Felix Motzoi

Aarhus University, Denmark

Counter-diabatic methods for high-fidelity quantum logic gates

Abstract

 

As developments continue to build larger quantum computing architectures and to make logic gates faster and more accurate, resonant transitions within these system tend to become more crowded in frequency space and it becomes challenging to uniquely address them.  Time-dependent external fields that manipulate quantum information in this way will cause state population to dissipate into unwanted parts of the Hilbert space, which, according to the adiabatic theorem, limits how fast gates can be performed within the coherence time of the system.  Fortunately, methods have been developed over the last twenty years for so-called counter-diabatic corrections to ideal adiabatic trajectories.  Most simply, such correction can allow transitionless state transfer or phase accumulation along a particular adiabatic trajectory.  However, in the context of quantum computing, another important use is in the suppression of unwanted transitions in the vicinity of a resonantly operated gate.  In particular, we examine here the elimination of leakage in superconducting qubit gates using the DRAG protocol, crosstalk removal in frequency multiplexed qubit control buses, and addressing frequency-crowded Rydberg transitions for two-qubit neutral atom entanglement.  We conclude by generalizing the higher-order superadiabatic expansion by augmenting it via counter-diabatic terms of different derivative degree, which can allow solving a much broader class of spectral problems, whereby the expansion can now converge to arbitrary accuracy for finite evolution time.



Date: 3/7/2017
Time:12:00 (coffee & cookies will be served at 11:45)
Place:FORTH Seminar Room 1