Atomic Physics Seminars

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.