How to Measure the Quantum State of Collective Atomic Spin Excitation

Abstract

The spin state of an atomic ensemble can be viewed as two bosonic modes, i.e., a quantum signal mode and a $c$-numbered ``local oscillator'' mode when large numbers of spin-1/2 atoms are spin-polarized along a certain axis and collectively manipulated within the vicinity of the axis. We present a concrete procedure which determines the spin-excitation-number distribution, i.e., the diagonal elements of the density matrix in the Dicke basis for the collective spin state. By seeing the collective spin state as a statistical mixture of the inherently-entangled Dicke states, the physical picture of its multi-particle entanglement is made clear.

arXiv comment6 pages, to appear in Phys. Rev. A

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Cited by in corpus (3)

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• Collective multipole-like signatures of entanglement in symmetric N-qubit systems
• Measurement schemes for the spin quadratures on an ensemble of atoms