Quantum memory is proposed as an analogue to classical computer memory. And while Quantum Random Access Memory (QRAM) gets most of the attention, there are also proposals for Quantum Read-Only Memory (QROM). The difference between QRAM and QROM is fundamentally no different than the difference between their respective classical analogues: changeable versus not changeable. Therefore, QRAM is proposed to allow retrieval of stored quantum information, as well as the updating of stored information after quantum computation. QROM, on the other hand, is proposed to allow only retrieval of stored quantum information; the stored information cannot be updated. Quantum State Preparation is computationally expensive, especially when Amplitude Encoding is involved. The concern is therefore that the time it takes to prepare quantum states will diminish or even negate the computational advantage that algorithms are expected to provide. Preparing and storing quantum states ahead of time or storing in between multiple runs of an experiment or even storing it between different experiments will help. Memory is a major contributor to how fast your computer runs. https://quantumzeitgeist.com/quantum-memory-qram-what-is-it-and-why-do-we-need-it/