  This technical review examines the different methods and approaches have been
used to create microwave modes of quantum correlation. Specifically, we
consider the electro-opto-mechanical, optoelectronics, 4-coupled qubits, and
InP HEMT coupled with two external oscillator methods, and evaluate their
effectiveness for quantum applications. Since these systems are open quantum
systems, they interact with their own environment medium and thermal bath. To
ensure an accurate comparison, we analyzed all of the systems using the same
criteria. Thus, at first all systems are introduced briefly, then the total
Hamiltonian is theoretically derived, and finally, the system dynamics are
analogously analyzed using the Lindblad master equation. We then calculate the
quantum correlation between cavity modes, signal-to-noise ratio, and fidelity
for each system to evaluate their performance. The results show that the
strength and nature of the calculated quantities vary among the systems. An
interesting result is the emergence of mixing behavior in the quantum
correlation and signal-to-noise ratio for systems that use different cavities.
It also identified a significant similarity between the 4-coupled qubits and
InP HEMT coupled with external oscillators methods, where an avoided-level
crossing occurs in the quantum correlation. Additionally, the study results
reveal a high consistency between the signal-to-noise ratio and classical
discord.
