Classical Shadows for Quantum Process Tomography on Near-term Quantum Computers

Ryan Levy | Di Luo | Bryan K. Clark

Quantum process tomography is crucial for understanding quantum channels and characterizing properties of quantum devices. Inspired by recent advances using classical shadows in quantum state tomography, we have developed a classical shadow method for quantum process tomography, ShadowQPT. We have proved rigorous measurement complexity for ShadowQPT and provided new post-processing techniques for improving the accuracy. Furthermore, our approach has been implemented on the IonQ trapped ion quantum computer doing reconstructions for unitary and non-unitary processes of a channel of up to n=4 qubits (equivalent to the complexity of n=8 qubits in state tomography) as well as determining input-output state overlaps. We show that ShadowQPT is efficient and provides new advancement on quantum process tomography in near-term and future quantum devices.

Funding Sources: NSF Quantum Leap Challenge Institute for Hybrid Quantum Architectures and Networks (NSF Award 2016136)|National Science Foundation under Cooperative Agreement PHY-2019786