Huang Xue-Ren

A Single Laser Cooled Trapped 40Ca+ Ion in a Miniature Paul Trap

We have observed the phenomenon of phase transition of a few trapped ions in a miniature Paul trap. Judging from the quantum jump signals, a single laser-cooled trapped Ca+ ion has been realized. The ion temperature is estimated to be 22mK. The result shows that the amplitude of ion micromotion is strongly dependent on the rf voltage.

Strings of Ion Crystals in a Linear Trap for Quantum Information Processing

Strings of laser cooled 40Ca+ crystals have been successfully confined in our home-built linear ion trap, and ready for quantum information processing. We find the cloud-crystal phase transition of the trapped ions to be strongly sensitive to the frequencies of the Doppler cooling lasers and to the trapping voltage. The quantum jump of a single ion has been observed by controlling the quadrupole transition of the ion by a weak laser with ultra-narrow bandwidth.

Frequency Measurement of the Electric Quadrupole Transition in a Single Laser-Cooled (40)Ca(+)

The optical frequency of the 4s(2)S(1/2)-3d(2)D(5/2) transition in a single trapped and laser-cooled Ca-40(+) ion is measured with an optical frequency comb system referenced to a hydrogen maser. A 729-nm laser can be locked to the clock transition about ten hours and the Allan deviation is better than 2 x 10(-14)/1000s.

Control of a Cloud of Laser-Cooled 40Ca+ in a Linear Ion Trap

A cloud of laser-cooled 40Ca+ is successfully trapped and manipulated under well control in our home-built linear ion trap, which is designed and constructed solely for studying quantum information processing. By exploring the variation of the ion cloud with respect to the trap parameters, we have optimized the trapping condition and obtained very good fluorescence spectra. We observe the dynamics of the ion cloud, and estimate the temperature of the ion cloud to be of the order of milli-Kelvin.

Measurement of Secular Motion Frequency in Miniature Paul Trap to Ascertain the Stability Parameters

(40)Ca(+) ions are trapped and laser cooled in a miniature Paul trap. The secular motion was observed by the radio-frequency resonance of the ion cloud and Zeeman profile sidebands of a single ion experimentally. The trap stability parameters.. and.. are determined with an uncertainty under 1% by the secular motion frequency measurement. The trap efficiency is 0.75. A practicable suggestion is given for the benefits of a new trap design.

Implementation of a many-qubit Grover search by cavity QED

We explore the possibility of an N-qubit (N > 3) Grover search in cavity QED, based on a fast operation of an N-qubit controlled phase-flip with atoms in resonance with the cavity mode. We demonstrate both analytically and numerically that our scheme can be achieved efficiently to find a marked state with high fidelity and high success probability. As an example, a ten-qubit Grover search is simulated specifically under the discussion of experimental feasibility and challenge. We argue that our scheme is applicable to the case involving an arbitrary number of qubits. As cavity decay is involved in our quantum trajectory treatment, we can analytically understand the implementation of a Grover search subject to dissipation, which will be very helpful for relevant experiments.

Experimental Improvement of Signal of a Single Laser-Cooled Trapped 40Ca+ Ion

A single 40Ca+ ion is loaded in a miniature Paul trap and the probability of directly loading a single ion is above 50%. The signal-to-noise ratio and the storage time for a single ion have been improved by minimizing the ion micromotion and locking a 397 nm cooling laser to a Fabry–Perot interferometer and optogalvanic signal. From the fluorescence spectrum, the ion temperature is estimated to be about 5 mK.

Simulation and Optimization of Miniature Ring-Endcap Ion Traps

With the decrease in dimension of ion traps employed in optical frequency standards and precision spectroscopy, the sensitivity of trapping behavior to trap geometry is more and more prominent. We present a guide for the design and construction of a miniature trap for a single ion confinement, and propose an optimized combination of r(ring)/r(endcap) approximate to 0.5 and z(0) approximate to r(0) within the range of r(0) = 0.7 +/- 0.2 mm. Compared with the trap used by Huang et al. [Phys. Rev. A 84 (2011) 053841], the design can lead to an increase in trap pseudo-potential of more than 20% and a reduction on potential anharmonicity of more than 90%. The improvements make the trap closer to an ideal hyperboloidal trap to confine a single ion tightly with the benefit of weaker micro-motion. Considering the imperfection of electrodes machining and traps alignment, we also demonstrate the importance of trap symmetry, especially on two endcap electrodes.

Measurement of the secular motion frequency and the space charge density in the linear ion trap

This paper reports that a cloud of laser-cooled 40Ca+ is successfully trapped and manipulated in the home-built linear ion trap constructed for quantum information processing (QIP). The frequency of the secular motion and the space charge density of the ion cloud are measured, which help knowing the characteristic of the trapping potential and are the prerequisite of QIP with the trapped ions.