  We discuss the characteristics of special perfect entanglers and construct
single parameter two-qubit circuits which are locally equivalent to special
perfect entanglers. We present the results obtained from the implementation of
one of the circuits using cross-resonance interaction and discuss their
applications. First, we show that the ability of two-qubit gates to create
entangled states can be described using the chords present in the argand
diagram of squared eigenvalues of nonlocal part of two-qubit gates. We show
that the entangling power of a two-qubit gate is proportional to the mean
squared length of the chords. We deduce the entangling characteristics of
special perfect entanglers from the argand diagram associated with them. We
implement a special perfect entangler circuit using echoed cross-resonance gate
and pulse-level programming for nine different circuit parameters. For a
particular input state, we perform quantum state tomography and calculate state
fidelity and concurrence of the obtained output density matrices. We also
measure the average gate fidelity for B gate circuit. We construct two
universal two-qubit quantum circuits using the special perfect entangler
circuits. These universal circuits can be used to generate all two-qubit gates.
We show that (n-1) B gate circuits can be used to generate n-qubit GHZ and
perfect W states. We generate three-qubit perfect W state. Perfect W state
generated using pulse-level programming shows better fidelity than the state
generated using echoed cross-resonance gate.
