Group seminar at MPQ and Zoom: Scalable Qubit Arrays for Quantum Computation and Optimisation

August 22, 2023

Boyko Nicolov, Strathclyde University Glasgow
Group seminar at MPQ lecture hall and Zoom
Tuesday, August 22, 09:00 am (MEZ)

Worldwide efforts to develop useful quantum computing and simulation platforms are accelerating at a rapid pace with the long-term goal of realising fault-tolerant platforms that are capable of running flagship quantum algorithms with a demonstrable quantum advantage over classical systems. Presently, one of the major barriers to achieving this are the limited number of high-quality qubits available on a single device. Amongst the different hardware platforms under development, arrays of neutral atoms have demonstrated the best scalability so far with system sizes exceeding 200 identical qubits  with coherence time to gate duration ratios >100 [1]. The recently demonstrated 99.5% CZ gate fidelity using Rydberg dipole-dipole interactions between atoms separated by a few μm addresses one main historical limitation of the neutral atom approach and opens the door towards error correction [2]. With this goal in mind, there is a renewed effort in developing techniques to speed up state detection and make it non-destructive in order to satisfy the midcircuit readout requirement of many existing error correction algorithms.

We present progress towards a new experimental platform for quantum computation at the University of Strathclyde based on reconfigurable atom arrays of up to 225 133Cs atoms that addresses some of these challenges supported by an EPSRC Prosperity Partnership SQuAre with M Squared Lasers Ltd. We demonstrate high fidelity single qubit gate operations with errors below the threshold for fault  tolerance using a non-destructive readout technique [3], along with work towards simultaneous trapping of arrays of ground and Rydberg states that could extend the accessible circuit depths by taking full advantage of the long Rydberg lifetimes. These results pave the way towards performing high-fidelity two qubit and multi-qubit gate operations using a novel adiabatic rapid passage protocol [4] developed at Strathclyde, as well as exploring applications of the neutral atom system to solving classical optimisation problems such as the maximum independent set (MIS) in the analogue and digital quantum  computing regimes.

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