The mural that couldn’t stay linked
Before sunrise, a crew works a huge tiled mural. Every minute, two painters swap colours between neighbouring tiles, trying to build long repeating bands across the whole wall. Then an inspector seals a tile so it can’t change, and a cleaner wipes another back to plain white.
That wall is a stand-in for a quantum system. The long colour bands are the shared link people want to keep across far-apart parts. The inspector’s seal is like checking a tile and locking in an answer. The cleaner’s wipe is like random mess that quietly resets a spot to default.
Instead of tracking every swap, the crew tracks one thing: the border between the patterned tiles and the white tiles. They sketch that border each minute, then stack the sketches into a thick flipbook. Takeaway: the big question about shared links turns into a simpler one about which border paths are likely.
From that border view, a surprise drops. If wiping happens steadily across the whole wall, even a tiny bit, the mural can’t keep a wall-wide linked pattern for long. White patches keep appearing in the stacked history, tugging the border back towards white until the full-wall weave is gone.
Wipes are usually scattered, so they set a typical gap between white patches. The inspector’s seals don’t just shrink the border; they make it wander and get jagged, like a rough shoreline. After the dull bulk cancels out, the leftover link mostly comes from that jaggedness, following a simple power rule.
Then the rules change: the cleaner is only allowed to wipe along the outer frame. On a bigger wall, the frame is a smaller share of the whole. Now the border can roam across most of the mural before getting forced back, so the link grows slowly with wall size instead of flattening out.
The crew tests it. They hide a tiny signature mark on one tile, and keep a matching reference safe off the wall. After the swapping, sealing, and wiping have run for a while, they attach the signature and see how long the wall can still prove it matches the reference. Different wiping patterns change that time in different power-law ways.
By the end, the wall teaches a blunt lesson. A little steady wiping doesn’t just fade the picture; it changes what kind of long-distance linking can exist at all. The border flipbook makes the fight feel less like guesswork: swapping builds, sealing locks, wiping resets, and the border tells you what survives.