qiskit.providers.aer.noise.ReadoutError

class ReadoutError(probabilities, atol=1e-08)

Readout error class for Qiskit Aer noise model.

Create a readout error for a noise model.

For an N-qubit readout error probabilities are entered as vectors:

probabilities[m] = [P(0|m), P(1|m), ..., P(2 ** N - 1|m)]

where P(j|m) is the probability of recording a measurement outcome of m as the value j. Where j and m are integer representations of bit-strings.

Example: 1-qubit

probabilities[0] = [P("0"|"0"), P("1"|"0")]
probabilities[1] = [P("0"|"1"), P("1"|"1")]

Example: 2-qubit

probabilities[0] = [P("00"|"00"), P("01"|"00"), P("10"|"00"), P("11"|"00")]
probabilities[1] = [P("00"|"01"), P("01"|"01"), P("10"|"01"), P("11"|"01")]
probabilities[2] = [P("00"|"10"), P("01"|"10"), P("10"|"10"), P("11"|"10")]
probabilities[3] = [P("00"|"11"), P("01"|"11"), P("10"|"11"), P("11"|"11")]

Parameters

• probabilities (matrix) – List of outcome assignment probabilities.

• atol (double) – Threshold for checking probabilities are normalized (Default: 1e-8).

__init__(probabilities, atol=1e-08)

Create a readout error for a noise model.

For an N-qubit readout error probabilities are entered as vectors:

probabilities[m] = [P(0|m), P(1|m), ..., P(2 ** N - 1|m)]

where P(j|m) is the probability of recording a measurement outcome of m as the value j. Where j and m are integer representations of bit-strings.

Example: 1-qubit

probabilities[0] = [P("0"|"0"), P("1"|"0")]
probabilities[1] = [P("0"|"1"), P("1"|"1")]

Example: 2-qubit

probabilities[0] = [P("00"|"00"), P("01"|"00"), P("10"|"00"), P("11"|"00")]
probabilities[1] = [P("00"|"01"), P("01"|"01"), P("10"|"01"), P("11"|"01")]
probabilities[2] = [P("00"|"10"), P("01"|"10"), P("10"|"10"), P("11"|"10")]
probabilities[3] = [P("00"|"11"), P("01"|"11"), P("10"|"11"), P("11"|"11")]

Parameters

• probabilities (matrix) – List of outcome assignment probabilities.

• atol (double) – Threshold for checking probabilities are normalized (Default: 1e-8).

Methods

__init__(probabilities[, atol])	Create a readout error for a noise model.
compose(other[, front])	Return the composition readout error other * self.
copy()	Make a copy of current ReadoutError.
dot(other)	Return the composition readout error self * other.
expand(other)	Return the tensor product readout error self ⊗ other.
ideal()	Return True if current error object is an identity
power(n)	Return the compose of the readout error with itself n times.
set_atol(value)	Set the class default absolute tolerance parameter for float comparisons.
set_rtol(value)	Set the class default relative tolerance parameter for float comparisons.
tensor(other)	Return the tensor product readout error self ⊗ other.
to_dict()	Return the current error as a dictionary.
to_instruction()	Convert the ReadoutError to a circuit Instruction.

Attributes

atol	The default absolute tolerance parameter for float comparisons.
number_of_qubits	Return the number of qubits for the error.
probabilities	Return the readout error probabilities matrix.
rtol	The relative tolerance parameter for float comparisons.

property atol

The default absolute tolerance parameter for float comparisons.

compose(other, front=False)

Return the composition readout error other * self.

Note that for front=True this is equivalent to the ReadoutError.dot() method.

Parameters

• other (ReadoutError) – a readout error.

• front (bool) – If True return the reverse order composation self * other instead [default: False].

Returns

The composition readout error.

Return type

ReadoutError

Raises

• NoiseError – if other is not a ReadoutError or has incompatible

• dimensions. –

copy()

Make a copy of current ReadoutError.

dot(other)

Return the composition readout error self * other.

Parameters

other (ReadoutError) – a readout error.

Returns

The composition readout error.

Return type

ReadoutError

Raises

• NoiseError – if other is not a ReadoutError or has incompatible

• dimensions. –

expand(other)

Return the tensor product readout error self ⊗ other.

Parameters

other (ReadoutError) – a readout error.

Returns

the tensor product readout error other ⊗ self.

Return type

ReadoutError

Raises

NoiseError – if other is not a ReadoutError.

ideal()

Return True if current error object is an identity

property number_of_qubits

Return the number of qubits for the error.

power(n)

Return the compose of the readout error with itself n times.

Parameters

n (int) – the number of times to compose with self (n>0).

Returns

the n-times composition channel.

Return type

ReadoutError

Raises

NoiseError – if the power is not a positive integer.

property probabilities

Return the readout error probabilities matrix.

property rtol

The relative tolerance parameter for float comparisons.

classmethod set_atol(value)

Set the class default absolute tolerance parameter for float comparisons.

classmethod set_rtol(value)

Set the class default relative tolerance parameter for float comparisons.

tensor(other)

Return the tensor product readout error self ⊗ other.

Parameters

other (ReadoutError) – a readout error.

Returns

the tensor product readout error self ⊗ other.

Return type

ReadoutError

Raises

NoiseError – if other is not a ReadoutError.

to_dict()

Return the current error as a dictionary.

to_instruction()

Convert the ReadoutError to a circuit Instruction.