On September 29, a team led by academician Min Gu at the University of Shanghai for Science and Technology published its work on a new optical memory in the journal Nature Photonics. Each 3D recording point in this memory can take one of 1,024 possible states, which means it stores 10 bits.
In conventional binary memory, a cell has only two states, “0” or “1”, so it holds a single bit. The Shanghai design packs into one point what used to be spread across several cells. That means optical storage capacity no longer has to grow only by shrinking the points or stacking more layers.
For a DVD-sized disc, the researchers put the theoretical capacity at 0.4 petabits, or roughly 50TB. ITHome notes that read reliability exceeds 99.99%. Data is written at high speed and read in parallel across a wide area at once.
The team illustrates the value of the extra bits with an 8K grayscale image. Each pixel can take one of 256 brightness levels, so binary memory needs eight cells to store it. A 10-bit point holds those eight bits in full, and the remaining two can be used for optical AI training directly on the medium.
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Another difference lies in the optics themselves. Conventional super-dense optical recording relies on two beams that must be precisely aligned and stabilized. The Shanghai team writes and reads data with a single monochromatic beam, doing away with the complex dual-beam setup.
The researchers believe the technology has far more headroom. If the spacing between layers shrinks from 5 to 1 micrometer and the number of distinguishable states grows to tens of thousands, a DVD-sized disc could reach a theoretical 20 petabits, or about 2.5PB. Still, Gu stressed that capacity in petabits isn’t the only yardstick. To reach real-world use, the technology also has to balance read and write speeds, system complexity, and how easily it can be built into hardware.
Other teams are pushing memory forward in different ways. Earlier in September, another group of Chinese researchers created a material that lets memory withstand 10 billion rewrites.
