Indistinguishability and interference in the coherent control of atomic and molecular processes

Certifying the quantumness of a generalized coherent control scenario

We consider the role of quantum mechanics in a specific coherent control scenario, designing a "coherent control interferometer" as the essential tool that links coherent control to quantum fundamentals. Building upon this allows us to rigorously display the genuinely quantum nature of a generalized weak-field coherent control scenario (utilizing 1 vs. 2 photon excitation) via a Bell-CHSH test. Specifically, we propose an implementation of "quantum delayed-choice" in a bichromatic alkali atom photoionization experiment. The experimenter can choose between two complementary situations, which are characterized by a random photoelectron spin polarization with particle-like behavior on the one hand, and by spin controllability and wave-like nature on the other. Because these two choices are conditioned coherently on states of the driving fields, it becomes physically unknowable, prior to measurement, whether there is control over the spin or not.

Distinguishability and chiral stability in solution: effects of decoherence and intermolecular interactions

We examine the effect of decoherence and intermolecular interactions (chiral discrimination energies) on the chiral stability and the distinguishability of initially pure versus mixed states in an open chiral system. Under a two-level approximation for a system, intermolecular interactions are introduced by a mean-field theory, and interaction between a system and an environment is modeled by a continuous measurement of a population difference between the two chiral states. The resultant equations are explored for various parameters, with emphasis on the combined effects of the initial condition of the system, the chiral discrimination energies, and the decoherence in determining: the distinguishability as measured by a population difference between the initially pure and mixed states, and the decoherence process; the chiral stability as measured by the purity decay; and the stationary state of the system at times long relative to the time scales of the system dynamics and of the environmental effects.

Entanglement in interference-based quantum control: the wave function is not enough

We analyze the way entanglement affects features of interference-based quantum control. We show that quantum interferences vanishes in several cases in the process of extracting probabilities from wave functions. As an example, we discuss the loss of quantum interferences when tracing over number states of the radiation field. We also consider the way in which controllability is reduced when tracing over an entire manifold of states whose cumulative probability we wish to control. Finally, we show that it is impossible to control the relative populations of degenerate states (occurring, e.g., in dissociation and chemical reactions) when the relevant transition amplitude is factorizeable, i.e., when it can be written as a product of a purely classical field-dependent part and a purely materialdependent part. Differences between entanglement and non-factorizability of amplitudes are emphasized.

Generation and control of chains of entangled atom-ion pairs with quantum light

Coherent control using quantum light incident upon molecules in an optical lattice is shown to give rise to a direct way of writing arbitrary sequences of entangled atom-ion pairs. There is no evident limitation on the length of the word (i.e., the number of qbits) that can be formed.