CSI Q Seminar

In the noisy intermediate-scale quantum (NISQ) era, it is vital to characterize the performance of the device and mitigate the noise. In this talk I will start with our detector tomography experiment carried out on IBM quantum computers, and how the results can be used to mitigate readout noise. In addition to the readout noise, there are other errors associated with state preparation and quantum gates, potentially with spatial and/or temporal crosstalk. Consequently, tomography experiments become inefficient as the circuit becomes large. To address the overall noise present in quantum circuits, we introduce a method to characterize circuit performance by evaluating the quadratic error loss function or the final state fidelity loss. I will discuss both the numerical simulation and the experimental demonstration on a superconducting device. The quadratic error loss function can also be utilized in the error mitigation method named quasiprobability representation. We propose to learn the mitigation scheme by optimizing a suitably chosen loss function and demonstrate the training process by numerical simulation.