def __init__(self, x0, x1, a0, a1, a2, b0, b1, b2, nbits = 3):
qr_input = QuantumRegister(nbits, 'input')
num_result_qubits = nbits * 2
qr_result = QuantumRegister(num_result_qubits, 'result')
self.num_ancilla_qubits = 2 + num_result_qubits + 3
qr_ancilla = QuantumRegister(self.num_ancilla_qubits, 'ancilla')
qr_comp_anc = qr_ancilla[0:2]
qr_arith_anc = qr_ancilla[2:2 + num_result_qubits]
qr_range_anc = qr_ancilla[2 + num_result_qubits:2 + num_result_qubits + 3]
super().__init__(qr_input, qr_result, qr_ancilla, name='pwise_lin_trans')
comp0 = IntegerComparator(num_state_qubits=nbits, value=x0, name = "comparator0") # true if i >= point
comp1 = IntegerComparator(num_state_qubits=nbits, value=x1, name = "comparator1") # true if i >= point
trans0 = multiply_add.cond_classical_add_mult(a0, b0, qr_input, qr_result, qr_arith_anc)
trans1 = multiply_add.cond_classical_add_mult(a1, b1, qr_input, qr_result, qr_arith_anc)
trans2 = multiply_add.cond_classical_add_mult(a2, b2, qr_input, qr_result, qr_arith_anc)
self.append(comp0.to_gate(), qr_input[:] + [qr_comp_anc[0]] + qr_arith_anc[0:comp0.num_ancillas])
self.append(comp1.to_gate(), qr_input[:] + [qr_comp_anc[1]] + qr_arith_anc[0:comp1.num_ancillas])
# use three additional ancillas to define the ranges
self.cx(qr_comp_anc[0], qr_range_anc[0])
self.x(qr_range_anc[0])
self.cx(qr_comp_anc[1], qr_range_anc[2])
self.x(qr_range_anc[2])
self.ccx(qr_comp_anc[0], qr_range_anc[2], qr_range_anc[1])
self.append(trans0, [qr_range_anc[0]] + qr_input[:] + qr_result[:] + qr_arith_anc[:])
self.append(trans1, [qr_range_anc[1]] + qr_input[:] + qr_result[:] + qr_arith_anc[:])
self.append(trans2, [qr_comp_anc[1]] + qr_input[:] + qr_result[:] + qr_arith_anc[:])
# uncompute range ancillas
self.ccx(qr_comp_anc[0], qr_range_anc[2], qr_range_anc[1])
self.x(qr_range_anc[2])
self.cx(qr_comp_anc[1], qr_range_anc[2])
self.x(qr_range_anc[0])
self.cx(qr_comp_anc[0], qr_range_anc[0])
# uncompute comparator ancillas
self.append(comp1.to_gate().inverse(), qr_input[:] + [qr_comp_anc[1]] + qr_arith_anc[0:comp1.num_ancillas])
self.append(comp0.to_gate().inverse(), qr_input[:] + [qr_comp_anc[0]] + qr_arith_anc[0:comp0.num_ancillas])
def __init__(self, num_state_qubits: int, strike_price: float, bounds: Tuple[float, float]
) -> None:
"""
Args:
num_state_qubits: The number of qubits used to encode the random variable.
strike_price: strike price of the European option
bounds: The tuple of the bounds, (min, max), of the discretized random variable.
"""
# map strike price to {0, ..., 2^n-1}
num_values = 2 ** num_state_qubits
strike_price = (strike_price - bounds[0]) / (bounds[1] - bounds[0]) * (num_values - 1)
strike_price = int(np.ceil(strike_price))
# create comparator
comparator = IntegerComparator(num_state_qubits, strike_price)
# initialize circuit
qr_state = QuantumRegister(comparator.num_qubits - comparator.num_ancillas, 'state')
qr_work = QuantumRegister(comparator.num_ancillas, 'work')
super().__init__(qr_state, qr_work, name='ECD')
self.append(comparator.to_gate(), self.qubits)