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Save mid-circuit measurement #256

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merged 10 commits into from
Jan 5, 2023
Merged

Save mid-circuit measurement #256

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18c56bf
Ported translate modules
KrzysztofB-1qbit Nov 22, 2022
54d32ed
Added the measurement saving functionality
KrzysztofB-1qbit Nov 25, 2022
3914752
commit modified file adapt.ipynb
KrzysztofB-1qbit Nov 25, 2022
4e29836
Corrected tests
KrzysztofB-1qbit Nov 25, 2022
c4d7734
Fixes after first review
KrzysztofB-1qbit Nov 29, 2022
e872d06
Changed Backend.marginal_frequencies -> post_selection.split_frequenc…
KrzysztofB-1qbit Nov 30, 2022
788fb5a
Moved split_frequency_dict call to Backend, fixes to target_cirq
KrzysztofB-1qbit Dec 5, 2022
1e5efb0
Docstring fixes
KrzysztofB-1qbit Dec 6, 2022
aeeff26
Docstrings and comments
KrzysztofB-1qbit Dec 16, 2022
cd5059b
Fixed undocumented function and left a todo for circular import
Jan 5, 2023
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12 changes: 6 additions & 6 deletions examples/adapt.ipynb
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101 changes: 64 additions & 37 deletions tangelo/linq/target/backend.py
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Original file line number Diff line number Diff line change
Expand Up @@ -48,9 +48,9 @@ def get_expectation_value_from_frequencies_oneterm(term, frequencies):
the result of a state-preparation.

Args:
term(openfermion-style QubitOperator object): a qubit operator, with
term (openfermion-style QubitOperator object): a qubit operator, with
only a single term.
frequencies(dict): histogram of frequencies of measurements (assumed
frequencies (dict): histogram of frequencies of measurements (assumed
to be in lsq-first format).

Returns:
Expand Down Expand Up @@ -82,9 +82,9 @@ def get_variance_from_frequencies_oneterm(term, frequencies):
"""Return the variance of the expectation value of a single-term qubit-operator, given
the result of a state-preparation.
Args:
term(openfermion-style QubitOperator object): a qubit operator, with
term (openfermion-style QubitOperator object): a qubit operator, with
only a single term.
frequencies(dict): histogram of frequencies of measurements (assumed
frequencies (dict): histogram of frequencies of measurements (assumed
to be in lsq-first format).
Returns:
complex: The variance of this operator with regard to the
Expand Down Expand Up @@ -153,12 +153,19 @@ def simulate_circuit(self):
equivalent gates.

Args:
source_circuit: a circuit in the abstract format to be translated
source_circuit (Circuit): a circuit in the abstract format to be translated
for the target backend.
return_statevector(bool): option to return the statevector as well,
return_statevector (bool): option to return the statevector as well,
if available.
initial_statevector(list/array) : A valid statevector in the format
initial_statevector (list/array) : A valid statevector in the format
supported by the target backend.
save_mid_circuit_meas (bool): Save mid-circuit measurement results to
self.mid_circuit_meas_freqs. All measurements will be saved to
self.all_frequencies, with keys of length (n_meas + n_qubits).
The leading n_meas values will hold the results of the MEASURE gates,
ordered by their appearance in the source_circuit.
The last n_qubits values will hold the measurements performed on
each of qubits at the end of the circuit.

Returns:
dict: A dictionary mapping multi-qubit states to their corresponding
Expand All @@ -168,7 +175,7 @@ def simulate_circuit(self):
"""
pass

def simulate(self, source_circuit, return_statevector=False, initial_statevector=None):
def simulate(self, source_circuit, return_statevector=False, initial_statevector=None, save_mid_circuit_meas=False):
"""Perform state preparation corresponding to the input circuit on the
target backend, return the frequencies of the different observables, and
either the statevector or None depending on the availability of the
Expand All @@ -178,20 +185,26 @@ def simulate(self, source_circuit, return_statevector=False, initial_statevector
equivalent gates.

Args:
source_circuit: a circuit in the abstract format to be translated
source_circuit (Circuit): a circuit in the abstract format to be translated
for the target backend.
return_statevector(bool): option to return the statevector as well,
return_statevector (bool): option to return the statevector as well,
if available.
initial_statevector(list/array) : A valid statevector in the format
initial_statevector (list/array) : A valid statevector in the format
supported by the target backend.
save_mid_circuit_meas (bool): Save mid-circuit measurement results to
self.mid_circuit_meas_freqs. All measurements will be saved to
self.all_frequencies, with keys of length (n_meas + n_qubits).
The leading n_meas values will hold the results of the MEASURE gates,
ordered by their appearance in the source_circuit.
The last n_qubits values will hold the measurements performed on
each of qubits at the end of the circuit.

Returns:
dict: A dictionary mapping multi-qubit states to their corresponding
frequency.
numpy.array: The statevector, if available for the target backend
and requested by the user (if not, set to None).
"""

if source_circuit.is_mixed_state and not self.n_shots:
raise ValueError("Circuit contains MEASURE instruction, and is assumed to prepare a mixed state."
"Please set the n_shots attribute to an appropriate value.")
Expand All @@ -211,7 +224,22 @@ def simulate(self, source_circuit, return_statevector=False, initial_statevector
statevector[0] = 1.0
return (frequencies, statevector) if return_statevector else (frequencies, None)

