A postal money order doesn't arrive instantly but after a set delay, and the amount credited to the recipient's account ends up larger than what the sender deposited in cash. That's roughly how the new protocol, dubbed temporal quantum energy teleportation (TQET), works.
In ordinary quantum energy teleportation, two parties, Alice and Bob, share a common quantum state. Alice measures her part and tells Bob the result, who then performs the necessary operation to extract energy from his slice of the system. Here, energy is transferred instantaneously, as soon as the signal arrives. In the new protocol, Bob waits for some time after Alice's measurement, and because the system continues to evolve on its own, he ends up with noticeably more.
The physical mechanism relies on quantum correlations stretched across time. The energy supplier (Alice) injects energy into the system by measuring the ground state of many particles, while the distant receiver (Bob) performs a conditional operation after waiting for the response. When Bob acts immediately, the protocol reduces to the earlier version (QET). The delay, however, allows the use of temporal entanglement — a special kind of connection between the system's past and future states.
This approach doesn't violate conservation laws: energy isn't conjured from nowhere but extracted from correlations embedded in the initial state. Practical benefits could emerge in quantum batteries or networks where it's important to transfer energy wirelessly and with minimal losses. And perhaps one day we'll be able to charge future devices simply by "making a deal" with the quantum past.
Ordinary quantum teleportation transfers a particle's state, not the particle itself, like a fax machine that recreates a document at the other end while destroying the original. Energy teleportation goes further: it transfers the ability to do work without moving any matter.
In Isaac Asimov's novel The End of Eternity, trade in energy between different eras is described — the new protocol takes a first step toward such exchange, albeit in the microworld.