Abstract: A quantum processing comprises n fixed-frequency quantum circuits of distinct frequencies, where n?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?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?m.

Abstract: Techniques relate to operating a quantum processing device is provided. The device includes at least two fixed-frequency quantum circuits coupled to a frequency-tunable coupler. The frequency of the coupler can be modulated so as to drive at least two selectively addressable energy transitions in the quantum processing device. The method includes modulating the frequency of the coupler so as to drive two first-order energy transitions. This is done so as to transfer (at least partly) an excitation of one of the quantum circuits to at least another one of the quantum circuits, via the tunable coupler. Related quantum processing devices are also provided.

Abstract: Embodiments are directed to a superconducting microwave circuit. The circuit includes a substrate and two electrodes. The latter form an electrode pair dimensioned so as to support an electromagnetic field, which allows the circuit to be operated in the microwave domain. The substrate exhibits a raised portion, which includes a top surface and two lateral surfaces. The top surface connects the two lateral surfaces, which show respective undercuts (on the lateral sides of the raised portions). Each of the electrodes includes a structure that includes a potentially superconducting material. Two protruding structures are accordingly formed, which are shaped complementarily to the respective undercuts. This way, the shaped structure of each of the electrodes protrudes toward the other one of the electrodes of the pair.

Abstract: Embodiments are directed to a superconducting microwave circuit. The circuit includes a substrate and two electrodes. The latter form an electrode pair dimensioned so as to support an electromagnetic field, which allows the circuit to be operated in the microwave domain. The substrate exhibits a raised portion, which includes a top surface and two lateral surfaces. The top surface connects the two lateral surfaces, which show respective undercuts (on the lateral sides of the raised portions). Each of the electrodes includes a structure that includes a potentially superconducting material. Two protruding structures are accordingly formed, which are shaped complementarily to the respective undercuts. This way, the shaped structure of each of the electrodes protrudes toward the other one of the electrodes of the pair.

Abstract: A quantum processing comprises n fixed-frequency quantum circuits of distinct frequencies, where n?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?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?m.

Abstract: A method for operating a quantum processing device is provided including at least two quantum circuits coupled to a tunable coupler, wherein the quantum circuits are subject to cross-talk, the method including: applying a primary signal to the quantum circuits so as to drive one or more energy transitions between states spanned by the quantum circuits; and applying a compensation signal to the tunable coupler, the compensation signal designed so as to shift at least one state spanned by the quantum circuits, in energy, to compensate for cross-talk between the quantum circuits. Related quantum processing devices and chips are also provided.

Abstract: Techniques relate to operating a quantum processing device is provided. The device includes at least two fixed-frequency quantum circuits coupled to a frequency-tunable coupler. The frequency of the coupler can be modulated so as to drive at least two selectively addressable energy transitions in the quantum processing device. The method includes modulating the frequency of the coupler so as to drive two first-order energy transitions. This is done so as to transfer (at least partly) an excitation of one of the quantum circuits to at least another one of the quantum circuits, via the tunable coupler. Related quantum processing devices are also provided.

Abstract: Techniques relate to operating a quantum processing device is provided. The device includes at least two fixed-frequency quantum circuits coupled to a frequency-tunable coupler. The frequency of the coupler can be modulated so as to drive at least two selectively addressable energy transitions in the quantum processing device. The method includes modulating the frequency of the coupler so as to drive two first-order energy transitions. This is done so as to transfer (at least partly) an excitation of one of the quantum circuits to at least another one of the quantum circuits, via the tunable coupler. Related quantum processing devices are also provided.