METHODS AND APPARATUS FOR PARALLEL QUANTUM COMPUTING

1 . A computer-implemented method for controlling a classical computer comprising one or more classically-executable-nodes of a classical-quantum hybrid algorithm, wherein the classical computer is operatively coupled to a quantum computer, the method comprising:

sending, by the one or more classically-executable-nodes, a first-circuit to the quantum computer for evaluation;

receiving a first-circuit-evaluation of the first-circuit from the quantum computer;

processing, by the one or more classically-executable-nodes, the first-circuit-evaluation during a first-time interval;

sending, by the one or more classically-executable-nodes, a second-circuit to the quantum computer for evaluation, by the quantum computer, at least in part during the first-time-interval; and

receiving a second-circuit-evaluation of the second-circuit, from the quantum computer, for processing by the one or more classically-executable-nodes.

2 . The method of claim 1 , further comprising:

processing, by the one or more classically-executable-nodes, the second-circuit-evaluation during a second-time interval;

sending, by the one or more classically-executable-nodes, a third-circuit to the quantum computer for evaluation, by the quantum computer, at least in part during the first-time-interval and/or the second-time-interval; and

receiving a third-circuit-evaluation of the third-circuit, from the quantum computer, for processing by the one or more classically-executable-nodes.

3 . The method of claim 1 , wherein the classical-quantum hybrid algorithm has a structure corresponding to a directed acyclic graph with:

vertices formed from the one or more classically-executable-nodes; and

edges formed from a plurality of quantum-circuits comprising the first-circuit and the second-circuit.

4 . The method of claim 1 , wherein the one or more classically-executable-nodes comprise:

a first-node configured to:

send the first-circuit to the quantum computer;

receive the first-circuit-evaluation from the quantum computer; and

process the first-circuit-evaluation during the first-time interval, and

a second-node, different than the first-node, the second-node configured to:

send the second-circuit to the quantum computer for evaluation at least in part during the first-time-interval;

receive the second-circuit-evaluation from the quantum computer; and

process the second-circuit-evaluation.

5 . The method of claim 1 , further comprising:

tagging the first-circuit with:

a first-node-unique-identifier that uniquely identifies a first-node, of the one or more classically-executable-nodes, sending the first-circuit;

a first-request-unique-identifier that uniquely identifies a request of the first-node for the first-circuit-evaluation;

receiving the first-circuit-evaluation with the first-node-unique-identifier and the first-request-unique-identifier; and

sending the first-circuit-evaluation and the first-request-unique-identifier to the first-node for processing.

6 . The method of claim 1 , further comprising:

tagging the first-circuit with a first-circuit-repeat-count;

sending the first-circuit to the quantum computer for evaluation a plurality of times in accordance with the first-circuit-repeat-count; and

receiving and processing a plurality of first-circuit-evaluations.

7 . The method of claim 1 , further comprising:

sending a plurality of quantum circuits, comprising the first-circuit and the second-circuit, to a circuit-buffer of the classical computer;

selecting a quantum-circuit of the plurality of quantum circuits;

sending, if a value of a buffer-counter satisfies a threshold-value, the selected quantum-circuit to the quantum computer for:

storage in a fixed-length-buffer; and

evaluation by the quantum computer; and

incrementing the value of the buffer-counter by one.

8 . The method of claim 7 , further comprising:

receiving the first-circuit-evaluation of the first-circuit from the quantum computer;

decrementing the value of the buffer-counter by one; and

checking the circuit-buffer for a further quantum-circuit.

9 . The method of claim 7 , wherein the value of the buffer-counter satisfies the threshold-value if the value of the buffer-counter corresponds to a number of quantum-circuits present in the fixed-length-buffer that is less than a capacity of the fixed-length-buffer.

10 . The method of claim 7 , wherein the selecting of the quantum-circuit is based on a selection-policy comprising:

partitioning the plurality of quantum circuits based on identifying, for each respective circuit of a respective partition, a common originating node of the one or more classically-executable-nodes;

determining a number of circuits present in each respective partition; and

determining that the quantum-circuit belongs to a partition with a smallest number of circuits.

11 . The method of claim 1 , further comprising adding one or more new-nodes, to the one or more classically-executable-nodes of the classical-quantum hybrid algorithm, based on the first-circuit-evaluation and/or the second-circuit-evaluation.

