J. P. Home

Complete Methods Set for Scalable Ion Trap Quantum Information Processing

Hi Fi Quantum Computing In quantum information processing, one goal is to control the entangled states of objects such that they can interact during logical operations but otherwise have minimal interactions with their environment. In one scheme for quantum computing, ions are trapped within and physically moved by electric fields. One drawback is that the entangled states can be sensitive to stray magnetic fields. Home et al. (p. 1227, published online 6 August 2009) show that coupling of the ions (in this case, 9Be+) with a second ion (24Mg+) can create states that are relatively insensitive to magnetic fields and also allows for recooling of the ions during operation. This approach can minimize the loss of fidelity that occurs during ion transport. Coupling of different ions creates states that are insensitive to stray magnetic fields and more robust for quantum computing. Large-scale quantum information processors must be able to transport and maintain quantum information and repeatedly perform logical operations. Here, we show a combination of all of the fundamental elements required to perform scalable quantum computing through the use of qubits stored in the internal states of trapped atomic ions. We quantified the repeatability of a multiple-qubit operation and observed no loss of performance despite qubit transport over macroscopic distances. Key to these results is the use of different pairs of 9Be+ hyperfine states for robust qubit storage, readout, and gates, and simultaneous trapping of 24Mg+ “re-cooling” ions along with the qubit ions.

Isotope-selective photoionization for calcium ion trapping

We present studies of resonance-enhanced photoionization for isotope-selective loading of

Entangled mechanical oscillators

{\mathrm{Ca}}^{+}

Coherent diabatic ion transport and separation in a multizone trap array.

into a Paul trap. The

Realization of a programmable two-qubit quantum processor

{4s}^{2}{}^{1}{S}_{0}\ensuremath{\leftrightarrow}4s4p{}^{1}{P}_{1}

Simplified motional heating rate measurements of trapped ions

transition of neutral calcium is driven by a 423 nm laser and the atoms are photoionized by a second laser at 389 nm. Isotope selectivity is achieved by using crossed atomic and laser beams to reduce the Doppler width significantly below the isotope shifts in the 423 nm transition. The loading rate of ions into the trap is studied under a range of experimental parameters for the abundant isotope

Fluorescence during Doppler cooling of a single trapped atom

{}^{40}{\mathrm{Ca}}^{+}.

Deterministic entanglement and tomography of ion–spin qubits

Using the fluorescence of the atomic beam at 423 nm as a measure of the Ca number density, we estimate a lower limit for the absolute photoionization cross section of 170(60) Mb. We achieve loading and laser cooling of all the naturally occurring isotopes, without the need for enriched sources. Laser heating/cooling is observed to enhance the isotope selectivity. In the case of the rare species

Long-lived mesoscopic entanglement outside the Lamb-Dicke regime.

{}^{43}{\mathrm{Ca}}^{+}

Randomized benchmarking of multiqubit gates.

and