To handle a simple system: a trapped single ion

Norbert M. Linke

Zheng Xiao-Juan, Xue-mei Xu, Fangping Ouyang +1 more

A simple and scalable scheme is proposed to generate a n-qubit W state in a trapped-ion system without the Lamb–Dicke limit. The n-qubit W state can be generated by the interaction between the ions and the laser field if the collective mode is initially prepared in the single-phonon state and each ion is in the ground state. The scheme only requires a single laser and avoids laser manipulation of the individual ion. The time required to complete the process decreases with the number of ions. The present scheme is not limited to small values of the LD parameter, which greatly enhances operation speeds.

Daniel Stick, Jonathan D. Stern, Christopher R. Monroe

A full-scale quantum computer would work like the standard desktop computer, in that it would have a place to store data, a place where a program manipulates the data, and interconnections to move the data from one to the other. In the computer you are using now, bits of data - stored as quantity of charge or its absence - are transferred from memory to a processor in the form of levels of voltage. At the processor the computer's program determines which logic operations the bits will be subjected to. Once the logic operations are completed, the bits are converted to amounts of charge and stored in memory again. Similarly, in an ion-trap computer, stored qubits would be called from a storage trap to a logic trap, the kind we've been building so far. The two traps would be connected by a long trap that acts like an interconnect or a data bus. It sounds simple, but such a structure would have to be repeated and connected many dozens of times on the same chip to handle the number of ions we'd need. Therefore, a quantum computer equivalent of very-large-scale integration would be required to handle the control circuitry just to move the ions around. The small-scale quantum algorithms that scientists are running today and plan to run in the near future will almost certainly lead to insights that could make full-scale quantum computing, if not easy, at least more tractable.

Miguel Orszag

Yuren Wang, Li-Bang Wang

We demonstrate a simple electronic detection method for trapped ions in a linear Paul trap. Singly charged calcium ions are confined in a linear Paul trap and are driven by an ac electric field at their secular frequency. The collective motion of the ions causes induced current on the trap electrodes, and the current signal is detected by a tuned circuit. This paper describes the design of the tuned circuit and the performance of this detection method. This method can be applied to various species of ions in different trap geometries. It serves as a simple tool to probe the existing ions in the trap, while in some cases, optical detection is not feasible. This method is particularly suitable for demonstration in teaching laboratories where the ion trap systems and detection circuits can be constructed by undergraduate students.

M. Bagheri Harouni, Mahdi Davoudi Darareh