Weproposeasingle-stepimplementationofamuti-target-qubitcontrolledphasegatewithonecatstatequbit(cqubit)simultaneouslycontrollingn—1targetcqubits.Thetwologicstatesofac.qubitarerepresentedbytwoorthogonalcatstatesofasinglecavitymode.Inthisproposal,thegateisimplementedwithnmicrowavecavitiescoupledtoasuperconductingtransnionqutrit.Becausethequtritremainsinthegroundstateduringthegateoperation,decoherencecausedduetothequtrit5senergyrelaxationanddephasingisgreatlysuppressed.Thegateimplementationisquitesimplebecauseonlyasingle-stcpoperationisneededandneitherclassicalpulsenormeasurementisrequired.Numericalsimulationsdemonstratethathigh-fidelityrealizationofacontrolledphasegatewithonecqubitsimultaneouslycontrollingtwotargetcqubitsisfeasiblewithpresentcircuitQEDtechnology.Thisproposalcanbeextendedtoawiderangeofphysicalsystemstorealizetheproposedgate,suchasmultiplemicrowaveoropticalcavitiescoupledtoanaturalorartificialthree-levelatom.
