Methods and systems for performing automatic gate-cutting of quantum circuits

A computer program which, when run on a hybrid quantum-classical computer, causes the computer to carry out a method of performing automatic gate-cutting of a target quantum circuit into a set of output subcircuits, comprising:

• identifying a target quantum circuit comprising a number of qubits and entanglement gates;
• identifying a subcircuit constraint defining the maximum number of qubits available per output subcircuit of the set of output subcircuits;
• performing a cutting algorithm to determine a set of optimum subcircuits, the cutting optimisation algorithm comprising:
• iteratively evaluating a cost function which determines candidate sets of subcircuits based on an assessment of the entanglement gates of the target quantum circuit, comprising determining for each candidate set of subcircuits:
• whether the subcircuit constraint is satisfied;
• and
• a subset of the entanglement gates to be cut to achieve the candidate set of subcircuits;
• minimising the cost function and defining the set of optimum subcircuits as the respective candidate set of subcircuits for which the cost function is minimised;
• and
• creating the set of output subcircuits, comprising cutting each of the entanglement gates of the respective subset of the entanglement gates to be cut to achieve the set of optimum subcircuits.

An information processing apparatus comprising a memory and a processor connected to the memory, wherein the processor is configured to perform the method of performing automatic gate-cutting of a target quantum circuit into a set of output subcircuits, comprising:

• identifying a target quantum circuit comprising a number of qubits and entanglement gates;
• identifying a subcircuit constraint defining the maximum number of qubits available per output subcircuit of the set of output subcircuits;
• performing a cutting algorithm to determine a set of optimum subcircuits, the cutting optimisation algorithm comprising:
• iteratively evaluating a cost function which determines candidate sets of subcircuits based on an assessment of the entanglement gates of the target quantum circuit, comprising determining for each candidate set of subcircuits:
• whether the subcircuit constraint is satisfied;
• and
• a subset of the entanglement gates to be cut to achieve the candidate set of subcircuits;
• minimising the cost function and defining the set of optimum subcircuits as the respective candidate set of subcircuits for which the cost function is minimised;
• and
• creating the set of output subcircuits, comprising cutting each of the entanglement gates of the respective subset of the entanglement gates to be cut to achieve the set of optimum subcircuits.