Highly efficient, nearly deterministic, and isotope selective generation of Yb + ions by 1-and 2-color photoionization is demonstrated. State preparation and state selective detection of hyperfine states in 171 Yb + is investigated in order to optimize the purity of the prepared state and to timeoptimize the detection process. Linear laser cooled Yb + ion crystals ions confined in a Paul trap are demonstrated. Advantageous features of different previous ion trap experiments are combined while at the same time the number of possible error sources is reduced by using a comparatively simple experimental apparatus. This opens a new path towards quantum state manipulation of individual trapped ions, and in particular, to scalable quantum computing.When investigating fundamental questions related to quantum mechanics experiments are called for where individual quantum systems can be accessed and deterministically manipulated. The interaction of trapped atomic ions among themselves and with their environment can be controlled to a high degree of accuracy, and thus allows for the preparation of well defined quantum states of the ions' internal and motional degrees of freedom. Trapped ions have proven to be well suited for a multitude of investigations, for instance, into entanglement, decoherence, and quantum information processing, and for applications such as atomic frequency standards. Quantum information processing, in particular, requires accurate and precise control of internal and often also of motional quantum dynamics of a collection of trapped ions. In order to eliminate sources of possible errors, and thus prepare the ground to attain the ambitious goal of using trapped ions for large scale quantum computing or quantum simulations, it is desirable to simplify the apparatus used for such experiments as far as possible.An unprecedented degree of control of quantum systems has been reached in recent experiments with trapped ions, for instance, with BeMainly the type of ion used in such experiments determines the experimental infrastructure needed for controlled manipulation of these ions. The available ionic transitions, for instance, determine the radiation sources to be used: In Ca + an optical electric quadrupole transition has been used as a qubit leading to a coherence time limited ultimately by spontaneous radiative decay. More importantly, phase fluctuations of the laser light driving the qubit transition limit the available coherence time, even when using a highly sophisticated light source [4]. Phase fluctuations of the radiation driving the qubit transition do not present a major obstacle, if a hyperfine transition is used as a qubit (as, for instance, in Be + or Cd + ), since such a transition is usually excited by a stimulated two-photon Raman process where only relative fluctuations between the two driving fields limit the available coherence time. Choosing magnetic field insensitive states as a qubit, as was demonstrated recently with Be + , may further contribute to achieving the desired long coh...

The evolution of a quantum system is supposed to be impeded by measurement of an involved observable. This effect has been proven indistinguishable from the effect of dephasing the system's wave function, except in an individual quantum system. The coherent dynamics, on an optical E2 line, of a single trapped ion driven by light of negligible phase drift has been alternated with interrogations of the internal ion state. Retardation of the ion's nutation, equivalent to the quantum Zeno effect, is demonstrated in the statistics of sequences of probe-light scattering "on" and "off" detections, the latter representing back-action-free measurement.The act of measuring an observable of a system that obeys quantum mechanics consists of recording one of the eigenvalues and rejecting all the other ones. This act is accompanied by sudden transition of the system's wave function into the eigenfunction corresponding to the recorded eigenvalue; the response of the system is known as the "state reduction" [1]. It has been recognized that repeated measurements retard, or even impede, the evolution of a quantum system to the extent that they may inhibit the evolution [2,3]. This consequence, the "quantum Zeno effect" [4] alluding to eleatic ontology, has aroused a great wealth of work devoted to contemplating the subject [5], and an attempt to observe it: An experiment including the drive and probe laser irradiation of an ensemble of some 5000 beryllium ions confined in an ion trap has resulted in complete agreement with quantum-mechanical predictions [6]. However, these predictions based on the deletion, in the acts of measurement, of all superpositions of eigenstates can be identified with the effect of any phase perturbations by the environment upon the multi-particle wave function of the system ("dephasing"). In fact, a perturbation via the back action of the meter on the quantum system has been invoked as the origin of QZE [7][8][9][10]. The ambiguity of the initial t 2 evolution being set back by the measurements [2,3,11], or dephasing, − i.e. effect of measurement vs dynamical effect − is unresolvable since a decision would require knowledge of the states of all the members (the "micro-state") of any ensemble that remain unknown in a global measurement. Here, both the result of a particular measurement, and the temporal evolution of the ensemble's state, do not statistically depend on the results of previous measurements; they are deterministic, save the "projection noise" [12,13] that affects measurements of non-commuting observables and vanishes with a large enough ensemble. However, with an individual system, the result of a measurement as well as the system's evolution do statistically depend on the history, and the results are in general found indeterministic, except after particular preparation of the system, in an eigenstate of the observable to be detected [13]. The statistics of the results will embody the signature of the state reductions by the measurements, and their effect cannot be ascribed to dephasing [14...

Neutral ytterbium (YbI) and singly ionized ytterbium (YbII) is widely used in experiments in quantum optics, metrology and quantum information science. We report on the investigation of isotope selective two-photon-ionization of YbI that allows for efficient loading of ion traps with YbII. Results are presented on two-colour (399 nm and 369 nm) and single-colour (399 nm) photoionization and their efficiency is compared to electron impact ionization. Nearly deterministic loading of a desired number of YbII ions into a linear Paul trap is demonstrated.

The driven evolution of the spin of an individual atomic ion on the ground-state hyperfine resonance is impeded by the observation of the ion in one of the pertaining eigenstates. Detection of resonantly scattered light identifies the ion in its upper "bright" state. The lower "dark" ion state is free of relaxation and correlated with the detector by a null signal. Null events represent the straightforward demonstration of the quantum Zeno paradox. Also, high probability of survival was demonstrated when the ion, driven by a fractionated π pulse, was probed and monitored during the intermissions of the drive, such that the ion's evolution is completely documented.