investigations towards its use for the coherent manipulation of information at the quantum mechanical level have flourished [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. This therefore paves the way to the full exploitation of the possibilities offered by quantum walks for quantum state engineering in Hilbert spaces of large dimensions, which is in general a difficult task to pursue experimentally.In this paper, we explore exactly such a possibility and exploit the statistical features of a discrete-time quantum walk to engineer non-classical states of an N -dimensional system. Specifically, we make use of special coherent localization effects induced on the position state of a quantum walker by choosing properly the operation describing the tossing of a coin. We demonstrate that high-quality coherent superpositions of fully position states © The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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Quantum walks and wavepacket dynamics on a lattice with twisted photons

Abstract: A discrete quantum walk occurs in the orbital angular momentum space of light, both for a single photon and for two simultaneous photons.

Cited by 183 publications

References 44 publications

Large scale quantum walks by means of optical fiber cavities

Large scale quantum walks by means of optical fiber cavities

Custom-tailored spatial mode sorting by controlled random scattering

Robust quantum state engineering through coherent localization in biased-coin quantum walks

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