So-Young Baek

Evanescent and propagating wave characteristics of the photonic quantum ring laser

We present the wave propagation characteristics of photonic quantum ring lasers with clear evidence of the evanescence-propagation crossover behavior. The data obtained from the fiber probe measurements of 15–36 μm disk size lasers show that the Rayleigh’s whispering gallery modes always give rise to the propagation mode, with the crossover ranges of 55–80 μm. The three-dimensional but chiral and broken z-axis symmetry nature of the photonic quantum ring cavity appears to guarantee such a crossover to the propagation in general.

Individual addressing of trapped 171Yb+ ion qubits using a microelectromechanical systems-based beam steering system

The ability to individually manipulate the increasing number of qubits is one of the many challenges towards scalable quantum information processing with trapped ions. Using micro-mirrors fabricated with micro-electromechanical systems technology, we focus laser beams on individual ions in a linear chain and steer the focal point in two dimensions. We demonstrate sequential single qubit gates on multiple 171Yb+ qubits and characterize the gate performance using quantum state tomography. Our system features negligible crosstalk to neighboring ions ( <3×10−4), and switching speed comparable to typical single qubit gate times (<2 μs).

High-Resolution Mode-Spacing Measurement of the Blue-Violet Diode Laser Using Interference of Felds Created with Time Delays Greater than the Coherence Time

Multi-mode cw blue-violet diode-lasers exhibit interference revival when the interferometric path-length-difference is much greater than the self-coherence time. Using the equally-spaced and recurring interference envelopes, high-resolution mode-spacing measurement is possible without using high-resolution spectrometers.

Nonlocal Dispersion Cancellation using Entangled Photons

A pair of optical pulses traveling through two dispersive media will become broadened and, as a result, the degree of coincidence between the optical pulses will be reduced. For a pair of entangled photons, however, nonlocal dispersion cancellation in which the dispersion experienced by one photon cancels the dispersion experienced by the other photon is possible. In this paper, we report an experimental demonstration of nonlocal dispersion cancellation using entangled photons. The degree of two-photon coincidence is shown to increase beyond the limit attainable without entanglement. Our results have important applications in fiber-based quantum communication and quantum metrology.

Preparation and characterization of arbitrary states of four-dimensional qudits based on biphotons

We report an experiment on preparation and characterization of general four-dimensional quantum states using ultrafast-pumped frequency-nondegenerate spontaneous parametric down-conversion. We also discuss two additional experimental schemeswhich offermore complete control of the state purity and entropy.

Error compensation of single-qubit gates in a surface-electrode ion trap using composite pulses

The fidelity of laser-driven quantum logic operations on trapped ion qubits tend to be lower than microwave-driven logic operations due to the difficulty of stabilizing the driving fields at the ion location. Through stabilization of the driving optical fields and use of composite pulse sequences, we demonstrate high fidelity single-qubit gates for the hyperfine qubit of a

Minimum-disturbance measurement without postselection

^{171}\text{Yb}^+

Scalable digital hardware for a trapped ion quantum computer

ion trapped in a microfabricated surface electrode ion trap. Gate error is characterized using a randomized benchmarking protocol, and an average error per randomized Clifford group gate of

Generating Entangled States of Two Ququarts Using Linear Optical Elements

3.6(3)\times10^{-4}

High-resolution mode-spacing measurement of the blue-violet diode laser using interference of fields created with time delays greater than the coherence time

is measured. We also report experimental realization of palindromic pulse sequences that scale efficiently in sequence length.