return self.simulate_circuit(source_circuit, return_statevector=return_statevector, initial_statevector=initial_statevector)
if save_mid_circuit_meas:
# TODO: refactor to break a circular import. May involve by relocating get_xxx_oneterm functions
from tangelo.toolboxes.post_processing.post_selection import split_frequency_dict
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(all_frequencies, statevector) = self.simulate_circuit(source_circuit,
return_statevector=return_statevector,
initial_statevector=initial_statevector,
save_mid_circuit_meas=save_mid_circuit_meas)
n_meas = source_circuit.counts.get("MEASURE", 0)
self.mid_circuit_meas_freqs, frequencies = split_frequency_dict(all_frequencies, list(range(n_meas)))
return (frequencies, statevector)

return self.simulate_circuit(source_circuit,
return_statevector=return_statevector,
initial_statevector=initial_statevector,
save_mid_circuit_meas=save_mid_circuit_meas)

def get_expectation_value(self, qubit_operator, state_prep_circuit, initial_statevector=None):
r"""Take as input a qubit operator H and a quantum circuit preparing a
Expand All @@ -225,9 +253,10 @@ def get_expectation_value(self, qubit_operator, state_prep_circuit, initial_stat
actual QPU.

Args:
qubit_operator(openfermion-style QubitOperator class): a qubit
qubit_operator (openfermion-style QubitOperator class): a qubit
operator.
state_prep_circuit: an abstract circuit used for state preparation.
state_prep_circuit (Circuit): an abstract circuit used for state preparation.
initial_statevector (array): The initial statevector for the simulation

Returns:
complex: The expectation value of this operator with regards to the
Expand Down Expand Up @@ -277,10 +306,10 @@ def get_variance(self, qubit_operator, state_prep_circuit, initial_statevector=N
actual QPU.

Args:
qubit_operator(openfermion-style QubitOperator class): a qubit
qubit_operator (openfermion-style QubitOperator class): a qubit
operator.
state_prep_circuit: an abstract circuit used for state preparation.
initial_statevector(list/array) : A valid statevector in the format
state_prep_circuit (Circuit): an abstract circuit used for state preparation.
initial_statevector (list/array) : A valid statevector in the format
supported by the target backend.

Returns:
Expand Down Expand Up @@ -328,10 +357,10 @@ def get_standard_error(self, qubit_operator, state_prep_circuit, initial_stateve
actual QPU.

Args:
qubit_operator(openfermion-style QubitOperator class): a qubit
qubit_operator (openfermion-style QubitOperator class): a qubit
operator.
state_prep_circuit: an abstract circuit used for state preparation.
initial_statevector(list/array) : A valid statevector in the format
state_prep_circuit (Circuit): an abstract circuit used for state preparation.
initial_statevector (list/array): A valid statevector in the format
supported by the target backend.

Returns:
Expand All @@ -348,10 +377,9 @@ def _get_expectation_value_from_statevector(self, qubit_operator, state_prep_cir
this function directly, please call "get_expectation_value" instead.

Args:
qubit_operator(openfermion-style QubitOperator class): a qubit
operator.
state_prep_circuit: an abstract circuit used for state preparation
(only pure states).
qubit_operator (openfermion-style QubitOperator class): a qubit operator.
state_prep_circuit (Circuit): an abstract circuit used for state preparation (only pure states).
initial_statevector (array): The initial state of the system

Returns:
complex: The expectation value of this operator with regards to the
Expand Down Expand Up @@ -400,9 +428,9 @@ def _get_expectation_value_from_frequencies(self, qubit_operator, state_prep_cir
using the frequencies of observable states.

Args:
qubit_operator(openfermion-style QubitOperator class): a qubit
operator.
state_prep_circuit: an abstract circuit used for state preparation.
qubit_operator (openfermion-style QubitOperator class): a qubitoperator.
state_prep_circuit (Circuit): an abstract circuit used for state preparation.
initial_statevector (array): The initial state of the system

Returns:
complex: The expectation value of this operator with regard to the
Expand Down Expand Up @@ -442,10 +470,9 @@ def _get_variance_from_frequencies(self, qubit_operator, state_prep_circuit, ini
using the frequencies of observable states.

Args:
qubit_operator(openfermion-style QubitOperator class): a qubit
operator.
state_prep_circuit: an abstract circuit used for state preparation.
initial_statevector(list/array) : A valid statevector in the format
qubit_operator (openfermion-style QubitOperator class): a qubit operator.
state_prep_circuit (Circuit): an abstract circuit used for state preparation.
initial_statevector (list/array) : A valid statevector in the format
supported by the target backend.

Returns:
Expand Down Expand Up @@ -487,9 +514,9 @@ def get_expectation_value_from_frequencies_oneterm(term, frequencies):
the result of a state-preparation.

Args:
term(openfermion-style QubitOperator object): a qubit operator, with
term (openfermion-style QubitOperator object): a qubit operator, with
only a single term.
frequencies(dict): histogram of frequencies of measurements (assumed
frequencies (dict): histogram of frequencies of measurements (assumed
to be in lsq-first format).

Returns:
Expand All @@ -505,9 +532,9 @@ def get_variance_from_frequencies_oneterm(term, frequencies):
the result of a state-preparation.

Args:
term(openfermion-style QubitOperator object): a qubit operator, with
term (openfermion-style QubitOperator object): a qubit operator, with
only a single term.
frequencies(dict): histogram of frequencies of measurements (assumed
frequencies (dict): histogram of frequencies of measurements (assumed
to be in lsq-first format).

Returns:
Expand All @@ -525,7 +552,7 @@ def _statevector_to_frequencies(self, statevector):
state |0>.

Args:
statevector(list or ndarray(complex)): an iterable 1D data-structure
statevector (list or ndarray(complex)): an iterable 1D data-structure
containing the amplitudes.

Returns:
Expand Down
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