Non-Markovian Noise Characterization with the Transfer Tensor Method

Abstract

We propose simple protocols for performing quantum noise spectroscopy based on the method of transfer tensor maps (TTM), [Phys. Rev. Lett. 112, 110401 (2014)]. The TTM approach is a systematic way to deduce the memory kernel of a time-nonlocal quantum master equation via quantum process tomography. With access to the memory kernel it is possible to (1) assess the non-Markovianity of a quantum process, (2) reconstruct the noise spectral density beyond pure dephasing models, and (3) investigate collective decoherence in multiqubit devices. We illustrate the usefulness of TTM spectroscopy on the IBM Quantum Experience platform, and demonstrate that the qubits in the IBM device are subject to mild non-Markovian dissipation with spatial correlations.

Transfer-tensor description of memory effects in open-system dynamics and multi-time statistics

“…In this paper, we investigate the relation between the memory effects appearing in an open quantum system dynamics and those associated with the multi-time statistics due to sequential measurements, by means of the transfer tensor (TT) method [35][36][37][38]. We will show that the latter, which was introduced to treat efficiently the long-time dynamics of open quantum systems, also allows one to treat memory effects on the dynamics and the multi-time statistics on a similar footing.…”

Quantum Circuit Engineering for Correcting Coherent Noise

“…In state-of-art quantum processors, two-qubit gates are at least order of magnitude noisier than their single-qubit counterparts and limit the fidelity of quantum circuit [1][2][3][4]. Higher operational inaccuracy is not the only bottleneck of state fidelity, action of CNOT gates sequence adds to several context-dependent noise sources including crosstalk [5], coherent/systematic errors [6,7], correlated errors [8] and non-markovian bath [9,10]. These are some examples of unforeseen errors [11] mostly unfolding during the execution of quantum circuit.…”

Extending comb-based spectral estimation to multiaxis quantum noise

“…In recent years, a large focus of QNS has been on characterizing dephasing noise, that is, noise that couples exclusively along the system's quantization axis and results in transverse relaxation ("T 2 effects") -under the assumption that any additional, off-axis noise source is either a priori negligible or the resulting longitudinal relaxation ("T 1 effects") can be parametrically incorporated within an ad hoc, phenomenological model. Though more general noise models have been characterized in contexts where off-axis contributions are tunable [2] or using full quantum process tomography [14], most QNS protocols to date involve single-axis spectral estimation. These methods have been developed and implemented following two main paradigms: multipulse ap- * These authors contributed equally to this manuscript.…”