Photon-photon Interactions with single atoms coupled to chip-based microresonators

Barak Dayan

Cavity quantum electrodynamics (cavity QED) enables atom-mediated interactions between single photons by enhancing their electric field in micron-scale optical resonators. Such nonlinear interactions at the single photon level bear great significance in physics in general and in Quantum Information Science in particular. I'll review recent advances made in Caltech's Quantum Optics Group in cavity QED with chip-based microresonators, in particular the demonstration of a dynamic photon-blockade, and discuss how these could help tailoring atom-mediated photon-photon interactions.    

Narrow linewidth diode laser for high fidelity ion-qubit manipulation

Roee Ozeri

Ion-qubit quantum manipulations such as initialization, quantum gates and readout are often performed using laser light. Specifically, for manipulating earth-alkaline ion-qubits on narrow a optical quandrupole transition a narrow linewidth laser is required. Here I will describe a compact narrow linewidth diode laser system with which Sr+ ion-qubits are manipulated with high fidelity.

Room Temperature Hybrid Nano Computer- A New Perspective for applying Quantum Mechanics in Classical "Computing"

Yossi Paltiel

Quantum nano-structures are likely to become primary components of future electronic devices. We are trying to develop a novel nano tool box controlling the coupling to the environment and the quantum states, opening a way for room temperature quantum operating devices. Using ultra-small, high-quality nanocrystals the quantum states remain well defined at high temperatures. These may couple to the semiconductor devices by mono layers of organic molecules that serve as efficient controlled pathways. In this way we aim to develop a generic technology for constructing nano-systems in which many devices are interconnected, operate in unison, without inhibiting their quantum nature.

 The optical route to quantum computing

Terry G. Rudolph

All routes to building a quantum computer face significant challenges. Quantum technologies based on single photons are actively pursued partly because they seem to face no greater challenges than other proposed computation architectures, but also because they are certainly the only feasible proposal for quantum networks and communication. Single photon sources are the major challenge to either application of photonic qubits, and I will discuss recent progress on overcoming this hurdle, focussing on quantum dot sources.

The well-tempered 50 Ohm atom – superconducting qubits and beyond 

Nadav Katz

Superconducting Josephson circuits, appropriately designed and isolated, behave quantum mechanically. The observed high fidelity gates, both for single devices and coupled systems, indicate the scalability of this implementation. A key concept is the coupling impedance of  the devices, which is remarkably low. I will review some recent measurements, including the process tomography of a controlled partial collapse (and un-collapse) of a phase qubit and the coherent coupling of the macroscopic circuit to an atomic sized dipole state - demonstrating a quantum memory in this hybrid system. 

 Radiative cascades in charged and neutral quantum dots

David Gershoni

We measured, for the first time, two photon radiative cascades due to sequential recombination of quantum dot confined electron hole pairs in the presence of an additional spectator charge carrier.  We identified direct, all optical cascades involving spin blockaded intermediate states, and indirect cascades, in which non radiative relaxation precedes the second radiative recombination.I will discuss the potential of semiconductor quantum dots as reliable sources for polarization entangled photon pairs and the possibility to use them for entangling information carrying flying qubits (photons) with anchored matter qubits (charge carriers’ spins).

 Optical implementation of quantum information

Mirko Lobino

Until recently, quantum photonic architecture comprised of large-scale (bulk) optical elements, leading to severe limitations in miniaturization, scalability and stability. We developed the first integrated quantum optical circuitry, demonstrating high-fidelity silica-on-silicon integrated optical realizations of key quantum photonic circuits, including two-photon quantum interference with a visibility of 99.5(4)% and a controlled-NOT gate with an average logical basis fidelity of 96.9(1)% We use these devices to demonstrate multi-photon effects relevant to quantum metrology, quantum Information processing, and quantum measurement. The monolithic nature of these devices means that the correct phase can be stably realized in what would otherwise be an unstable interferometer, greatly simplifying the task of implementing sophisticated photonic quantum circuits. The first integrated quantum metrology experiments are demonstrated by beating the standard quantum limit with two- and four-photon entangled states while demonstrating the first re-configurable integrated quantum circuit capable of adaptively controlling levels of non-classical interference of photons.