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Physics

The Entangled Dance of Atom Beams

Rachel J. Berkowitz

Published Feb 23, 2021• 0 citations
Publisher

Abstract

hysically distant quantum particles can share properties and can behave as a single object.For pairs of photons, this entangled behavior allows for data transfer between the two particles, for example.Quantum entanglement can also occur between more massive particles, including two individual atoms.Now, in a controlled experiment, Filippo Borselli of the Vienna University of Technology, Austria, and colleagues create traveling beams of entangled atoms that are reliably produced from a reservoir source using two parallel waveguides [1].The experiment could be a starting point for developing integrated quantum circuits and quantum-information processing devices that use pairs of atoms.

DOI
10.1103/physics.14.s23

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hysically distant quantum particles can share properties and can behave as a single object.For pairs of photons, this entangled behavior allows for data transfer between the two particles, for example.Quantum entanglement can also occur between more massive particles, including two individual atoms.Now, in a controlled experiment, Filippo Borselli of the Vienna University of Technology, Austria, and colleagues create traveling beams of entangled atoms that are reliably produced from a reservoir source using two parallel waveguides [1].The experiment could be a starting point for developing integrated quantum circuits and quantum-information processing devices that use pairs of atoms.
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We describe a deterministic and experimentally feasible protocol for generating entangled pairs of ultracold neutral atoms through controlled dissociation of diatomic Feshbach molecules. The dissociation process naturally produces nonlocal quantum correlations in spin, position-momentum, and path degrees of freedom, enabling the deterministic preparation of Einstein-Podolsky-Rosen pairs of massive particles and multiqubit states through hyperentangled encoding. Having each atom of the pair prepared in a matter waveguide, the scheme can be scaled to hundreds of parallel entanglement sources in an array connected to a matter wave optical network of beam splitters, phase shifters, interferometers, tunnel junctions and local detectors. The protocol builds on established techniques, including programmable optical potentials, high-fidelity single-particle control, single-molecule initialization, controlled molecular dissociation, and quantum gas microscopy with near-perfect detection, making it directly implementable with current technology. The proposed architecture naturally integrates with atomtronics circuits and chip-based matter-wave optics, offering a deterministic entanglement source for quantum nonlocality tests, precision metrology, and scalable neutral-atom quantum processors.
One of the cornerstones of quantum physics is the wave nature of matter. It explains experimentally observed effects like interference and diffraction, occurring when an object moves from one place to another along several indistinguishable ways simultaneously. The wave nature disappears when the individual ways are distinguishable. In this case, the particle nature of the object becomes visible. To determine the particle nature quantitatively, the way of the object has to be measured. Here, large progress has been made recently with new techniques, enabling one to investigate single moving atoms in a controlled manner. Two examples are discussed in the following two sections. The first experiment describes an atom interferometer, where the way of the atom is entangled with its internal state. This allows one to explore the origin of wave-particle duality and perform a quantitative test of this fundamental principle. The second experiment reports on the observation of an atom-photon molecule, a bound state between an atom and a single photon. A fascinating aspect of this system is that it makes possible to monitor the motion of a single neutral atom in real time.