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"""
qasm.py - Functions to parse a set of qasm commands into a SymPy Circuit.
Examples taken from Chuang's page: https://web.archive.org/web/20220120121541/https://www.media.mit.edu/quanta/qasm2circ/
The code returns a circuit and an associated list of labels.
>>> from sympy.physics.quantum.qasm import Qasm
>>> q = Qasm('qubit q0', 'qubit q1', 'h q0', 'cnot q0,q1')
>>> q.get_circuit()
CNOT(1,0)*H(1)
>>> q = Qasm('qubit q0', 'qubit q1', 'cnot q0,q1', 'cnot q1,q0', 'cnot q0,q1')
>>> q.get_circuit()
CNOT(1,0)*CNOT(0,1)*CNOT(1,0)
"""
__all__ = [
'Qasm',
]
from math import prod
from sympy.physics.quantum.gate import H, CNOT, X, Z, CGate, CGateS, SWAP, S, T,CPHASE
from sympy.physics.quantum.circuitplot import Mz
def read_qasm(lines):
return Qasm(*lines.splitlines())
def read_qasm_file(filename):
return Qasm(*open(filename).readlines())
def flip_index(i, n):
"""Reorder qubit indices from largest to smallest.
>>> from sympy.physics.quantum.qasm import flip_index
>>> flip_index(0, 2)
1
>>> flip_index(1, 2)
0
"""
return n-i-1
def trim(line):
"""Remove everything following comment # characters in line.
>>> from sympy.physics.quantum.qasm import trim
>>> trim('nothing happens here')
'nothing happens here'
>>> trim('something #happens here')
'something '
"""
if '#' not in line:
return line
return line.split('#')[0]
def get_index(target, labels):
"""Get qubit labels from the rest of the line,and return indices
>>> from sympy.physics.quantum.qasm import get_index
>>> get_index('q0', ['q0', 'q1'])
1
>>> get_index('q1', ['q0', 'q1'])
0
"""
nq = len(labels)
return flip_index(labels.index(target), nq)
def get_indices(targets, labels):
return [get_index(t, labels) for t in targets]
def nonblank(args):
for line in args:
line = trim(line)
if line.isspace():
continue
yield line
return
def fullsplit(line):
words = line.split()
rest = ' '.join(words[1:])
return fixcommand(words[0]), [s.strip() for s in rest.split(',')]
def fixcommand(c):
"""Fix Qasm command names.
Remove all of forbidden characters from command c, and
replace 'def' with 'qdef'.
"""
forbidden_characters = ['-']
c = c.lower()
for char in forbidden_characters:
c = c.replace(char, '')
if c == 'def':
return 'qdef'
return c
def stripquotes(s):
"""Replace explicit quotes in a string.
>>> from sympy.physics.quantum.qasm import stripquotes
>>> stripquotes("'S'") == 'S'
True
>>> stripquotes('"S"') == 'S'
True
>>> stripquotes('S') == 'S'
True
"""
s = s.replace('"', '') # Remove second set of quotes?
s = s.replace("'", '')
return s
class Qasm:
"""Class to form objects from Qasm lines
>>> from sympy.physics.quantum.qasm import Qasm
>>> q = Qasm('qubit q0', 'qubit q1', 'h q0', 'cnot q0,q1')
>>> q.get_circuit()
CNOT(1,0)*H(1)
>>> q = Qasm('qubit q0', 'qubit q1', 'cnot q0,q1', 'cnot q1,q0', 'cnot q0,q1')
>>> q.get_circuit()
CNOT(1,0)*CNOT(0,1)*CNOT(1,0)
"""
def __init__(self, *args, **kwargs):
self.defs = {}
self.circuit = []
self.labels = []
self.inits = {}
self.add(*args)
self.kwargs = kwargs
def add(self, *lines):
for line in nonblank(lines):
command, rest = fullsplit(line)
if self.defs.get(command): #defs come first, since you can override built-in
function = self.defs.get(command)
indices = self.indices(rest)
if len(indices) == 1:
self.circuit.append(function(indices[0]))
else:
self.circuit.append(function(indices[:-1], indices[-1]))
elif hasattr(self, command):
function = getattr(self, command)
function(*rest)
else:
print("Function %s not defined. Skipping" % command)
def get_circuit(self):
return prod(reversed(self.circuit))
def get_labels(self):
return list(reversed(self.labels))
def plot(self):
from sympy.physics.quantum.circuitplot import CircuitPlot
circuit, labels = self.get_circuit(), self.get_labels()
CircuitPlot(circuit, len(labels), labels=labels, inits=self.inits)
def qubit(self, arg, init=None):
self.labels.append(arg)
if init: self.inits[arg] = init
def indices(self, args):
return get_indices(args, self.labels)
def index(self, arg):
return get_index(arg, self.labels)
def nop(self, *args):
pass
def x(self, arg):
self.circuit.append(X(self.index(arg)))
def z(self, arg):
self.circuit.append(Z(self.index(arg)))
def h(self, arg):
self.circuit.append(H(self.index(arg)))
def s(self, arg):
self.circuit.append(S(self.index(arg)))
def t(self, arg):
self.circuit.append(T(self.index(arg)))
def measure(self, arg):
self.circuit.append(Mz(self.index(arg)))
def cnot(self, a1, a2):
self.circuit.append(CNOT(*self.indices([a1, a2])))
def swap(self, a1, a2):
self.circuit.append(SWAP(*self.indices([a1, a2])))
def cphase(self, a1, a2):
self.circuit.append(CPHASE(*self.indices([a1, a2])))
def toffoli(self, a1, a2, a3):
i1, i2, i3 = self.indices([a1, a2, a3])
self.circuit.append(CGateS((i1, i2), X(i3)))
def cx(self, a1, a2):
fi, fj = self.indices([a1, a2])
self.circuit.append(CGate(fi, X(fj)))
def cz(self, a1, a2):
fi, fj = self.indices([a1, a2])
self.circuit.append(CGate(fi, Z(fj)))
def defbox(self, *args):
print("defbox not supported yet. Skipping: ", args)
def qdef(self, name, ncontrols, symbol):
from sympy.physics.quantum.circuitplot import CreateOneQubitGate, CreateCGate
ncontrols = int(ncontrols)
command = fixcommand(name)
symbol = stripquotes(symbol)
if ncontrols > 0:
self.defs[command] = CreateCGate(symbol)
else:
self.defs[command] = CreateOneQubitGate(symbol)
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