Brian Tarasinski

Machine-learning-assisted correction of correlated qubit errors in a topological code

A fault-tolerant quantum computation requires an efficient means to detect and correct errors that accumulate in encoded quantum information. In the context of machine learning, neural networks are a promising new approach to quantum error correction. Here we show that a recurrent neural network can be trained, using only experimentally accessible data, to detect errors in a widely used topological code, the surface code, with a performance above that of the established minimum-weight perfect matching (or blossom) decoder. The performance gain is achieved because the neural network decoder can detect correlations between bit-flip (X) and phase-flip (Z) errors. The machine learning algorithm adapts to the physical system, hence no noise model is needed. The long short-term memory layers of the recurrent neural network maintain their performance over a large number of quantum error correction cycles, making it a practical decoder for forthcoming experimental realizations of the surface code.

Quench dynamics of fermion-parity switches in a Josephson junction

A Josephson junction may be driven through a transition where the superconducting condensate favors an odd over an even number of electrons. At this switch in the ground-state fermion parity, an Andreev bound state crosses through the Fermi level, producing a zero-mode that can be probed by a point contact to a grounded metal. We calculate the time-dependent charge transfer between superconductor and metal for a linear sweep through the transition. One single quasiparticle is exchanged with charge

Adaptive Weight Estimator for Quantum Error Correction in a Time-Dependent Environment

Q

A qubit-based oscilloscope for characterizing the distortion of flux pulses for two-qubit gates in circuit QED

depending on the coupling energies

Adaptive Weight Estimator for Quantum Error Correction in a Time-Dependent Environment (Adv. Quantum Technol. 1/2018)

\gamma_1,\gamma_2

Adaptive weight estimator for quantum error correction

of the metal to the Majorana operators of the zero-mode. For a single-channel point contact,

Hybrid Epitaxial InAsSb/Al Nanowires Towards Topological Applications

Q

Simulating a transmon implementation of the surface code, Part II

equals the electron charge

Topological phase transition of a Josephson junction and its dynamics

e

Majorana Gun: An On-Demand Single-Majorana Fermion Source

in the adiabatic limit of slow driving, while in the opposite quenched limit