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283 | class BosonicQubit(metaclass=ABCMeta):
"""
Base class for Bosonic Qubits.
"""
@property
def _non_device_params(self):
"""
Can be overriden in child classes.
"""
return ["N"]
def __init__(self, params: Optional[Dict[str, float]] = None, name: str = "bqubit"):
self.name = name
self.params = params if params else {}
self._params_validation()
self.params = device_put_params(self.params, self._non_device_params)
self.common_gates: Dict[str, jqt.Qarray] = {}
self._gen_common_gates()
self.wigner_pts = jnp.linspace(-4.5, 4.5, 61)
self.basis = self._get_basis_states()
for basis_state in ["+x", "-x", "+y", "-y", "+z", "-z"]:
assert (
basis_state in self.basis
), f"Please set the {basis_state} basis state."
def _params_validation(self):
"""
Override this method to add additional validation to params.
E.g.
if "N" not in self.params:
self.params["N"] = 50
"""
if "N" not in self.params:
self.params["N"] = 50
def _gen_common_gates(self):
"""
Override this method to add additional common gates.
E.g.
if "N" not in self.params:
self.params["N"] = 50
"""
N = self.params["N"]
self.common_gates["a_dag"] = jqt.create(N)
self.common_gates["a"] = jqt.destroy(N)
@abstractmethod
def _get_basis_z(self) -> Tuple[jqt.Qarray, jqt.Qarray]:
"""
Returns:
plus_z (jqt.Qarray), minus_z (jqt.Qarray): z basis states
"""
def _get_basis_states(self) -> Dict[str, jqt.Qarray]:
"""
Construct basis states |+-x>, |+-y>, |+-z>
"""
plus_z, minus_z = self._get_basis_z()
return self._gen_basis_states_from_z(plus_z, minus_z)
def _gen_basis_states_from_z(
self, plus_z: jqt.Qarray, minus_z: jqt.Qarray
) -> Dict[str, jqt.Qarray]:
"""
Construct basis states |+-x>, |+-y>, |+-z> from |+-z>
"""
basis: Dict[str, jqt.Qarray] = {}
N = self.params["N"]
# import to make sure that each basis state is a column vec
# otherwise, transposing a 1D vector will do nothing
basis["+z"] = plus_z
basis["-z"] = minus_z
basis["+x"] = jqt.unit(basis["+z"] + basis["-z"])
basis["-x"] = jqt.unit(basis["+z"] - basis["-z"])
basis["+y"] = jqt.unit(basis["+z"] + 1j * basis["-z"])
basis["-y"] = jqt.unit(basis["+z"] - 1j * basis["-z"])
return basis
def jqt2qt(self, state):
return jqt.jqt2qt(state)
# gates
# ======================================================
# @abstractmethod
# def stabilize(self) -> None:
# """
# Stabilizing/measuring syndromes.
# """
@property
def x_U(self) -> jqt.Qarray:
"""
Logical X unitary gate.
"""
return self._gen_pauli_U("x")
@property
def x_H(self) -> Optional[jqt.Qarray]:
"""
Logical X hamiltonian.
"""
return None
@property
def y_U(self) -> jqt.Qarray:
"""
Logical Y unitary gate.
"""
return self._gen_pauli_U("y")
@property
def y_H(self) -> Optional[jqt.Qarray]:
"""
Logical Y hamiltonian.
"""
return None
@property
def z_U(self) -> jqt.Qarray:
"""
Logical Z unitary gate.
"""
return self._gen_pauli_U("z")
@property
def z_H(self) -> Optional[jqt.Qarray]:
"""
Logical Z hamiltonian.
"""
return None
def _gen_pauli_U(self, basis_state: str) -> jqt.Qarray:
"""
Generates unitary for Pauli X, Y, Z.
Args:
basis_state (str): "x", "y", "z"
Returns:
U (jqt.Qarray): Pauli unitary
"""
H = getattr(self, basis_state + "_H")
if H is not None:
return jqt.expm(1.0j * H)
gate = (
self.basis["+" + basis_state] @ self.basis["+" + basis_state].dag()
- self.basis["-" + basis_state] @ self.basis["-" + basis_state].dag()
)
return gate
@property
def projector(self):
return (
self.basis["+z"] @ self.basis["+z"].dag()
+ self.basis["-z"] @ self.basis["-z"].dag()
)
@property
def maximally_mixed_state(self):
return (1 / 2.0) * self.projector()
# Plotting
# ======================================================
def _prepare_state_plot(self, state):
"""
Can be overriden.
E.g. in the case of cavity x transmon system
return qt.ptrace(state, 0)
"""
return state
def plot(self, state, ax=None, qp_type=jqt.WIGNER, **kwargs) -> None:
if ax is None:
fig, ax = plt.subplots(1, figsize=(4, 3), dpi=200)
fig = ax.get_figure()
if qp_type == jqt.WIGNER:
vmin = -1
vmax = 1
elif qp_type == jqt.QFUNC:
vmin = 0
vmax = 1
w_plt = self._plot_single(state, ax=ax, qp_type=qp_type, **kwargs)
ax.set_title(qp_type.capitalize() + " Quasi-Probability Dist.")
ticks = np.linspace(vmin, vmax, 5)
fig.colorbar(w_plt, ax=ax, ticks=ticks)
ax.set_xlabel(r"Re$(\alpha)$")
ax.set_ylabel(r"Im$(\alpha)$")
fig.tight_layout()
plt.show()
def _plot_single(self, state, ax=None, contour=True, qp_type=jqt.WIGNER):
"""
Assumes state has same dims as initial_state.
"""
state = self.jqt2qt(state)
if ax is None:
_, ax = plt.subplots(1, figsize=(4, 3), dpi=200)
return jqt.plot_qp(
state, self.wigner_pts, ax=ax, contour=contour, qp_type=qp_type
)
def plot_code_states(self, qp_type: str = jqt.WIGNER, **kwargs):
"""
Plot |±x⟩, |±y⟩, |±z⟩ code states.
Args:
qp_type (str):
WIGNER or QFUNC
Return:
axs: Axes
"""
fig, axs = plt.subplots(2, 3, figsize=(9, 6), dpi=200)
if qp_type == jqt.WIGNER:
cbar_title = r"$\frac{\pi}{2} W(\alpha)$"
vmin = -1
vmax = 1
elif qp_type == jqt.QFUNC:
cbar_title = r"$\pi Q(\alpha)$"
vmin = 0
vmax = 1
for i, label in enumerate(["+z", "+x", "+y", "-z", "-x", "-y"]):
state = self._prepare_state_plot(self.basis[label])
pos = (i // 3, i % 3)
ax = axs[pos]
w_plt = self._plot_single(state, ax=ax, qp_type=qp_type, **kwargs)
ax.set_title(f"|{label}" + r"$\rangle$")
ax.set_xlabel(r"Re[$\alpha$]")
ax.set_ylabel(r"Im[$\alpha$]")
fig.suptitle(self.name)
fig.tight_layout()
fig.subplots_adjust(right=0.8, hspace=0.2, wspace=0.2)
fig.align_xlabels(axs)
fig.align_ylabels(axs)
cbar_ax = fig.add_axes([0.85 + 0.2, 0.15, 0.05, 0.7])
ticks = np.linspace(vmin, vmax, 5)
fig.colorbar(w_plt, cax=cbar_ax, ticks=ticks)
cbar_ax.set_title(cbar_title, pad=20)
fig.tight_layout()
plt.show()
|