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Deterministic generation of multiparticle entanglement by quantum Zeno dynamics

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Science  18 Sep 2015:
Vol. 349, Issue 6254, pp. 1317-1321
DOI: 10.1126/science.aaa0754

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Entangling atoms by persistent poking

In quantum mechanics, repeated measurements targeting a particular unoccupied state of the system can keep that state from being occupied. Barontini et al. used this so-called quantum Zeno effect to restrict the dynamics of an ensemble of 36 87Rb atoms acting as qubits and residing in an optical cavity. The measurement of the cavity transmission blocked off the collective state in which all qubits were in their ground state. The ensuing dynamics resulted in the entanglement of the atoms, creating a potential resource for quantum information processing.

Science, this issue p. 1317

Abstract

Multiparticle entangled quantum states, a key resource in quantum-enhanced metrology and computing, are usually generated by coherent operations exclusively. However, unusual forms of quantum dynamics can be obtained when environment coupling is used as part of the state generation. In this work, we used quantum Zeno dynamics (QZD), based on nondestructive measurement with an optical microcavity, to deterministically generate different multiparticle entangled states in an ensemble of 36 qubit atoms in less than 5 microseconds. We characterized the resulting states by performing quantum tomography, yielding a time-resolved account of the entanglement generation. In addition, we studied the dependence of quantum states on measurement strength and quantified the depth of entanglement. Our results show that QZD is a versatile tool for fast and deterministic entanglement generation in quantum engineering applications.

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