Non-local quantum gates: a cavity-quantum-electrodynamics implementation

The problems related to the management of large quantum registers could be handled in the context of distributed quantum computation: unitary non-local transformations among spatially separated local processors are realized performing local unitary transformations and exchanging classical communication. In this paper, a scheme is proposed for the implementation of universal non-local quantum gates such as a controlled NOT (CNOT) and a controlled quantum phase gate (CQPG). The system chosen for their physical implementation is a cavity-quantum-electrodynamics (CQED) system formed by two spatially separated microwave cavities and two trapped Rydberg atoms. The procedures to follow for the realization of each step necessary to perform a specific non-local operation are described.

Calcium signaling in ocular arterioles

Local control of blood flow to the photoreceptors and associated neurons in the retina is largely achieved through changes in tone within the choroidal and retinal arterioles. This is primarily achieved through changes in [Ca2+] within the smooth muscle of these vessels, which regulates cell contraction and vascular constriction. Here we review some aspects of the cell physiology involved in these Ca2+-signaling processes, with particular emphasis on the molecular mechanisms involved. Ca2+-influx across the plasma membrane can occur via a variety of Ca2+-channels, including voltage-operated, store-operated, and receptor-operated channels. Ca2+ may also be released from intracellular stores via RyR-, or IP3R-gated channels in the SR membrane. Using high-speed confocal Ca2+-imaging, we have also demonstrated that the resulting signals are far from homogeneous, with spontaneous activity in retinal arterioles being characterized by both localized Ca2+-sparks and more global Ca2+-waves and oscillations. These signals may be specifically and differentially targeted, for example, to Ca2+-sensitive ion channels (stimulus-excitation coupling), or pathways regulating contraction (stimulus-contraction coupling). Exploring the role of changes in such targeting in disease states will provide exciting opportunities for future research.