Yes, "have", not "is". You can, I think, speak of a quantum of energy or a quantum of spin or a quantum of momentum or a quantum of electric charge. Historically the term quantum theory arose in this way, because such properties of matter and fields were found often to be present in discrete chunks, rather than having a continuous range of values. So people like Schrödinger could quite reasonably speak of a quantum of energy. Today you can hear people talk of things like a photon "being" a quantum: in that case a quantum of light radiation. That too is correct, since it means light (which is "stuff", viz. electromagnetic radiation, viz. a system that can have energy) is not continuous but comes in little chunks, too. So when reading these things one needs to keep the context in mind and resist the temptation to quote-mine.