Matthew Joseph Paul Petrasiunas

Wavelength-scale imaging of trapped ions using a phase Fresnel lens

A microfabricated phase Fresnel lens was used to image ytterbium ions trapped in a radio frequency Paul trap. The ions were laser cooled close to the Doppler limit on the 369.5 nm transition, reducing the ion motion so that each ion formed a near point source. By detecting the ion fluorescence on the same transition, near-diffraction-limited imaging with spot sizes of below 440 nm (FWHM) was achieved. To our knowledge, this is the first demonstration of wavelength-scale imaging of trapped ions and the highest imaging resolution ever achieved with atoms in free space.

Picosecond 554 nm yellow-green fiber laser source with average power over 1 W

We demonstrate a source of 554 nm pulses with 2.7 ps pulse duration and 1.41 W average power, at a repetition rate of 300 MHz. The yellow-green pulse train is generated from the second harmonic of a 1.11 μm fiber laser source in periodically-poled stoichiometric LiTaO3. A total fundamental power of 2.52 W was used, giving a conversion efficiency of 56%.

Millikelvin spatial thermometry of trapped ions

We demonstrate millikelvin thermometry of laser-cooled trapped ions with high-resolution imaging. This equilibrium approach is independent of the cooling dynamics and has lower systematic error than Doppler thermometry, with ±5mK accuracy and ±1mK precision. We used it to observe the highly anisotropic dynamics of a single ion,finding temperatures of 15K simultaneously along different directions. This thermometry technique can offer new insights into quantum systems sympathetically cooled by ions, including atoms, molecules, nanomechanical oscillators and electric circuits. Laser-cooled trapped ions are a nearly ideal system for investigation of quantum physics. The internal ion states are strongly decoupled from the surrounding environment and can exhibit coherence times of many seconds. In ultrahigh vacuum the motions of the ions are strongly coupled together, but otherwise exhibit good immunity to external perturbations. Precision manipulation of ions at the quantum level is readily achieved through the use of lasers and electromagnetic fields. These properties have made laser-cooled trapped ions a preferred platform for implementing experiments in quantum information processing (QIP) (1-4) and precision metrology (5, 6). The strong Coulomb coupling makes laser-cooled trapped ions attractive for sympathetic cooling at millikelvin temperatures in investigations of fundamental physics (7), dynamics of complex molecular (8, 9) and biomolecular (10) ions, nano-mechanical oscillators (11, 12), resonant electric circuits (13) and Bose-Einstein condensates (14). Millikelvin thermometry is a key diagnostic in all these experiments. Cooling near the Doppler limit, 1mK, is a precondition for studies of quantum dynamics and precision measurements. Millikelvin thermometry is crucial for quantifying the effectiveness of Doppler

Ultrafast, high repetition rate, ultraviolet, fiber-laser-based source: application towards Yb + fast quantum-logic

Trapped ions are one of the most promising approaches for the realization of a universal quantum computer. Faster quantum logic gates could dramatically improve the performance of trapped-ion quantum computers, and require the development of suitable high repetition rate pulsed lasers. Here we report on a robust frequency upconverted fiber laser based source, able to deliver 2.5 ps ultraviolet (UV) pulses at a stabilized repetition rate of 300.00000 MHz with an average power of 190 mW. The laser wavelength is resonant with the strong transition in Ytterbium (Yb+) at 369.53 nm and its repetition rate can be scaled up using high harmonic mode locking. We show that our source can produce arbitrary pulse patterns using a programmable pulse pattern generator and fast modulating components. Finally, simulations demonstrate that our laser is capable of performing resonant, temperature-insensitive, two-qubit quantum logic gates on trapped Yb+ ions faster than the trap period and with fidelity above 99%.

Picosecond, ultraviolet fiber laser at 300MHz repetition rate: Resonant quantum logic gate source

We engineered a fiber laser source capable to produce 2.5ps UV pulses at 300MHz repetition rate. Laser wavelength resonates with one of the strong transition in Yb+ ion, and it will enable us to coherently manipulate Yb+ via π-transitions to make fast entangling gates.

Three-photon excitation of quantum dots with a telecom-band ultrafast fiber laser

AbstractWe demonstrate three-photon excitation in quantum dots with a mode-locked fiber laser operating in the telecommunications band. We compare spectra and intensity dependence of fluorescence from one- and three-photon excitation of commercially available 640-nm quantum dots, using a 372-nm diode laser for one-photon excitation and 116-fs pulses from a mode-locked fiber laser with a center wavelength of 1,575 nm for three-photon excitation.

Ultrafast excitation of quantum dots with a fibre laser for deep tissue imaging

Fluorescence from three photon absorption was observed in CdSe quantum dots excited with ultrashort pulses from a telecom band Erbium fibre laser. Reduced scattering at longer wavelengths makes this approach interesting for deep tissue imaging.

High-power ultrafast laser source with 300 MHz repetition rate for trapped-ion quantum logic

We implement a mode-locked UV laser source at 300 MHz repetition rate for use in fast quantum logic gates with trapped ions. The architecture allows scaling of repetition rate into the GHz range.

Imaging the temperature of trapped ions

Thermometry of trapped ions is an important diagnostic for quantum computing and atomic clocks. Existing thermometry techniques for trapped ions rely on spectroscopy, which is vulnerable to systematic errors induced by laser cooling dynamics. High resolution imaging of ion fluorescence provides a steady state thermometry technique which is independent of the laser cooling dynamics. To achieve sufficient resolution requires a high numerical aperture imaging system with low aberration.