Multi-time quantum process tomography on a superconducting qubit

Abstract

Current quantum technologies are at the cusp of becoming useful, but still face formidable obstacles such as noise. Noise severely limits the ability to scale quantum devices to the point that they would offer an advantage over classical devices. To understand the sources of noise it is necessary to fully characterise the quantum processes occurring across many time steps; only this would reveal any time-correlated noise called non-Markovian. Previous efforts have attempted such a characterisation but obtained only a limited reconstruction of such multi-time processes. In this work, we fully characterise a multi-time quantum process on superconducting hardware using in-house and cloud-based quantum processors. We achieve this by employing sequential measure-and-prepare operations combined with post-processing. Employing a recently developed formalism for multi-time processes, we detect general multi-time correlated noise. We also detect quantum correlated noise which demonstrates that part of the noise originates from quantum sources, such as physically nearby qubits on the chip.

13 pages, 5 figures, 5 tables

References in corpus (39)

• Measure for the Degree of Non-Markovian Behavior of Quantum Processes in Open Systems
• Non-Markovian dynamics in open quantum systems
• Entanglement and non-Markovianity of quantum evolutions
• Quantum Non-Markovianity: Characterization, Quantification and Detection
• Quantum information processing with circuit quantum electrodynamics
• Quantum correlations with no causal order
• Theoretical framework for quantum networks
• Universal control of a six-qubit quantum processor in silicon
• Non-Markovian quantum processes: complete framework and efficient characterisation
• Non-Markovian quantum jumps
• On measures of non-Markovianity: divisibility vs. backflow of information
• Quantum causal modelling
• Gate Set Tomography
• Witnessing causal nonseparability
• Causal and causally separable processes
• Demonstration of non-Markovian process characterisation and control on a quantum processor
• Toward a general theory of quantum games
• Multiqubit Spectroscopy of Gaussian Quantum Noise
• Removing leakage-induced correlated errors in superconducting quantum error correction
• Non-Markovian Quantum Process Tomography
• Efficient exploration of Hamiltonian parameter space for optimal control of non-Markovian open quantum systems
• Quantum process tomography via completely positive and trace-preserving projection
• Analysing correlated noise on the surface code using adaptive decoding algorithms
• Optimized electrical control of a Si/SiGe spin qubit in the presence of an induced frequency shift
• Updating the Born rule
• Witnessing quantum memory in non-Markovian processes
• Reconstructing open quantum system dynamics with limited control
• Experimental characterisation of a non-Markovian quantum process
• Randomized benchmarking for non-Markovian noise
• A quantum causal discovery algorithm
• Extending comb-based spectral estimation to multiaxis quantum noise
• Quantum Markovianity as a supervised learning task
• Ramsey Interferometry in Correlated Quantum Noise Environments
• Non-Markovian memory in IBMQX4
• Non-Markovian Quantum Gate Set Tomography
• What can unitary sequences tell us about multi-time physics?
• Memory in quantum dot blinking
• Numerical evaluation of the fidelity error threshold for the surface code
• Unifying non-Markovian characterisation with an efficient and self-consistent framework