Source code for qutip.qip.models.spinchain

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import numpy as np
from qutip.operators import sigmax, sigmay, sigmaz, identity
from qutip.tensor import tensor
from qutip.qip.circuit import QubitCircuit
from qutip.qip.models.circuitprocessor import CircuitProcessor


[docs]class SpinChain(CircuitProcessor): """ Representation of the physical implementation of a quantum program/algorithm on a spin chain qubit system. """ def __init__(self, N, correct_global_phase=True, sx=None, sz=None, sxsy=None): """ Parameters ---------- sx: Integer/List The delta for each of the qubits in the system. sz: Integer/List The epsilon for each of the qubits in the system. sxsy: Integer/List The interaction strength for each of the qubit pair in the system. """ super(SpinChain, self).__init__(N, correct_global_phase) self.sx_ops = [tensor([sigmax() if m == n else identity(2) for n in range(N)]) for m in range(N)] self.sz_ops = [tensor([sigmaz() if m == n else identity(2) for n in range(N)]) for m in range(N)] self.sxsy_ops = [] for n in range(N - 1): x = [identity(2)] * N x[n] = x[n + 1] = sigmax() y = [identity(2)] * N y[n] = y[n + 1] = sigmay() self.sxsy_ops.append(tensor(x) + tensor(y)) if sx is None: self.sx_coeff = [0.25 * 2 * np.pi] * N elif not isinstance(sx, list): self.sx_coeff = [sx * 2 * np.pi] * N else: self.sx_coeff = sx if sz is None: self.sz_coeff = [1.0 * 2 * np.pi] * N elif not isinstance(sz, list): self.sz_coeff = [sz * 2 * np.pi] * N else: self.sz_coeff = sz if sxsy is None: self.sxsy_coeff = [0.1 * 2 * np.pi] * (N - 1) elif not isinstance(sxsy, list): self.sxsy_coeff = [sxsy * 2 * np.pi] * (N - 1) else: self.sxsy_coeff = sxsy def get_ops_and_u(self): return (self.sx_ops + self.sz_ops + self.sxsy_ops, np.hstack((self.sx_u, self.sz_u, self.sxsy_u))) def load_circuit(self, qc): gates = self.optimize_circuit(qc).gates self.global_phase = 0 self.sx_u = np.zeros((len(gates), len(self.sx_ops))) self.sz_u = np.zeros((len(gates), len(self.sz_ops))) self.sxsy_u = np.zeros((len(gates), len(self.sxsy_ops))) self.T_list = [] n = 0 for gate in gates: if gate.name == "ISWAP": g = self.sxsy_coeff[min(gate.targets)] if min(gate.targets) == 0 and max(gate.targets) == self.N - 1: self.sxsy_u[n, self.N - 1] = -g else: self.sxsy_u[n, min(gate.targets)] = -g T = np.pi / (4 * g) self.T_list.append(T) n += 1 elif gate.name == "SQRTISWAP": g = self.sxsy_coeff[min(gate.targets)] if min(gate.targets) == 0 and max(gate.targets) == self.N - 1: self.sxsy_u[n, self.N - 1] = -g else: self.sxsy_u[n, min(gate.targets)] = -g T = np.pi / (8 * g) self.T_list.append(T) n += 1 elif gate.name == "RZ": g = self.sz_coeff[gate.targets[0]] self.sz_u[n, gate.targets[0]] = np.sign(gate.arg_value) * g T = abs(gate.arg_value) / (2 * g) self.T_list.append(T) n += 1 elif gate.name == "RX": g = self.sx_coeff[gate.targets[0]] self.sx_u[n, gate.targets[0]] = np.sign(gate.arg_value) * g T = abs(gate.arg_value) / (2 * g) self.T_list.append(T) n += 1 elif gate.name == "GLOBALPHASE": self.global_phase += gate.arg_value else: raise ValueError("Unsupported gate %s" % gate.name)
