Ion trap quantum computing

On Thursday I attended a seminar by Simon Webster from the Ion trap QC group in Oxford. I didn’t realise that ion trap QC was so advanced. Having spent so much time in the happy world of LSI Josephson logic, I had a prehistoric picture of an ion trap being a large metallic cavity surrounded by huge electrodes similar to plasma confinement systems. But no, it can be done to micrometer precision on chip with ions trapped in tiny channels. You can shuttle individual ions, or little chains of them around the chip, allow them to interact and evolve to perform the computation, and then move them elsewhere, or read them out.

Photo © Oxford Ion trap group

Alas, it is still only possible to manipulate a couple of qubits at the moment, as is the case with most QC realizations. The qubits themselves are formed by manipulating transitions between energy levels of the ions. In this case, Ca+ ions. Entanglement can occur for example between the ion and the photon emitted during a relaxation from an excited state. Therefore one advantage of Ion trap QC is that it is natively good at handling static (ionic) and flying (photonic) qubits with the same technology, and quantum information can therefore be transferred over long distances and on/off chip quite easily.

Exciting stuff. I’ve still got my money on Josephson junctions, but competition in experimental QC is healthy 🙂


Overview of the Oxford Ion trap
Nature paper on Ion trap QC
Info from MIT
PhysOrg report


4 thoughts on “Ion trap quantum computing

  1. Geordie says:

    Do any of these groups use superconducting circuits for these types of traps?

  2. physicsandcake says:

    The ones I’ve seen have all been GaAs – I’m not sure you’d be able to get the trap field profile with superconducting electrodes.

    I guess it’s also easier to get the lasers in for the Doppler cooling of the ions with room temperature apparatus (although optical access to fridge stages is not unheard of).

  3. Chip says:

    Microfabricated ion traps often have metal electrodes on a dielectric substrate. A superconducting ion trap has already been demonstrated (; There are several working ion traps in cryostats.

  4. Chip says:

    Note: the trap pictured above has gold electrodes on a quartz substrate.

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