Experiments using the largest IBM Q quantum computers

As a result of these activities, Adam Mickiewicz University in Poznań, the Centre for Theoretical Physics of the Polish Academy of Sciences, the Institute of Theoretical and Applied Informatics of the Polish Academy of Sciences, and the National Centre for Nuclear Research (NCBJ) in Świerk have already become institutional members of the IBM Quantum Network. Several new teams from Polish universities plan to complete the first phase of experiments in close collaboration with the PSNC. In addition, a number of experiments have been carried out as part of the R&D work carried out directly by the PSNC teams using the largest real IBM Q quantum computers. Different approaches and new quantum methods have been tested, including experimentally investigating the impact of using different types of quantum optimisation algorithms – QAOA (Quantum Approximate Optimisation Algorithm), Quantum Optimisation Optimisation Approach and QAOA with Educated Guess strategy. The results demonstrated the applicability of quantum algorithms in solving test optimisation problems, such as task serialisation problems, and the use of quantum algorithms in complex air traffic safety management problems.

As part of the remote use of the physical resources of IBM Q quantum computers available through the IBM Quantum Innovation Center, the Center for Theoretical Physics of the Polish Academy of Sciences has developed an effective method for characterising readout errors. Currently, readout errors contribute significantly to the overall noise affecting the performance of available quantum computers, and full characterisation of the overall readout noise is not feasible for devices consisting of a large number of qubits. The new method proposed by the Centre for Theoretical Physics of the Polish Academy of Sciences is efficient because it scales logarithmically with the number of qubits, so it can be used to characterise the measurement errors of quantum devices consisting of many qubits. The new method has been successfully implemented and used experimentally to characterise the measurement errors of the 127-qubit IBM Q quantum computers Cusco, Sherbrooke, Brisbane and Nazca. The results obtained allow the construction of a correlated measurement error model, and the reconstructed measurement error models were used to perform an error mitigation procedure.