[docs] def adjacent_gates(self, qc, setup="linear"): """ Method to resolve 2 qubit gates with non-adjacent control/s or target/s in terms of gates with adjacent interactions for linear/circular spin chain system. Parameters ---------- qc: QubitCircuit The circular spin chain circuit to be resolved setup: Boolean Linear of Circular spin chain setup Returns ---------- qc: QubitCircuit Returns QubitCircuit of resolved gates for the qubit circuit in the desired basis. """ qc_t = QubitCircuit(qc.N, qc.reverse_states) swap_gates = ["SWAP", "ISWAP", "SQRTISWAP", "SQRTSWAP", "BERKELEY", "SWAPalpha"] N = qc.N for gate in qc.gates: if gate.name == "CNOT" or gate.name == "CSIGN": start = min([gate.targets[0], gate.controls[0]]) end = max([gate.targets[0], gate.controls[0]]) if (setup == "linear" or (setup == "circular" and (end - start) <= N // 2)): i = start while i < end: if (start + end - i - i == 1 and (end - start + 1) % 2 == 0): # Apply required gate if control and target are # adjacent to each other, provided |control-target| # is even. if end == gate.controls[0]: qc_t.add_gate(gate.name, targets=[i], controls=[i + 1]) else: qc_t.add_gate(gate.name, targets=[i + 1], controls=[i]) elif (start + end - i - i == 2 and (end - start + 1) % 2 == 1): # Apply a swap between i and its adjacent gate, # then the required gate if and then another swap # if control and target have one qubit between # them, provided |control-target| is odd. qc_t.add_gate("SWAP", targets=[i, i + 1]) if end == gate.controls[0]: qc_t.add_gate(gate.name, targets=[i + 1], controls=[i + 2]) else: qc_t.add_gate(gate.name, targets=[i + 2], controls=[i + 1]) qc_t.add_gate("SWAP", [i, i + 1]) i += 1 else: # Swap the target/s and/or control with their # adjacent qubit to bring them closer. qc_t.add_gate("SWAP", [i, i + 1]) qc_t.add_gate("SWAP", [start + end - i - 1, start + end - i]) i += 1 elif (end - start) < N - 1: """ If the resolving has to go backwards, the path is first mapped to a separate circuit and then copied back to the original circuit. """ temp = QubitCircuit(N - end + start) i = 0 while i < (N - end + start): if (N + start - end - i - i == 1 and (N - end + start + 1) % 2 == 0): if end == gate.controls[0]: temp.add_gate(gate.name, targets=[i], controls=[i + 1]) else: temp.add_gate(gate.name, targets=[i + 1], controls=[i]) elif (N + start - end - i - i == 2 and (N - end + start + 1) % 2 == 1): temp.add_gate("SWAP", targets=[i, i + 1]) if end == gate.controls[0]: temp.add_gate(gate.name, targets=[i + 2], controls=[i + 1]) else: temp.add_gate(gate.name, targets=[i + 1], controls=[i + 2]) temp.add_gate("SWAP", [i, i + 1]) i += 1 else: temp.add_gate("SWAP", [i, i + 1]) temp.add_gate("SWAP", [N + start - end - i - 1, N + start - end - i]) i += 1 j = 0 for gate in temp.gates: if (j < N - end - 2): if gate.name in ["CNOT", "CSIGN"]: qc_t.add_gate(gate.name, end + gate.targets[0], end + gate.controls[0]) else: qc_t.add_gate(gate.name, [end + gate.targets[0], end + gate.targets[1]]) elif (j == N - end - 2): if gate.name in ["CNOT", "CSIGN"]: qc_t.add_gate(gate.name, end + gate.targets[0], (end + gate.controls[0]) % N) else: qc_t.add_gate(gate.name, [end + gate.targets[0], (end + gate.targets[1]) % N]) else: if gate.name in ["CNOT", "CSIGN"]: qc_t.add_gate(gate.name, (end + gate.targets[0]) % N, (end + gate.controls[0]) % N) else: qc_t.add_gate(gate.name, [(end + gate.targets[0]) % N, (end + gate.targets[1]) % N]) j = j + 1 elif (end - start) == N - 1: qc_t.add_gate(gate.name, gate.targets, gate.controls) elif gate.name in swap_gates: start = min([gate.targets[0], gate.targets[1]]) end = max([gate.targets[0], gate.targets[1]]) if (setup == "linear" or (setup == "circular" and (end - start) <= N // 2)): i = start while i < end: if (start + end - i - i == 1 and (end - start + 1) % 2 == 0): qc_t.add_gate(gate.name, [i, i + 1]) elif ((start + end - i - i) == 2 and (end - start + 1) % 2 == 1): qc_t.add_gate("SWAP", [i, i + 1]) qc_t.add_gate(gate.name, [i + 1, i + 2]) qc_t.add_gate("SWAP", [i, i + 1]) i += 1 else: qc_t.add_gate("SWAP", [i, i + 1]) qc_t.add_gate("SWAP", [start + end - i - 1, start + end - i]) i += 1 else: temp = QubitCircuit(N - end + start) i = 0 while i < (N - end + start): if (N + start - end - i - i == 1 and (N - end + start + 1) % 2 == 0): temp.add_gate(gate.name, [i, i + 1]) elif (N + start - end - i - i == 2 and (N - end + start + 1) % 2 == 1): temp.add_gate("SWAP", [i, i + 1]) temp.add_gate(gate.name, [i + 1, i + 2]) temp.add_gate("SWAP", [i, i + 1]) i += 1 else: temp.add_gate("SWAP", [i, i + 1]) temp.add_gate("SWAP", [N + start - end - i - 1, N + start - end - i]) i += 1 j = 0 for gate in temp.gates: if(j < N - end - 2): qc_t.add_gate(gate.name, [end + gate.targets[0], end + gate.targets[1]]) elif(j == N - end - 2): qc_t.add_gate(gate.name, [end + gate.targets[0], (end + gate.targets[1]) % N]) else: qc_t.add_gate(gate.name, [(end + gate.targets[0]) % N, (end + gate.targets[1]) % N]) j = j + 1 else: qc_t.add_gate(gate.name, gate.targets, gate.controls, gate.arg_value, gate.arg_label) return qc_t
[docs]class LinearSpinChain(SpinChain): """ Representation of the physical implementation of a quantum program/algorithm on a spin chain qubit system arranged in a linear formation. It is a sub-class of SpinChain. """ def __init__(self, N, correct_global_phase=True, sx=None, sz=None, sxsy=None): super(LinearSpinChain, self).__init__(N, correct_global_phase, sx, sz, sxsy) def get_ops_labels(self): return ([r"$\sigma_x^%d$" % n for n in range(self.N)] + [r"$\sigma_z^%d$" % n for n in range(self.N)] + [r"$\sigma_x^%d\sigma_x^{%d} + \sigma_y^%d\sigma_y^{%d}$" % (n, n, n + 1, n + 1) for n in range(self.N - 1)]) def optimize_circuit(self, qc): self.qc0 = qc self.qc1 = self.adjacent_gates(self.qc0, "linear") self.qc2 = self.qc1.resolve_gates(basis=["ISWAP", "RX", "RZ"]) return self.qc2
[docs]class CircularSpinChain(SpinChain): """ Representation of the physical implementation of a quantum program/algorithm on a spin chain qubit system arranged in a circular formation. It is a sub-class of SpinChain. """ def __init__(self, N, correct_global_phase=True, sx=None, sz=None, sxsy=None): super(CircularSpinChain, self).__init__(N, correct_global_phase, sx, sz, sxsy) x = [identity(2)] * N x[0] = x[N - 1] = sigmax() y = [identity(2)] * N y[0] = y[N - 1] = sigmay() self.sxsy_ops.append(tensor(x) + tensor(y)) if sxsy is None: self.sxsy_coeff = [0.1 * 2 * np.pi] * N elif not isinstance(sxsy, list): self.sxsy_coeff = [sxsy * 2 * np.pi] * N else: self.sxsy_coeff = sxsy def get_ops_labels(self): return ([r"$\sigma_x^%d$" % n for n in range(self.N)] + [r"$\sigma_z^%d$" % n for n in range(self.N)] + [r"$\sigma_x^%d\sigma_x^{%d} + \sigma_y^%d\sigma_y^{%d}$" % (n, n, (n + 1) % self.N, (n + 1) % self.N) for n in range(self.N)]) def optimize_circuit(self, qc): self.qc0 = qc self.qc1 = self.adjacent_gates(self.qc0, "circular") self.qc2 = self.qc1.resolve_gates(basis=["ISWAP", "RX", "RZ"]) return self.qc2