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  • Featured in Physics
  • Open Access

Quantum Spin Lenses in Atomic Arrays

A. W. Glaetzle1,2,3,4, K. Ender1,2, D. S. Wild5, S. Choi5, H. Pichler6,5, M. D. Lukin5, and P. Zoller1,2,7

  • 1Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria
  • 2Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck, Austria
  • 3Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
  • 4Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
  • 5Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
  • 6ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA
  • 7Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany

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Phys. Rev. X 7, 031049 – Published 20 September, 2017

DOI: https://doi.org/10.1103/PhysRevX.7.031049

Abstract

We propose and discuss quantum spin lenses, where quantum states of delocalized spin excitations in an atomic medium are focused in space in a coherent quantum process down to (essentially) single atoms. These can be employed to create controlled interactions in a quantum light-matter interface, where photonic qubits stored in an atomic ensemble are mapped to a quantum register represented by single atoms. We propose Hamiltonians for quantum spin lenses as inhomogeneous spin models on lattices, which can be realized with Rydberg atoms in 1D, 2D, and 3D, and with strings of trapped ions. We discuss both linear and nonlinear quantum spin lenses: in a nonlinear lens, repulsive spin-spin interactions lead to focusing dynamics conditional to the number of spin excitations. This allows the mapping of quantum superpositions of delocalized spin excitations to superpositions of spatial spin patterns, which can be addressed by light fields and manipulated. Finally, we propose multifocal quantum spin lenses as a way to generate and distribute entanglement between distant atoms in an atomic lattice array.

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Synopsis

A Lens to Focus Spins

Published 20 September, 2017

A quantum bit stored in the spin excitation of an atomic cloud could be “focused” onto the quantum state of a single atom.

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Popular Summary

A formidable challenge in quantum computing is how to interface photons, which transmit information, with stationary qubits, used for storage and manipulation. To convert a photon into a stationary qubit, the photon may be sent into a cloud of atoms, where it is absorbed. This triggers a collective behavior among the atomic spins (known as a spin excitation) that is spread out over many atoms and cannot be manipulated easily. If the spin excitation could be “focused” onto a single atom, the spin (which acts as a qubit) could then be operated on using the well-developed tools of atomic quantum computing. We introduce the concept of a “quantum spin lens” that does just that. It not only focuses the spin excitation of an atomic cloud but also extracts information stored in one atom and sends it elsewhere in the form of photons.

Our description of the spin lens is guided by a close analogy with optical lenses, which focus light and form the essential building blocks of complex imaging systems. We show how the spin lens can be implemented in lattices of atoms by modifying the coupling between atoms with laser light. We study the focusing dynamics of one or more excitations, and even of quantum superpositions of different types of excitations, taking into account interactions between the excitations. By mapping different excitations into different spatial regions, it is possible to address and manipulate them separately, which could be exploited to create highly entangled states of light.

Viewed from a different perspective, quantum spin lenses can be used in coherent quantum spintronics to design and exploit coherent spin transport to achieve spatial focusing of delocalized spin excitations.

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Phys. Rev. X 7, 031049– Published 20 September, 2017
  • Received 28 April 2017
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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