Output from sample should be ordered

[zohimchandani]

Required prerequisites

• Search the issue tracker to check if your feature has already been mentioned or rejected in other issues.

Describe the feature

@cudaq.kernel 
def psi(): 
    qubits = cudaq.qvector(3)
    
    h(qubits[0])
    h(qubits[1])
    h(qubits[2])
    

counts = cudaq.sample(psi)
print(counts)

{ 110:144 101:121 100:131 011:103 001:132 111:118 010:129 000:122 }

Can the output be ordered according to binary notation of quantum states ie:

0 = 000 = 22 * 0 + 21 * 0 + 2**0 * 0 = 0
1 = 001
2 = 010
3 = 011

etc

[sacpis]

For the above code, do we want the order of the sample output like this

{ 111:118 110:144 101:121 100:131 011:103 010:129 001:132 000:122 }

or

{ 000:122 001:132 010:129 011:103 100:131 101:121 110:144 111:118 }?

[ikkoham]

Sorting of exponential sized data is costly and is not recommended to be sorted all the time.
It may be optional, but can be easily implemented as follows

import cudaq

@cudaq.kernel 
def psi(): 
    qubits = cudaq.qvector(3)
    
    h(qubits[0])
    h(qubits[1])
    h(qubits[2])

counts = cudaq.sample(psi)
sorted_counts = sorted(counts.items(), key=lambda x:x[0])
print(sorted_counts)

[('000', 131), ('001', 129), ('010', 105), ('011', 139), ('100', 139), ('101', 107), ('110', 131), ('111', 119)]

or

import cudaq

@cudaq.kernel 
def psi(): 
    qubits = cudaq.qvector(3)
    
    h(qubits[0])
    h(qubits[1])
    h(qubits[2])

counts = cudaq.sample(psi)
sorted_counts = sorted(counts.items(), key=lambda x:x[0][::-1])
print(sorted_counts)

[('000', 140), ('100', 123), ('010', 114), ('110', 119), ('001', 135), ('101', 137), ('011', 117), ('111', 115)]