Automatic quantum program optimization using adjoint-via-conjugation annotations

A computer-implemented method, comprising:

• receiving a high-level description of a quantum program to be implemented in a quantum-computing device;
• and
• compiling the high-level description of the quantum program into a lower-level program that is executable by a quantum-computing device,
• wherein the compiling includes:
• converting statements in the high-level description into one or more conditional-adjoint statements;
• and
• generating the lower-level program so that the quantum-computing device uses one or more idle qubits in response to one or more adjoint-via-conjugation annotations rather than one or more clean qubits.

A system, comprising:

• a quantum computing device;
• and
• a classical computing device in communication with the quantum computing device,
• the classical computing device being programmed to perform a method comprising:
• compiling the high-level description of the quantum program into a lower-level program that is executable by a quantum-computing device, wherein the compiling includes:
• recognizing one or more adjoint-via-conjugation annotations in the high-level description;
• and
• generating the lower-level program so that the quantum-computing device uses one or more idle qubits in response to the one or more adjoint-via-conjugation annotations.