Trapped-ion quantum logic with near-field microwave-driven gates
David Allcock, National Institute of Standards and Technology, Boulder
Hyperfine qubits in laser-cooled trapped atomic ions are one of the most promising platforms for general-purpose quantum computing. Magnetic field-insensitive ‘clock states’ and near-infinite lifetimes allow for minute-long memory coherence times as well as qubit frequencies that are in the convenient microwave domain [1]. Most work on these qubits has so far focussed on using lasers for gate operations, however there are several schemes that offer the prospect of performing all coherent operations using purely electronic methods [2,3].
These replace lasers with cheaper, smaller, more stable microwave devices with more straightforward phase control. Microwave elements can also be integrated into trapping structures more easily than their optical counterparts for improved scalability. The latest results using near-field microwaves have demonstrated two-qubit gate fidelities of 99.7(1)% [4], as well as single-qubit state preparation, gates, memory and read-out fidelities exceeding 99.9% [1]. I will present the latest results on a new ion trap system being developed to exceed these fidelities whilst incorporating new functional elements. Foremost amongst these will be the addition of an auxiliary ion species and a multi-zone trap to enable arbitrary multi-qubit operations [5]. The important experimental techniques of cryogenic cooling and in-situ surface cleaning have also been incorporated.