Fast quantum gates with first-order transitions via frequency-modulated tunable coupling element

A method of operating a quantum processing device, the method comprising:

• modulating a frequency of a tunable coupler so as to drive two first-order energy transitions, wherein the quantum processing device comprises at least two fixed frequency quantum circuits coupled to the tunable coupler;
• and
• causing an excitation of one of the at least two fixed frequency quantum circuits such that the excitation is at least partly transferred to at least another one of the at least two fixed frequency quantum circuits, via the tunable coupler;
• wherein the frequency of the tunable coupler is modulated so as to implement a quantum gate operating on at least one of the at least two fixed frequency quantum circuits;
• wherein the frequency of the tunable coupler is modulated at a first frequency, so as to drive a first transition and thereby transfer, at least partly, a first excitation of the one of the at least two fixed frequency quantum circuits to the tunable coupler.