Strong interactions of single atoms and photons in cavity QED

An important development in modern physics is the emerging capability for investigations of dynamical processes for open quantum systems in a regime of strong coupling for which individual quanta play a decisive role. Of particular significance in this context is research in cavity quantum electrodynamics which explores quantum dynamical processes for individual atoms strongly coupled to the electromagnetic field of a resonator. An overview of the research activities in the Quantum Optics Group at Caltech is presented with an emphasis on strong coupling in cavity QED which enables exploration of a new regime of nonlinear optics with single atoms and photons

Near-Field Emission of Lead-Sulfide-Selenide Homojunction Lasers

Measurements of the near-field intensity distributions of three lead-sulfide-selenide diode lasers operating near 4.8 μm have been made as a function of injection current. Localized emission in the near field exhibits peaked structure of full width from 5 to 10 μm for operation above threshold. From the dependence of the emission profiles on injection current estimates of 25 cm ^(-1) and 0.09 cm/A are made for the distributed loss and gain coefficients for one of the lasers. Optical confinement perpendicular to the p-n junction can be explained in terms of the homojunction properties

Efficient Quantum Computation with Probabilistic Quantum Gates

With a combination of the quantum repeater and the cluster state approaches, we show that efficient quantum computation can be constructed even if all the entangling quantum gates only succeed with an arbitrarily small probability p. The required computational overhead scales efficiently both with 1/p and n, where n is the number of qubits in the computation. This approach provides an efficient way to combat noise in a class of quantum computation implementation schemes, where the dominant noise leads to probabilistic signaled errors with an error probability 1-p far beyond any threshold requirement

Comment on "Deterministic Single-Photon Source for Distributed Quantum Networking" by Kuhn, Hennrich, and Rempe

I comment on the experiment to realize an "on-demand," reversible single-photon source by Kuhn, Hennrich, and Rempe [Phys. Rev. Lett. 89, 067901 (2002)].Comment: 2 pages, 1 figur

Teleportation of continuous quantum variables

Quantum teleportation is analyzed for states of dynamical variables with continuous spectra, in contrast to previous work with discrete (spin) variables. The entanglement fidelity of the scheme is computed, including the roles of finite quantum correlation and nonideal detection efficiency. A protocol is presented for teleporting the wave function of a single mode of the electromagnetic field with high fidelity using squeezed-state entanglement and current experimental capability

Reply to ``Comment on ``Some implications of the quantum nature of laser fields for quantum computations'' ''

We point out several superficialities in Itano's comment (quant-ph/0211165).Comment: 2 page

Topological Phenomena in Classical Optical Networks

We propose a scheme to realize a topological insulator with optical-passive elements, and analyze the effects of Kerr-nonlinearities in its topological behavior. In the linear regime, our design gives rise to an optical spectrum with topological features and where the bandwidths and bandgaps are dramatically broadened. The resulting edge modes cover a very wide frequency range. We relate this behavior to the fact that the effective Hamiltonian describing the system's amplitudes is long-range. We also develop a method to analyze the scheme in the presence of a Kerr medium. We assess robustness and stability of the topological features, and predict the presence of chiral squeezed fluctuations at the edges in some parameter regimes.Comment: 18 pages, 9 figure

Interference effects in second-harmonic generation within an optical cavity

An experiment is described that investigates certain interference effects for second-harmonic generation within a resonant cavity. By employing a noncollinear geometry, the phases of two fundamental beams from a frequency-stabilized dye laser can be controlled unrestricted by the boundary conditions imposed in an optical cavity containing a KDP crystal and resonant at the second harmonic. The fundamental beams are either traveling or standing waves and generate either one or two coherent sources of ultraviolet radiation within the cavity. The experiment demonstrates explicitly the dependence of second-harmonic phase on the fundamental phases and the dependence of coupling efficiency on the overlap of the harmonic polarization wave with the cavity-mode function. The measurements agree well with a simple theory