examples

PyQASM Usage Examples

Program Unrolling

from pyqasm import loads, dumps

qasm = """
OPENQASM 3;
include "stdgates.inc";

gate hgate q { h q; }
gate xgate q { x q; }

const int[32] N = 4;
qubit[4] q;
qubit ancilla;

def deutsch_jozsa(qubit[N] q_func, qubit[1] ancilla_q) {
  xgate ancilla_q;
  for int i in [0:N-1] { hgate q_func[i]; }
  hgate ancilla_q;
  for int i in [0:N-1] { cx q_func[i], ancilla_q; }
  for int i in [0:N-1] { hgate q_func[i]; }
}

deutsch_jozsa(q, ancilla);

bit[4] result;
result = measure q;
"""

module = loads(qasm)
module.unroll()
print(dumps(module))

OPENQASM 3;
include "stdgates.inc";
qubit[4] q;
qubit[1] ancilla;
x ancilla[0];
h q[0];
h q[1];
h q[2];
h q[3];
h ancilla[0];
cx q[0], ancilla[0];
cx q[1], ancilla[0];
cx q[2], ancilla[0];
cx q[3], ancilla[0];
h q[0];
h q[1];
h q[2];
h q[3];
bit[4] result;
result[0] = measure q[0];
result[1] = measure q[1];
result[2] = measure q[2];
result[3] = measure q[3];

pyqasm.QasmModule.unroll() simplifies a quantum program by expanding custom gate definitions and flattening complex constructs like subroutines, loops, and conditionals into basic operations. This process, also called program flattening or inlining, transforms the program into a linear sequence of qubit and classical bit declarations, gate operations, and measurements, making it easier to transpile or compile for execution on a quantum device. See the extended Deutsch Josza program unrolling example for more details about the OpenQASM 3 language features being "unrolled" in the above program.

Program Validation

from pyqasm import loads

program = """
OPENQASM 3;
include "stdgates.inc";

qubit[1] q;
bit[1] c;

// bad code
h q[2];

c = measure q;
"""

module = loads(program)

module.validate()

pyqasm.exceptions.ValidationError: Index 2 out of range for register of size 1 in qubit

pyqasm.QasmModule.validate() returns None if the program is semantically valid, otherwise raises an Exception. Check out a more detailed validation example for a deeper look into the capabilities of our semantic analyzer.