Classical algorithms are effective for optimization with low variable counts but struggle with larger problems due to combinatorial explosion.Quantum computing, utilizing superposition and entanglement, offers a parallel approach for large problems like QUBO.QAOA, a popular quantum algorithm for QUBO, requires 1 qubit per binary variable making it resource-intensive for large-scale problems.Qubit-efficient methods like PGE, ABE, and ACE offer alternatives suitable for NISQ devices and combinatorial optimization.These methods use fewer qubits and are scalable even on near-term quantum hardware.An image segmentation example is used to demonstrate the qubit-efficient techniques discussed.PGE encodes binary segmentation masks in rotation parameters of a diagonal gate requiring fewer qubits.The process involves quantum circuit initialization, encoding binary values, and cost function evaluation.A classic optimizer is used to optimize the result, mapping parameters to bits based on a threshold.The article references various quantum papers detailing the qubit-efficient encoding schemes used.