qml.resource.SpectralNormError

class SpectralNormError(error)

Bases: pennylane.resource.error.error.AlgorithmicError

Class representing the spectral norm error.

The spectral norm error is defined as the distance, in spectral norm, between the true unitary we intend to apply and the approximate unitary that is actually applied.

Parameters

error (float) – The numerical value of the error

Example

>>> s1 = SpectralNormError(0.01)
>>> s2 = SpectralNormError(0.02)
>>> s1.combine(s2)
SpectralNormError(0.03)

Methods

combine(other)	Combine two spectral norm errors.
get_error(approximate_op, exact_op)	Compute spectral norm error between two operators.

combine(other)

Combine two spectral norm errors.

Parameters

other (SpectralNormError) – The other instance of error being combined.

Returns

The total error after combination.

Return type

SpectralNormError

Example

>>> s1 = SpectralNormError(0.01)
>>> s2 = SpectralNormError(0.02)
>>> s1.combine(s2)
SpectralNormError(0.03)

static get_error(approximate_op, exact_op)

Compute spectral norm error between two operators.

Parameters

• approximate_op (Operator) – The approximate operator.

• exact_op (Operator) – The exact operator.

Returns

The error between the exact operator and its approximation.

Return type

float

Example

>>> Op1 = qml.RY(0.40, 0)
>>> Op2 = qml.RY(0.41, 0)
>>> SpectralNormError.get_error(Op1, Op2)
0.004999994791668309

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