Extended Data Fig. 9: Concept of ultrafast ultra-scaled multilevel glass-like memory in VO₂.

a, Scheme of a four-level glass-like memory including three reference bits R₁, R₂, and R₃ (written by different number of pulses, N₁, N₂, and N₃, respectively) and n ordinary bit B_k. b, Reading process starts by processing the reference bits to extract the pulse width needed to trigger IMT in each reference bit. It is possible to apply a train of pulses with increasing widths until an IMT event takes place: this gives the incubation time corresponding to a VO₂ switch which is excited by N_k pulses. It is also possible to apply a longer pulse and measure the IMT time delay (incubation time). A pulse with width equal to the incubation time is able to fire IMT with those bits that are activated with the same number of pulses as the reference bit (N_k). We call this a key pulse. c, Three key pulses with pulse-widths W₁, W₂ and W₃ are obtained (W₁ < W₂ < W₃). d, Three key pulses are applied to each bit B_k to accomplish the reading process. e, Comparison between the glass-like memory and other technologies.