Robust quantum state transfer using tunable couplers

TL;DR

This paper demonstrates a robust quantum state transfer method between resonators using tunable couplers and destructive interference, achieving over 99% efficiency with precise frequency compensation.

Contribution

It introduces a robust transfer protocol utilizing adjustable couplers and interference, addressing parameter variations and noise effects in quantum state transfer.

Findings

Nearly perfect transfer efficiency with tunable couplers.

Robustness to parameter variations and noise effects.

High sensitivity to frequency mismatch requiring active compensation.

Abstract

We analyze the transfer of a quantum state between two resonators connected by a superconducting transmission line. Nearly perfect state-transfer efficiency can be achieved by using adjustable couplers and destructive interference to cancel the back-reflection into the transmission line at the receiving coupler. We show that the transfer protocol is robust to parameter variations affecting the transmission amplitudes of the couplers. We also show that the effects of Gaussian filtering, pulse-shape noise, and multiple reflections on the transfer efficiency are insignificant. However, the transfer protocol is very sensitive to frequency mismatch between the two resonators. Moreover, the tunable coupler we considered produces time-varying frequency detuning caused by the changing coupling. This detuning requires an active frequency compensation with an accuracy better than 90% to yield the transfer efficiency above 99%.