Arrangement of memory cells for a quantum-computing device
An array of interconnected memory cells for storing therein a fractional-quantum-Hall-effect droplet whose state is controllable using voltages applied to the cell electrodes. In an example embodiment, the memory cells are arranged and linked together such as to reduce the geometric size of the array, e.g., compared to that of a linear array having the same number of memory cells. For example, one or more wheel-and-spokes arrangements of the memory cells can be used for this purpose. The smaller geometric size of the array can result in better coherence across the droplet confined therein, which can advantageously be used to improve the reliability and/or performance of the corresponding quantum-computing device.
1. An apparatus, comprising:
a planar semiconductor quantum-well structure having layers extending along a top surface thereof;
a plurality of memory cells, each of the memory cells having a first pattern of controllable electrodes over and near the top surface, the electrodes of the first pattern substantially laterally surrounding a corresponding physical sequence of three or more lateral regions of the semiconductor quantum-well structure joined by channels; and
one or more memory-cell linkers configurable to link the memory cells, each of said one or more memory-cell linkers having a respective second pattern of controllable electrodes over and near the top surface; and
wherein the electrodes of the first and second patterns are controllable to deplete underlying lateral areas of the quantum-well structure of charge carriers such that a droplet of the charge carriers in the semiconductor quantum-well structure is localized laterally along the top surface, the electrodes of the one or more second patterns being controllable to confine a portion of the droplet, along the top surface within the one or more memory-cell linkers, to connect at least three of the memory cells; and
wherein at least one of the one or more memory-cell linkers is configurable to support entanglement of a fractional-quantum-Hall-effect state of a part of the droplet in said at least three of the memory cells and the at least one of the one or more memory-cell linkers.
2. The apparatus of claim 1 , wherein a first of the one or more memory-cell linkers is configurable to laterally confine, along the top surface, a part of the droplet to connect four of the memory cells.
3. The apparatus of claim 2 , wherein the four of the memory cells are arranged such that any two laterally adjacent ones of the four of the memory cells are oriented at a relative angle of about 90 degrees.
4. The apparatus of claim 1 , wherein a first of the one or more memory-cell linkers is configurable to laterally confine, along the top surface, a part of the droplet to connect eight of the memory cells.
5. The apparatus of claim 4 , wherein the eight of the memory cells are arranged such that any two laterally adjacent ones of the eight of the memory cells are oriented at a relative angle of about 45 degrees.
6. The apparatus of claim 1 , further comprising an additional memory-cell linker having a third pattern of electrodes over and near the top surface, the third pattern of electrodes being configurable to laterally confine, along the top surface, a different portion of the droplet to directly connect two of the memory cells.
7. The apparatus of claim 6 , wherein the one or more memory-cell linkers further include a third memory-cell linker.
8. The apparatus of claim 6 , wherein the additional memory-cell linker is configurable to laterally confine, along the top surface, the different portion of the droplet to directly connect thereto one of the at least three of the memory cells.
9. The apparatus of claim 1 , wherein said at least three of the memory cells include two of the memory cells whose orientations are not collinear.
10. The apparatus of claim 9 , wherein said at least three of the memory cells include three of the memory cells whose orientations are about collinear.
11. An apparatus comprising:
a planar semiconductor quantum-well structure having layers extending along a top surface thereof;
a plurality of memory cells, each of the memory cells having a first pattern of controllable electrodes over and near the top surface, the electrodes of the first pattern substantially laterally surrounding a corresponding physical sequence of three or more lateral regions of the semiconductor quantum-well structure joined by channels; and
one or more memory-cell linkers configurable to link the memory cells, each of said one or more memory-cell linkers having a respective second pattern of controllable electrodes over and near the top surface; and
wherein the electrodes of the first and second patterns are controllable to deplete underlying lateral areas of the quantum-well structure of charge carriers such that a droplet of the charge carriers in the semiconductor quantum-well structure is localized laterally along the top surface, the electrodes of the one or more of the second patterns being controllable to confine a portion of the droplet, along the top surface within the one or more memory-cell linkers, to connect at least three of the memory cells; and
wherein the electrodes are controllable to perform one or more of the following:
store a multi-qubit state on the droplet, while the droplet is maintained in a fractional-quantum-Hall-effect state;
read qubit values stored in the memory cells; and
do an entanglement computation with said multi-qubit state stored on the droplet.
12. The apparatus of claim 11 , wherein the electrodes are controllable to perform two or more of the following:
the store of a multi-qubit state on the droplet, while the droplet is maintained in a fractional-quantum-Hall-effect state;
the read of qubit values stored in the memory cells; and
the doing of an entanglement computation with said multi-qubit state stored on the droplet.
13. The apparatus of claim 11 , wherein the electrodes are controllable to perform the following:
the store of a multi-qubit state on the droplet, while the droplet is maintained in a fractional-quantum-Hall-effect state;
the read of qubit values stored in the memory cells; and
the doing of an entanglement computation with said multi-qubit state stored on the droplet.