Quantum walks and wavepacket dynamics on a lattice with twisted photons.
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Hitherto, photonic implementations of quantum walks have mainly been based on multipath interferometric schemes in real space.Exploiting the latter property, we explored the system band structure in momentum space and the associated spin-orbit topological features by simulating the quantum dynamics of Gaussian wavepackets.Our demonstration introduces a novel versatile photonic platform for quantum simulations.
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Affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli 80126, Italy.
ABSTRACT
The "quantum walk" has emerged recently as a paradigmatic process for the dynamic simulation of complex quantum systems, entanglement production and quantum computation. Hitherto, photonic implementations of quantum walks have mainly been based on multipath interferometric schemes in real space. We report the experimental realization of a discrete quantum walk taking place in the orbital angular momentum space of light, both for a single photon and for two simultaneous photons. In contrast to previous implementations, the whole process develops in a single light beam, with no need of interferometers; it requires optical resources scaling linearly with the number of steps; and it allows flexible control of input and output superposition states. Exploiting the latter property, we explored the system band structure in momentum space and the associated spin-orbit topological features by simulating the quantum dynamics of Gaussian wavepackets. Our demonstration introduces a novel versatile photonic platform for quantum simulations. No MeSH data available. Related in: MedlinePlus |
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Mentions: In our first experiment, the step operator Û is implemented by a sequence of a QWP, a QP, and a HWP. The QPs have q = 1/2, so as to induce OAM shifts of ±1. Because of reflection losses (mainly at the QP, which is not antireflection-coated), each step has a transmission efficiency of 86% (but adding an antireflection coating could easily improve this value to >95%). The n-step walk is then implemented by simply cascading a sequence of QWP-QP-HWP on the single optical axis of the system. In the implemented setup, the linear distance d between adjacent steps is small compared to the Rayleigh range zR of the photons, that is, d/zR ≪ 1 (near-field regime), so as to avoid optical effects that would alter the nature of the simulated process; a detailed discussion is provided in the Supplementary Materials. The layout of the apparatus is shown in Fig. 2. A photon pair is generated by spontaneous parametric down-conversion (SPDC) in the product state /H〉/V〉, where H and V stand for horizontal and vertical linear polarization (see the caption of Fig. 2 for details). To carry out a single-particle QW simulation, we split the two input photons with a polarizing beam splitter (PBS); the H-polarized photon only enters the QW setup after being coupled into a single-mode optical fiber (SMF), which sets m = 0. At the exit of the fiber, the initial polarization of the photon is recovered using a QWP-HWP set (not shown in the figure). The V-polarized photon, reflected at the PBS, is sent directly to a detector and provides a trigger, so as to operate the QW simulation in a heralded single-photon quantum regime. |
View Article: PubMed Central - PubMed
Affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli 80126, Italy.
No MeSH data available.