Fast Gates

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Trapped-ion devices have demonstrated, on a small number of qubits, all the building-blocks required to build a quantum computer with precision better than any competing technology. However the speed of these devices, limited by the entangling gates, has not increased commensurately. The aim of this project is to change this by exploiting optical phase control to significantly speed up trapped-ion entangling gates whilst also removing several currently limiting fundamental sources of error.In preliminary work, we have recently demonstrated the first high-speed entangling logic gates for trapped-ion qubits [Schafer et al., Nature 555, 75 (2018)]. We achieved a fidelity of 99.8% for a 1.6 microsecond gate time, close to the highest reported two-qubit gate fidelities of 99.9%, but more than an order of magnitude faster. Over the course of this project we will extend this proof-of-concept technique to demonstrate the first high-speed control of multi-qubit registers.The project will involve both experimental and theoretical work, including:- developing and numerically modelling phase-controlled fast entangling gate dynamics- building a new apparatus optimised for high-speed multi-qubit entangling gates- sophisticated classical control techniques to precisely control the optical interaction phase of multi-qubit register