QuasiDistribution
class QuasiDistribution(data, shots=None, stddev_upper_bound=None)
Bases: dict
A dictlike class for representing quasiprobabilities.
Builds a quasiprobability distribution object.
Parameters

data (dict) –
Input quasiprobability data. Where the keys represent a measured classical value and the value is a float for the quasiprobability of that result. The keys can be one of several formats:
 A hexadecimal string of the form
"0x4a"
 A bit string e.g.
'0b1011'
or"01011"
 An integer
 A hexadecimal string of the form

shots (int) – Number of shots the distribution was derived from.

stddev_upper_bound (float) – An upper bound for the standard deviation
Raises
 TypeError – If the input keys are not a string or int
 ValueError – If the string format of the keys is incorrect
Methods
binary_probabilities
QuasiDistribution.binary_probabilities(num_bits=None)
Build a quasiprobabilities dictionary with binary string keys
Parameters
num_bits (int) – number of bits in the binary bitstrings (leading zeros will be padded). If None, a default value will be used. If keys are given as integers or strings with binary or hex prefix, the default value will be derived from the largest key present. If keys are given as bitstrings without prefix, the default value will be derived from the largest key length.
Returns
A dictionary where the keys are binary strings in the format
"0110"
Return type
dict
clear
QuasiDistribution.clear() → None. Remove all items from D.
copy
QuasiDistribution.copy() → a shallow copy of D
fromkeys
QuasiDistribution.fromkeys(value=None, /)
Create a new dictionary with keys from iterable and values set to value.
get
QuasiDistribution.get(key, default=None, /)
Return the value for key if key is in the dictionary, else default.
hex_probabilities
QuasiDistribution.hex_probabilities()
Build a quasiprobabilities dictionary with hexadecimal string keys
Returns
A dictionary where the keys are hexadecimal strings in the
format "0x1a"
Return type
dict
items
QuasiDistribution.items() → a setlike object providing a view on D's items
keys
QuasiDistribution.keys() → a setlike object providing a view on D's keys
nearest_probability_distribution
QuasiDistribution.nearest_probability_distribution(return_distance=False)
Takes a quasiprobability distribution and maps it to the closest probability distribution as defined by the L2norm.
Parameters
return_distance (bool) – Return the L2 distance between distributions.
Returns
Nearest probability distribution. float: Euclidean (L2) distance of distributions.
Return type
Notes
Method from Smolin et al., Phys. Rev. Lett. 108, 070502 (2012).
pop
QuasiDistribution.pop(k[, d]) → v, remove specified key and return the corresponding value.
If key is not found, d is returned if given, otherwise KeyError is raised
popitem
QuasiDistribution.popitem()
Remove and return a (key, value) pair as a 2tuple.
Pairs are returned in LIFO (lastin, firstout) order. Raises KeyError if the dict is empty.
setdefault
QuasiDistribution.setdefault(key, default=None, /)
Insert key with a value of default if key is not in the dictionary.
Return the value for key if key is in the dictionary, else default.
update
QuasiDistribution.update([E, ]**F) → None. Update D from dict/iterable E and F.
If E is present and has a .keys() method, then does: for k in E: D[k] = E[k] If E is present and lacks a .keys() method, then does: for k, v in E: D[k] = v In either case, this is followed by: for k in F: D[k] = F[k]
values
QuasiDistribution.values() → an object providing a view on D's values
Attributes
stddev_upper_bound
Return an upper bound on standard deviation of expval estimator.