12 . The method of claim 1 , wherein the classical-quantum hybrid algorithm is one or more of: a Variational Quantum Eigensolver; an optimization algorithm; and a quantum processor benchmarking algorithm.

13 . A computer-implemented method for controlling a quantum computer comprising a quantum-processor-unit, the method comprising:

receiving a plurality of quantum-circuits from one or more classically-executable-nodes of a classical-quantum hybrid algorithm, wherein the plurality of quantum-circuits comprises a first-circuit and a second-circuit;

evaluating, using the quantum-processor-unit, the first-circuit to determine a first-circuit-evaluation;

sending the first-circuit-evaluation to the at least one or more classically-executable-nodes for processing during a first-time-interval;

evaluating, using the quantum-processor-unit, the second-circuit to provide a second-circuit-evaluation, wherein the evaluating of the second-circuit occurs, at least in part, during the first-time-interval; and

sending the second-circuit-evaluation to the at least one or more classically-executable-nodes for processing during a second-time-interval.

14 . The method of claim 13 , further comprising:

receiving a third-circuit, of the plurality of quantum-circuits, from the one or more classically-executable-nodes;

evaluating, using the quantum-processor-unit, the third-circuit to provide a third-circuit-evaluation, wherein the evaluating of the third-circuit occurs, at least in part, during the first-time-interval and/or the second-time-interval; and

sending the third-circuit-evaluation to the at least one or more classically-executable-nodes for processing.

15 . The method of claim 13 , wherein the first-circuit is received from a first-node of the one or more classically-executable-nodes and the second-circuit is received from a second-node of the one or more classically-executable-nodes and the first-node is different than the second-node.

16 . The method of claim 13 , further comprising:

receiving, from a first-node of the one or more classically-executable-nodes, the first-circuit with:

a first-node-unique-identifier that uniquely identifies first-node;

a first-request-unique-identifier that uniquely identifies a request of the first-node for the first-circuit-evaluation; and

sending the first-circuit-evaluation with the first-node-unique-identifier and the first-request-unique-identifier to the one or more classically-executable-nodes for processing.

17 . The method of claim 13 , further comprising:

receiving the first-circuit with a first-circuit-repeat-count;

evaluating the first-circuit a plurality of times in accordance with the first-circuit-repeat-count; and

sending a plurality of first-circuit-evaluations to the at least one or more classically-executable-nodes for processing.

18 . The method of claim 13 , further comprising:

storing the plurality of quantum-circuits in a circuit-buffer of the quantum computer;

selecting a quantum-circuit, of the plurality of quantum-circuits, based on a selection-policy;

evaluating the selected quantum-circuit to determine a selected-quantum-circuit-evaluation; and

sending the selected-quantum-circuit-evaluation to the at least one or more classically-executable-nodes for processing.

19 . The method of claim 18 , wherein the selection-policy comprises:

partitioning the plurality of quantum-circuits based on identifying, for each respective circuit of a respective partition, a common originating node of the one or more classically-executable-nodes;

determining a number of circuits present in each respective partition; and

determining that the quantum-circuit belongs to a partition with a smallest number of circuits.

20 . A computing system for executing a classical-quantum hybrid algorithm, the computing system comprising:

a classical computer comprising one or more classically-executable-nodes of the classical-quantum hybrid algorithm; and

a quantum computer comprising a quantum-processor-unit, wherein the quantum computer is operatively coupled to the classical computer;

wherein:

the one or more classically-executable-nodes are configured to send a first-circuit and a second-circuit to the quantum computer for evaluation;

the quantum computer is configured to:

receive the first-circuit and the second-circuit;

evaluate the first-circuit, using the quantum-processor-unit, to determine a first-circuit-evaluation; and

send the first-circuit-evaluation to the classical computer;

the one or more classically-executable-nodes are configured to:

receive the first-circuit-evaluation; and

process the first-circuit-evaluation during a first-time-interval;

the quantum computer is configured to:

evaluate, using the quantum-processor-unit, the second-circuit to determine a second-circuit-evaluation at least in part during the first-time-interval; and

send the second-circuit-evaluation to the classical computer.