Quantum systems engineering

Abstract:

We review theoretical proposals for implementation of quantum computing and quantum communication with quantum optical methods.

Abstract:

We review and compare several schemes for inducing precisely controlled quantum phases in quantum optical systems, We focus in particular on conditional dynamical phases, i.e. phases obtained via state- and time-dependent interactions between trapped two-level atoms and ions, We describe different possibilities for the kind of interaction to be exploited, including cold controlled collisions, electrostatic forces, and dipole-dipole interactions.

Abstract:

A method to change the interaction strength of a two-component condensate by π/2 pulses is introduced. It is shown that applying a specific series of pulses to the condensate leads to an effective time-averaged Hamiltonian, which is of the form of the original two-component Hamiltonian with an interaction strength depending on parameters of the external field. In addition, it is shown that it is possible to store a spin-squeezed state of a condensate for an arbitrarily long time.

Abstract:

We describe a technique for manipulating quantum information stored in collective states of mesoscopic ensembles. Quantum processing is accomplished by optical excitation into states with strong dipole-dipole interactions. The resulting "dipole blockade" can be used to inhibit transitions into all but singly excited collective states. This can be employed for a controlled generation of collective atomic spin states as well as nonclassical photonic states and for scalable quantum logic gates. An example involving a cold Rydberg gas is analyzed.