Multi-sample system for emulating a quantum computer and methods for use therewith

1. A system for emulating sampling of a quantum computer having a plurality of qubits arranged in a grid topology with N columns, the system comprising:

a memory that stores operational instructions;

at least one classical processor that is configured by the operational instructions to perform operations, the operations including:

producing final weights and variable assignments for the N columns based on N iterative passes through the grid topology, wherein each of the N iterative passes generates preliminary weights and variable assignments for a number of columns of the N columns based on preliminary weights and variable assignments generated for an adjacent column for each of the number of columns, wherein final weights and variable assignments are generated for a final column of the N columns for each of the N iterative passes based on the preliminary weights and variable assignments generated for a column of the N columns adjacent to the final column of the N columns, wherein the final weights and variable assignments for the final column of the N columns are used in a next successive pass of the N iterative passes to reduce the number of columns of the N columns where the preliminary weights and variable assignments are regenerated until the N iterative passes are complete and final weights and variable assignments for each of the N columns have been generated;

wherein the sampling of the quantum computer having the plurality of qubits is emulated by producing a plurality of samples from the N iterative passes based on the final weights and variable assignments for each of the N columns.

2. The system of claim 1 , wherein the plurality of samples includes k samples and wherein the sampling includes:

for each sample s l , choosing a random number a l uniformly between zero and the preliminary weight of the assignment of s l in column j+1 of the N columns, wherein j is an integer and l is an integer between 1 and k;

wherein the generation of the preliminary weights and variable assignments includes, increasing an assignment s in column j+1 of the N columns by the preliminary weight of an assignment t in a column j of the N columns; and

decrement a l by the preliminary weight of the assignment t in the column j and when this results in s l going from positive to non-positive, set a final weight of the assignment in the column j of the final weights to t.

3. The system of claim 1 , wherein a first iterative pass of the N iterative passes generates the final weights and variable assignments for an Nth column of the N columns, based on the preliminary weights and variable assignments generated for a (N−1)st column of the N columns.

4. The system of claim 3 , wherein the number of the N columns associated with the first iterative pass of the N iterative passes includes all columns of the N columns in a range between a second column of the N columns and the (N−1)st column of the N columns.

5. The system of claim 3 , wherein the first iterative pass of the N iterative passes generates the preliminary weights and variable assignments for a first column of the N columns, based on null weights corresponding to a null column.

6. The system of claim 3 , wherein the last iterative pass of the N iterative passes generates the final weights and variable assignments for a first column of the N columns, based on the final weights and variable assignments for a second column of the N columns.

7. The system of claim 1 , wherein a pth iterative pass of the N iterative passes generates the final weights and variable assignments for an (N−p+1)st column of the N columns, based on the preliminary weights and variable assignments generated for a (N−p)th column of the N columns.

8. The system of claim 7 , wherein the number of the N columns associated with the pth iterative pass of the N iterative passes includes all columns of the N columns in a range between a second column of the N columns and the (N−p)th column of the N columns.

9. The system of claim 1 , wherein the grid topology corresponds to a quadratic unconstrained binary optimization (QUBO) model.

10. The system of claim 1 , wherein the plurality of samples each corresponds to a Boltzmann distribution.

11. A method for emulating sampling of a quantum computer having a plurality of qubits arranged in a grid topology with N columns, the method comprising:

performing a first iterative pass of N iterative passes through the grid topology to produce final weights and variable assignments for an Nth column of the N columns, by generating preliminary weights and variable assignments for N−1 columns of the N columns based on preliminary weights and variable assignments generated for an adjacent column for each of the N−1 columns, wherein the final weights and variable assignments are generated for an Nth column based on the preliminary weights and variable assignments generated for an (N−1)st column of the N columns adjacent to the Nth column;

performing N−1 other iterative passes of the N iterative passes through the grid topology by:

(a) setting p=2;

