This mode of operation for a sampler will provide results
in the form of measurement outcomes. It will not provide
access to state vectors (even if the underlying
sampling mechanism is a simulator). This method will substitute
parameters in the param_resolver attributes for sympy.Symbols
used within the Circuit. This circuit will be executed a number
of times specified in the repetitions attribute, though some
simulated implementations may instead sample from the final
distribution rather than execute the circuit each time.
Args
program
The circuit to sample from.
param_resolver
Parameters to run with the program.
repetitions
The number of times to sample.
Returns
cirq.Result that contains all the measurements for a run.
Provides measurement outcomes as a cirq.Result object. This
interface will operate in a similar way to the run method
except for executing asynchronously.
In order to gain a speedup from using this method instead of other run
methods, the following conditions must be satisfied:
1. All circuits must measure the same set of qubits.
2. The number of circuit repetitions must be the same for all
circuits. That is, the `repetitions` argument must be an integer,
or else a list with identical values.
This allows for sweeping over different parameter values,
unlike the run method. The params argument will provide a
mapping from sympy.Symbols used within the circuit to a set of
values. Unlike the run method, which specifies a single
mapping from symbol to value, this method allows a "sweep" of
values. This allows a user to specify execution of a family of
related circuits efficiently.
Args
program
The circuit to sample from.
params
Parameters to run with the program.
repetitions
The number of times to sample.
Returns
Result list for this run; one for each possible parameter resolver.
run_sweep_async
run_sweep_async(
program, params, repetitions=1
)
Asynchronously samples from the given Circuit.
By default, this method invokes run_sweep synchronously and simply
exposes its result is an awaitable. Child classes that are capable of
true asynchronous sampling should override it to use other strategies.
Args
program
The circuit to sample from.
params
Parameters to run with the program.
repetitions
The number of times to sample.
Returns
Result list for this run; one for each possible parameter resolver.
Samples the given Circuit, producing a pandas data frame.
This interface will operate in a similar way to the run method
except that it returns a pandas data frame rather than a cirq.Result
object.
Args
program
The circuit to sample from.
repetitions
The number of times to sample the program, for each
parameter mapping.
params
Maps symbols to one or more values. This argument can be
a dictionary, a list of dictionaries, a cirq.Sweep, a list of
cirq.Sweep, etc. The program will be sampled repetition
times for each mapping. Defaults to a single empty mapping.
Returns
A pandas.DataFrame with a row for each sample, and a column for
each measurement key as well as a column for each symbolic
parameter. Measurement results are stored as a big endian integer
representation with one bit for each measured qubit in the key.
See cirq.big_endian_int_to_bits and similar functions for how
to convert this integer into bits.
There is an also index column containing the repetition number,
for each parameter assignment.
Raises
ValueError
If a supplied sweep is invalid.
Examples:
a, b, c = cirq.LineQubit.range(3)sampler = cirq.Simulator()circuit = cirq.Circuit(cirq.X(a), cirq.measure(a, key='out'))print(sampler.sample(circuit, repetitions=4)) out0 11 12 13 1
Calculates estimated expectation values from samples of a circuit.
Please see also cirq.work.observable_measurement.measure_observables
for more control over how to measure a suite of observables.
This method can be run on any device or simulator that supports circuit sampling. Compare
with simulate_expectation_values in simulator.py, which is limited to simulators
but provides exact results.
Args
program
The circuit which prepares a state from which we sample expectation values.
observables
A list of observables for which to calculate expectation values.
num_samples
The number of samples to take. Increasing this value increases the
statistical accuracy of the estimate.
params
Parameters to run with the program.
permit_terminal_measurements
If the provided circuit ends in a measurement, this
method will generate an error unless this is set to True. This is meant to
prevent measurements from ruining expectation value calculations.
Returns
A list of expectation-value lists. The outer index determines the sweep, and the inner
index determines the observable. For instance, results[1][3] would select the fourth
observable measured in the second sweep.
Raises
ValueError
If the number of samples was not positive, if empty observables were
supplied, or if the provided circuit has terminal measurements and
permit_terminal_measurements is true.