Systems and devices for quantum processor topology
Topologies for analog processors may include cells comprising at least portions of qubits and couplers. Qubits and couplers may be shared among or extend across multiple cells. A cell may include four sets of partial qubits, and partial qubits may form whole qubits with partial qubits in adjacent cells. First and second sets of partial qubits may include partial qubits that extend substantially parallel to one another and along a first direction. Third and fourth sets may include partial qubits that extend substantially parallel to one another and along a second direction. Each partial qubit in the first and second sets may cross, and be substantially orthogonal to, at least one partial qubit from each of the third and fourth sets. A cell may include first and second sets of intra-cell couplers, and partial couplers that form inter-cell couplers with partial couplers in adjacent cells.
1 . A quantum processor comprising:
a plurality of cells tiled over an area such that each cell of the plurality of cells is positioned proximately adjacent at least one other cell of the plurality of cells, each cell comprising:
a plurality of partial qubits, wherein each partial qubit in the plurality of partial qubits comprises at least a portion of a length of a whole qubit, the plurality of partial qubits comprising:
a first set of partial qubits, each partial qubit in the first set of partial qubits extending substantially along a first direction,
a second set of partial qubits, each partial qubit in the second set of partial qubits extending substantially along the first direction, wherein each partial qubit in the second set of partial qubits is substantially parallel with each partial qubit in the first set of partial qubits,
a third set of partial qubits, each partial qubit in the third set of partial qubits extending substantially along a second direction, wherein each partial qubit in the third set of partial qubits crosses at least one partial qubit in the first set of partial qubits and at least one partial qubit in the second set of partial qubits, and
a fourth set of partial qubits, each partial qubit in the fourth set of partial qubits extending substantially along the second direction, wherein each partial qubit in the fourth set of partial qubits is substantially parallel with each partial qubit in the third set of partial qubits, and wherein each partial qubit in the fourth set of partial qubits crosses at least one partial qubit in the first set of partial qubits and at least one partial qubit in the second set of partial qubits;
a first set of couplers, wherein each coupler in the first set of couplers communicatively couples a partial qubit of the plurality of partial qubits extending substantially along the first direction and a partial qubit of the plurality of partial qubits extending substantially along the second direction; and
a second set of couplers, wherein each coupler in the second set of couplers communicatively couples a partial qubit in the first set of partial qubits to a partial qubit in the second set of partial qubits, or a partial qubit in the third set of partial qubits to a partial qubit in the fourth set of partial qubits; and
a set of inter-cell couplers, each inter-cell coupler of the set of inter-cell couplers communicatively couplingcouples two partial qubits in adjacent cells of the plurality of cells wherein the two partial qubits belong to a same one of a respective first, second, third, or fourth set of partial qubits of each one of the adjacent cells.
2 . The quantum processor of claim 1 , wherein partial qubits of the plurality of partial qubits extending substantially along the first direction are substantially orthogonal to partial qubits of the plurality of partial qubits extending substantially along the second direction.
3 . The quantum processor of claim 1 , wherein each partial qubit in at least one of the first set of partial qubits, the second set of partial qubits, the third set of partial qubits, and the fourth set of partial qubits comprises half of the length of a whole qubit.
4 . The quantum processor of claim 1 , wherein at least one set of partial qubits in each cell of the plurality of cells forms a set of whole qubits with a set of partial qubits in an adjacent cell of the plurality of cells.
5 . The quantum processor of claim 3 , wherein each whole qubit in a set of whole qubits spans a majority of a length of two cells of the plurality of cells.
6 . The quantum processor of claim 1 , wherein:
the partial qubits of the first set of partial qubits extend substantially parallel to a first major axis, the first major axis extending substantially along the first direction;
the partial qubits of the second set of partial qubits extend substantially parallel to a second major axis along a second major axis, the second major axis extending substantially along the first direction;
the partial qubits of the third set of partial qubits extend substantially parallel to a third major axis, the third major axis extending substantially along the second direction; and
the partial qubits of the fourth set of partial qubits extend substantially parallel to a fourth major axis, the fourth major axis extending substantially along the second direction,
wherein both of the first major axis and the second major axis cross both of the third major axis and the fourth major axis.
7 . The quantum processor of claim 6 , wherein pairs of crossing major axes are substantially orthogonal to one another.
8 . The quantum processor of claim 1 , wherein:
each partial qubit of the first set of partial qubits extends substantially parallel to a respective first major axis, each respective first major axis extending substantially along the first direction, wherein each respective first major axis is parallel to all other first major axes of other partial qubits in the first set of partial qubits;
each partial qubit of the second set of partial qubits extends substantially parallel to a respective second major axis, each respective second major axis extending substantially along the first direction, wherein each respective second major axis is parallel to all other second major axes of other partial qubits in the second set of partial qubits and the first major axis of the partial qubits in the first set of partial qubits;
each partial qubit of the third set of partial qubits extends substantially parallel to a respective third major axis, each respective third major axis extending substantially along the second direction, wherein each respective third major axis is parallel to all other third major axes of other partial qubits in the third set of partial qubits; and
each partial qubit of the fourth set of partial qubits extends substantially parallel to a respective fourth major axis, each respective fourth major axis extending substantially along the second direction, wherein each respective fourth major axis is substantially parallel to all other fourth major axes of other partial qubits in the fourth set of partial qubits and the third major axis of the partial qubits in the third set of partial qubits.
9 . The quantum processor of claim 8 , wherein:
each respective first major axis of each partial qubit in the first set of partial qubits crosses: at least one third major axis and at least one fourth major axis;
each respective second major axis of each partial qubit in the second set of partial qubits crosses: at least one third major axis and at least one fourth major axis;
each respective third major axis of each partial qubit in the third set of partial qubits crosses: at least one first major axis and at least one second major axis; and
each respective fourth major axis of each partial qubit in the fourth set of partial qubits crosses: at least one first major axis and at least one second major axis.
10 . The quantum processor of claim 9 , wherein each pair of crossing major axes are substantially orthogonal to one another.
11 . The quantum processor of claim 1 , wherein each coupler in the first set of couplers is positioned at a region proximate to a location at which the partial qubit extending substantially along the first direction meets the partial qubit extending substantially along the second direction.
12 . The quantum processor of claim 1 , wherein;
each coupler in the second set of couplers communicatively couples each partial qubit in the first set of partial qubits to a nearest-neighboring partial qubit in the second set of partial qubits, or
each coupler in the second set of couplers communicatively couples each partial qubit in the third set of partial qubits to a nearest-neighboring partial qubit in the fourth set of partial qubits.
13 . The quantum processor of claim 1 , wherein each whole qubit is a superconducting flux qubit.
14 . The quantum processor of claim 13 , wherein each whole qubit comprises:
a Josephson junction;
a first qubit loop formed by a first superconducting current path; and
a second qubit loop formed by a second superconducting current path,
wherein the first qubit loop and the second qubit loop are electrically coupled in parallel across the Josephson junction, and
wherein the first qubit loop and the second qubit loop each comprise a material that exhibits superconducting behavior at and below a critical temperature.
15 . The quantum processor of claim 14 , wherein the Josephson junction is selected from a group consisting of: a compound Josephson junction and a compound-compound Josephson junction.
16 . The quantum processor of claim 14 , wherein the first qubit loop and the second qubit loop are substantially symmetric about an axis of the Josephson junction, the axis of the Josephson junction intersecting:
a first connection between the first qubit loop, the second qubit loop, and the Josephson junction, and
a second connection between the first qubit loop, the second qubit loop, and the Josephson junction.