The symbol is derived from the first letters of the surnames of authors who wrote the first paper on wormholes (Albert Einstein and Nathan Rosen)[4] and the first paper on entanglement (Einstein, Boris Podolsky and Rosen).[5] The two papers were published in 1935, but the authors did not claim any connection between the concepts.[2]
Conjectured resolution
This is a conjectured resolution to the AMPS firewall paradox. Whether or not there is a firewall depends upon what is thrown into the other distant black hole. However, as the firewall lies inside the event horizon, no external superluminal signalling would be possible.
They backed up their conjecture by showing that the pair production of charged black holes in a background magnetic field leads to entangled black holes, but also, after Wick rotation, to a wormhole.
Susskind and Maldacena envisioned gathering up all the Hawking particles and smushing them together until they collapse into a black hole. That black hole would be entangled, and thus connected via wormhole, with the original black hole. That trick transformed a confusing mess of Hawking particles—paradoxically entangled with both a black hole and each other—into two black holes connected by a wormhole. Entanglement overload is averted, and the firewall problem goes away.
— Andrew Grant, "Entanglement: Gravity's long-distance connection", Science News[7]
This conjecture sits uncomfortably with the linearity of quantum mechanics. An entangled state is a linear superposition of separable states. Presumably, separable states are not connected by any wormholes, but yet a superposition of such states is connected by a wormhole.[8]
The authors pushed this conjecture even further by claiming any entangled pair of particles—even particles not ordinarily considered to be black holes, and pairs of particles with different masses or spin, or with charges which aren't opposite—are connected by Planck scale wormholes.
The conjecture leads to a grander conjecture that the geometry of space, time and gravity is determined by entanglement.[2][9][10]
^Sean M. Carroll (July 18, 2016). "Space Emerging from Quantum Mechanics". A related notion is the ER = EPR conjecture of Maldacena and Susskind, relating entanglement to wormholes. In some sense, we're making this proposal a bit more specific, by giving a formula for distance as a function of entanglement.