Quantum Effects in Charged Particle Traps

Abstract

It is a fundamental feature of quantum mechanics that a group of particles can be in a state described by one common wavefunction which cannot be factored into individual particle wavefunctions; they are then said to be in an entangled state [294-296]. A measurement of the state of a constituent part of the entangled system determines the state of all the others. In a system that is not entangled, the states of the individual particles are determined independently. Ions isolated and trapped in vacuo in electromagnetic fields provide an unparalleled means of realizing long-lived entangled quantum states [297] through the coupling of the normal modes of oscillation in the trap by the long range Coulomb interaction [298-300]. The realization of entangled states among many ions [301,302] has enabled quantum applications ranging from precision metrology [255, 303] to quantum information processing [304, 305]. The main obstacle to maintaining entanglement and implementing these applications is the loss of coherence due to interactions with the environment. Among the important causes of decoherence are spontaneous emission [306-308], fluctuations in the applied trapping and cooling fields, and collisions with the residual background gas particles. Great progress has been achieved in recent years to overcome these difficulties and demonstrate quantum entanglement phenomena in trapped ions.