ABSTRACT:
Quantum mechanics allows for many-particle wave functions that cannot
be factorized into a product of single-particle wave functions, even when
the constituent particles are entirely distinct. Such entangled states
explicitly demonstrate the nonlocal character of quantum theory,
have been suggested for use in high-precision spectroscopy,
and are a fundamental element of schemes for quantum communication,
cryptography, and computation. In general, the more particles which can be
entangled, the more clearly nonclassical effects are exhibited
and the more useful the states are for quantum applications. In pursuit of
these goals, we have demonstrated a recently proposed entanglement technique
applicable to trapped ions. Coupling between the ions is provided by
the Coulomb interaction through their collective motional degrees of
freedom, but actual motional excitation is minimized. Entanglement is achieved
using a single laser pulse, and the method can in principle be applied to
any number of ions. We used this technique to generate entangled states of
two, and for the first time, four particles. |