  For any symmetric key cryptosystem with $n$-bit secret key, the key can be
recovered in $O(2^{n/2})$ exploiting Grover search algorithm, resulting in the
effective key length to be half. In this direction, subsequent work has been
done on AES and some other block ciphers. On the other hand, lightweight
ciphers like SIMON was left unexplored. In this backdrop, we present Grover's
search algorithm on all the variants of SIMON and enumerate the quantum
resources to implement such attack in terms of NOT, CNOT and Toffoli gates. We
also provide the T-depth of the circuits and the number of qubits required for
the attack. We show that the number of qubits required for implementing Grover
on SIMON $2n/mn$ is $O(2nr+mn)$, where $r$ is the number of chosen
plaintext-cipher text pairs. We run a reduced version of SIMON in IBMQ quantum
simulator and the 14-qubits processor as well. We found that where simulation
supports theory, the actual implementation is far from the reality due to the
infidelity of the gates and short decoherence time of the qubits. The complete
codes for all version of SIMON have also been presented.
