quchip.control.signal

Signal-chain transforms for control equipment.

Transforms operate on a SignalMap keyed by (drive_label, drive_index) and are owned by ControlEquipment (not by individual drives). The equipment applies them in order, after drives produce their raw line signals and before the engine assembles the Hamiltonian.

Available transforms

• Delay — per-line time shift.

• Gain — per-line complex scaling (IQ imbalance, attenuation).

• Crosstalk — linear leakage from a source line onto a victim line, parameterized by amplitude beta, angle theta, and relative delay. This is the standard single-parameter crosstalk model used e.g. in Sheldon et al., PRA 93, 060302 (2016) for two-qubit gate calibration, and in Sarovar et al., Quantum 4, 321 (2020) for crosstalk characterization.

Examples

>>> from quchip import ChargeDrive, Crosstalk, Delay, Gain
>>> # Crosstalk between two already-constructed drives:
>>> # xt = Crosstalk(source=drive_a, victim=drive_b, beta=0.02, theta=0.1)

Classes

Crosstalk(source, victim, beta[, theta, delay])	Linear crosstalk from a source drive line onto a victim line.
Delay(line, delta_t)	Shift every signal on line in time by delta_t ns.
Gain(line, factor)	Scale every signal on line by a complex factor.
SignalTransform()	Abstract base for signal-map transforms, auto-registered for serialization.

class quchip.control.signal.SignalTransform

Bases: Registrable, ABC

Abstract base for signal-map transforms, auto-registered for serialization.

The type registry, the {"type": ...} to_dict() stamp, and the from_dict dispatch are owned by the shared Registrable mixin; the parameter-less default reconstruction (cls()) covers transforms that carry no persisted state, while payload-carrying transforms override to_dict() / from_dict().

abstractmethod apply(signals)

Return the transformed signal map.

Parameters:

signals (dict[tuple[str, int], SignalNode])

Return type:

dict[tuple[str, int], SignalNode]

referenced_lines()

Return control-line labels referenced by this transform.

Return type:

tuple[str, …]

without_line(line)

Return this transform without line, or None when it must be dropped.

Parameters:

line (str)

Return type:

SignalTransform | None

class quchip.control.signal.Delay(line, delta_t)

Bases: SignalTransform

Shift every signal on line in time by delta_t ns.

Parameters:

• line (str)

• delta_t (float)

line: str

delta_t: float

apply(signals)

Time-shift every signal on line by delta_t ns.

Parameters:

signals (dict[tuple[str, int], SignalNode])

Return type:

dict[tuple[str, int], SignalNode]

referenced_lines()

Return control-line labels referenced by this transform.

Return type:

tuple[str, …]

to_dict()

Serialize into a JSON-safe dictionary.

Return type:

dict[str, Any]

classmethod from_dict(d)

Reconstruct from to_dict() output.

On the registry root, dispatch to the concrete subclass named by data["type"] (forwarding *args / **kwargs). On a concrete subclass, defer to _from_dict_payload(). Concrete subclasses that carry payload override this method directly.

Parameters:

d (dict[str, Any])

Return type:

Delay

class quchip.control.signal.Gain(line, factor)

Bases: SignalTransform

Scale every signal on line by a complex factor.

Parameters:

• line (str)

• factor (complex)

line: str

factor: complex

apply(signals)

Scale every signal on line by the complex factor.

Parameters:

signals (dict[tuple[str, int], SignalNode])

Return type:

dict[tuple[str, int], SignalNode]

referenced_lines()

Return control-line labels referenced by this transform.

Return type:

tuple[str, …]

to_dict()

Serialize into a JSON-safe dictionary.

Return type:

dict[str, Any]

classmethod from_dict(d)

Reconstruct from to_dict() output.

On the registry root, dispatch to the concrete subclass named by data["type"] (forwarding *args / **kwargs). On a concrete subclass, defer to _from_dict_payload(). Concrete subclasses that carry payload override this method directly.

Parameters:

d (dict[str, Any])

Return type:

Gain

class quchip.control.signal.Crosstalk(source, victim, beta, theta=0.0, delay=0.0)

Bases: SignalTransform

Linear crosstalk from a source drive line onto a victim line.

For each scheduled operation on the source line, adds

\[\beta\, e^{i\theta}\, s_\mathrm{src}(t - \Delta t)\]

onto the victim line, where \(s_\mathrm{src}\) is the source’s raw line signal — the frame-agnostic, carrier-free envelope signal the signal chain operates on, before stage 2 attaches any carrier or RWA modulation. Fidelity to classical microwave crosstalk is preserved downstream instead: stage 2 builds the victim’s Hamiltonian term using the source drive’s own carrier frequency for the leaked entry, not the victim’s, so a leaked pulse still lands at the source’s frequency (Balewski et al., arXiv:2502.05362, Eq. (3); Sheldon et al., PRA 93, 060302 (2016); Sarovar et al., Quantum 4, 321 (2020)). The delay shifts the baseband envelope; the carrier-phase part of a physical path delay (\(2\pi f \tau\)) belongs in theta.

Parameters:

• source (str | BaseDrive) – Source drive or its label.

• victim (str | BaseDrive) – Victim drive or its label.

• beta (float) – Leakage amplitude (dimensionless).

• theta (float) – Phase shift applied to the leaked signal, radians.

• delay (float) – Time shift of the leaked signal relative to the source, ns.

source: str

victim: str

beta: float

theta: float = 0.0

delay: float = 0.0

apply(signals)

Add the phase-rotated, delayed source signal onto the victim line.

Parameters:

signals (dict[tuple[str, int], SignalNode])

Return type:

dict[tuple[str, int], SignalNode]

referenced_lines()

Return control-line labels referenced by this transform.

Return type:

tuple[str, …]

to_dict()

Serialize into a JSON-safe dictionary.

Return type:

dict[str, Any]

classmethod from_dict(d)

Reconstruct from to_dict() output.

On the registry root, dispatch to the concrete subclass named by data["type"] (forwarding *args / **kwargs). On a concrete subclass, defer to _from_dict_payload(). Concrete subclasses that carry payload override this method directly.

Parameters:

d (dict[str, Any])

Return type:

Crosstalk