D-Wave has published a number of papers that show evidence of quantum effects such as superposition, quantum tunneling, and entanglement.
Entanglement in a Quantum Annealing Processor, by Lanting et al.
Quantum Annealing with Manufactured Spins, by Johnson et al.
Experimental Demonstration of a Robust and Scalable Flux Qubit, by Harris et al.
Access all D-Wave scientific publications (more than 100!) here.