International Business Machines Corporation
Multi-qubit entangling gate using a frequency-modulated tunable coupler

Abstract:

A quantum processing comprises n fixed-frequency quantum circuits of distinct frequencies, where n.gtoreq.3. The device further comprises a frequency-tunable coupler, designed in such a manner that its frequency can be concomitantly modulated at m frequencies, where m.gtoreq.2, and wherein said m frequencies correspond, each, to a difference of energy between a respective pair of quantum states spanned by the quantum circuits. The quantum circuits are, each, coupled to the tunable coupler. The method may rely on modulating the frequency of the tunable coupler concomitantly at said m frequencies. This, for example, is done so as to drive m energy transitions between connected pairs of states spanned by the quantum circuits and achieve an entangled state of the quantum circuits as a superposition of l states spanned by the quantum circuits, l.gtoreq.m.