Superconducting quantum circuits

Abstract

To provide a superconducting quantum circuit including four-body interaction coupler that has an excellent noise resistance characteristic and is applicable to an actual application.SOLUTION: A four-body interaction coupler, in a planer circuit configuration, comprises a first electrode and a second electrode disposed facing each other and away from a circumambient ground pattern, the first electrode being provided with a first facing part and a second facing part that extend from a portion of the first electrode different from the side facing the second electrode toward sides of a first quantum bit and a second quantum bit, respectively, the second electrode being provided with a first facing part and a second facing part that extend from a portion of the second electrode different from the side facing the first electrode toward sides of third quantum bit and forth quantum bit, respectively, and provided with a non-liner device including a Josephson junction crosslinking the first electrode and the second electrode, at least one of a gap width between the first electrode and the ground pattern facing the first electrode and a gap width between the second electrode and the ground pattern facing the second electrode is set to a value equal to or a fraction of a size of the first electrode or the second electrode.SELECTED DRAWING: Figure 3

Claims

1. A superconducting quantum circuit comprising a four-body interaction coupler that connects the first to fourth qubits via four-body interaction, The aforementioned tetrabody interaction coupler is The planar circuit configuration includes a first electrode and a second electrode positioned opposite each other and spaced apart from the surrounding ground pattern. The first electrode comprises first and second opposing portions that extend from a location on the first electrode separate from the side facing the second electrode toward the first and second qubits, respectively. The second electrode comprises first and second opposing portions that extend from a location on the second electrode separate from the side facing the first electrode toward the third and fourth qubits, respectively. The device comprises a nonlinear element including a Josephson junction that bridges the first electrode and the second electrode, The gap width between the first electrode and the ground pattern facing the first electrode, and The gap width between the second electrode and the ground pattern facing the second electrode is The size of the first electrode and the second electrode is set to the same order of magnitude or one order of magnitude higher. The first electrode and the second electrode are arranged in a planar shape with their lower bases, which are the longer bases of the first and second trapezoids, spaced apart from each other. The first and second opposing portions of the first electrode extend from the intersection of the upper base and two legs of the first trapezoid, which forms the planar shape of the first electrode, toward the first and second qubits, respectively. The first and second opposing portions of the second electrode extend toward the third and fourth qubits, respectively, from the intersection of the upper base and two legs of the second trapezoid, which forms the planar shape of the second electrode. A superconducting quantum circuit in which the nonlinear element is connected between the ends of the lower bases of the first trapezoid and the second trapezoid, which form the planar shape of the first electrode and the second electrode.

2. A superconducting quantum circuit comprising a four-body interaction coupler that connects the first to fourth qubits via four-body interaction, The aforementioned tetrabody interaction coupler is The planar circuit configuration includes a first electrode and a second electrode positioned opposite each other and spaced apart from the surrounding ground pattern. The first electrode comprises first and second opposing portions that extend from a location on the first electrode separate from the side facing the second electrode toward the first and second qubits, respectively. The second electrode comprises first and second opposing portions that extend from a location on the second electrode separate from the side facing the first electrode toward the third and fourth qubits, respectively. The device comprises a nonlinear element including a Josephson junction that bridges the first electrode and the second electrode, The gap width between the first electrode and the ground pattern facing the first electrode, and The gap width between the second electrode and the ground pattern facing the second electrode is The size of the first electrode and the second electrode is set to be the same as or one order of magnitude larger. In the aforementioned four-body interaction coupler, The first electrode and the second electrode each have a vertical portion extending in one direction and a horizontal portion extending from the end of the vertical portion in a direction perpendicular to the first direction, The vertical portion of the first electrode comprises a plurality of first extended portions that extend toward the vertical portion of the opposing second electrode. The longitudinal portion of the second electrode comprises a plurality of second extended portions that extend toward the longitudinal portion of the opposing first electrode. The first expanded portion of the first electrode and the second expanded portion of the second electrode are arranged nested within each other. A superconducting quantum circuit in which the nonlinear element is connected between the end of the vertical portion of the first electrode and the end of the horizontal portion of the second electrode that is opposite to the end of the vertical portion of the first electrode.

3. In the aforementioned four-body interaction coupler, The first electrode and the second electrode are coupled via a first capacitance that is shunt-connected to the nonlinear element. The first and second opposing portions of the first electrode are coupled to the first and second qubits and the second and third capacitances, The first and second opposing portions of the second electrode are coupled to the third and fourth qubits via the fourth and fifth capacitances. The superconducting quantum circuit according to claim 1 or 2, wherein the first electrode and the second electrode are surrounded by the ground pattern with a gap between them.

4. In the aforementioned four-body interaction coupler, The ground pattern is arranged between the first and second opposing portions of the first electrode and the first and second qubits. The ground pattern is arranged between the first and second opposing portions of the second electrode and the third and fourth qubits. The first electrode and the first and second opposing portions of the first electrode, The superconducting quantum circuit according to claim 2, wherein the second electrode and the first and second opposing portions of the second electrode are all surrounded by the ground pattern.

5. In the aforementioned four-body interaction coupler, The aforementioned nonlinear device is A SQUID (superconducting quantum interference device) is formed by connecting a first superconducting line and a first Josephson junction, and a second superconducting line and a second Josephson junction in a loop. A control line that carries a current to apply a magnetic flux that intersects the loop of the SQUID, A superconducting quantum circuit according to any one of claims 1 to 4, including the above.

6. Each of the first to fourth qubits is, An LC resonant circuit including a SQUID in which a first superconducting line and a first Josephson junction and a second superconducting line and a second Josephson junction are connected in a loop, A control line that carries a current to apply a magnetic flux that intersects the loop of the SQUID, A superconducting quantum circuit according to any one of claims 1 to 5, comprising a first to fourth Josephson parametric oscillator including

7. The superconducting quantum circuit described in claim 6 is A superconducting quantum circuit comprising a quantum computer having the first to fourth Josephson parametric oscillators and the four-body interaction coupler as unit structures.

8. Having multiple of the aforementioned unit structures, The superconducting quantum circuit according to claim 7, wherein the unit structure constitutes a quantum computer in which at least one Josephson parametric oscillator among the first to fourth Josephson parametric oscillators constituting the unit structure is shared with one or more other unit structures.

Images