(b) performing an pth pass through the grid topology, to produce final weights and variable assignments for the (N−p+1)st column of the N columns, by regenerating preliminary weights and variable assignments for N−p columns of the N columns based on preliminary weights and variable assignments regenerated for an adjacent column for each of the N−p columns, wherein final weights and variable assignments are generated for an (N−p+1)st column based on the preliminary weights and variable assignments regenerated for an (N−p)th column of the N columns adjacent to the (N−p+1)st column and the final weights and variable assignments generated for the (N−p+2)nd column;

(c) incrementing p;

(d) repeating steps (b) and (c) until p=N; and

(e) performing a final pass through the grid topology, to produce the final weights and variable assignments for a first column of the N columns, based on the final weights and variable assignments generated for a second column of the N columns;

wherein the sampling of the quantum computer having the plurality of qubits is emulated by producing a plurality of samples from the N iterative passes based on the final weights and variable assignments for each of the N columns.

12. The method of claim 11 , wherein the plurality of samples includes k samples and wherein the sampling includes:

for each sample s l , choosing a random number a l uniformly between zero and the preliminary weight of the assignment of s l in column j+1 of the N columns, wherein j is an integer and l is an integer between 1 and k;

wherein the generation of the preliminary weights and variable assignments includes, increasing an assignment s in column j+1 of the N columns by the preliminary weight of an assignment t in a column j of the N columns; and

decrement a l by the preliminary weight of the assignment t in the column j and when this results in s l going from positive to non-positive, set a final weight of the assignment in the column j of the final weights to t.

13. The method of claim 11 , wherein a first iterative pass of the N iterative passes generates the final weights and variable assignments for an Nth column of the N columns, based on the preliminary weights and variable assignments generated for a (N−1)st column of the N columns.

14. The method of claim 13 , wherein the number of the N columns associated with the first iterative pass of the N iterative passes includes all columns of the N columns in a range between a second column of the N columns and the (N−1)st column of the N columns.

15. The method of claim 13 , wherein the first iterative pass of the N iterative passes generates the preliminary weights and variable assignments for a first column of the N columns, based on null weights corresponding to a null column.

16. The method of claim 13 , wherein the last iterative pass of the N iterative passes generates the final weights and variable assignments for a first column of the N columns, based on the final weights and variable assignments for a second column of the N columns.

17. The method of claim 11 , wherein a pth iterative pass of the N iterative passes generates the final weights and variable assignments for an (N−p+1)st column of the N columns, based on the preliminary weights and variable assignments generated for a (N−p)th column of the N columns.

18. The method of claim 17 , wherein the number of the N columns associated with the pth iterative pass of the N iterative passes includes all columns of the N columns in a range between a second column of the N columns and the (N−p)th column of the N columns.

19. The method of claim 11 , wherein the grid topology corresponds to a quadratic unconstrained binary optimization (QUBO) model.

20. A system for emulating sampling of a quantum computer having a plurality of qubits arranged in a grid topology with N columns, the system comprising:

a memory that stores operational instructions;

at least one classical processor that is configured by the operational instructions to perform operations, the operations including:

performing a first pass through the grid topology, wherein the first pass includes iteratively generating preliminary weights and variable assignments for N−1 columns of the N columns based on preliminary weights generated for a preceding adjacent column for each of the N−1 columns in a first order from a first column in the N columns to a (N−1)st column of the N columns, wherein final weights are generated for the Nth column based on the preliminary weights generated for a (N−1)st column of the N columns; and

performing a second pass through the grid topology by producing final weights and variable assignments for the remaining N−1 columns of the N columns, wherein the second pass includes iteratively generating final weights and variable assignments for N−1 columns of the N columns based on final weights generated for a preceding adjacent column for each of the N−1 columns in a second order from the (N−1)st column of the N columns to the first column of the N columns;

wherein the sampling of the quantum computer having the plurality of qubits is emulated by a sample based on the final weights and variable assignments for each of the N columns.