Quantum Communication Without Exchanging Particles

A University of Bristol physicist provides the first-ever practical blueprint for creating in the lab a wormhole that verifiably bridges space, as a probe into the inner workings of the universe. It involves creating a new kind of quantum computer, investigation of quantuum physics in a new way and a possible path to some kind of wormhole science or technology.

He calls the new method ‘counterportation’. Study author Hatim Salih, Honorary Research Fellow at the university’s Quantum Engineering Technology (QET) Labs, is co-founder of the start-up DotQuantum.

“If counterportation is to be realized, an entirely new type of quantum computer has to be built: an exchange-free one, where communicating parties exchange no particles,” Hatim said.

In their conception, a local wormhole is a physical system characterized by the no-cloning of information that mediates the action of an exchange-free quantum computer: locally induced spatial entanglements of a single particle, and corresponding self-interference scenarios allow entangling other degrees of freedom among spatially separated parties, without any particle observably crossing—rendering space disjunctly traversabile.

A constructor-theoretic approach has thus enabled us to precisely characterise a local ER bridge in terms of a task/constructor pairing, namely the disjunct traversability of space by means of an exchange-free quantum computer, without assuming any specific quantum gravity dynamics. Explaining counterportation, EPR provides a dynamical account of how a local wormhole mediates qubit exchange-free interaction.

The lab demonstration requires what is essentially a two-qubit exchange-free quantum computer. By contrast to large-scale quantum computers that promise remarkable speed-ups, the promise of exchange-free quantum computers of even the smallest scale is to make seemingly impossible tasks possible by incorporating space fundamentally. Ultimately, they see exchange-free quantum computers coming into their own exploring the fundamental physics of the Universe.

Accomplishing the mission of counterporting an object across space—thereby traversing a local wormhole, as if through an extra spatial dimension—comes down to locally induced spatial entanglements of a single particle, and corresponding self-interference scenarios at work. But as Richard Feynman was quick to point out, such interference ‘has in it the heart of quantum mechanics.’ Even further, the uncovered phenomenon of counterportation provides a smoking gun for the existence of an underlying physical reality.

Researchers propose an experimental realization of the protocol for the counterfactual disembodied transport of an unknown qubit—or what we call counterportation—where sender and receiver, remarkably, exchange no particles. They employ cavity quantum electrodynamics, estimating resources for beating the classical fidelity limit—except, unlike teleportation, no pre-shared entanglement nor classical communication are required. The approach is multiple orders of magnitude more efficient in terms of physical resources than previously proposed implementation, paving the way for a demonstration using existing imperfect devices. Surprisingly, while such communication is intuitively explained in terms of ‘interaction-free’ measurement and the Zeno effect, we show that neither is necessary, with far-reaching implications in support of an underlying physical reality. They go on to characterize an explanatory framework for counterportation starting from constructor theory: local wormholes. Conversely, a counterportation experiment demonstrating the traversability of space, by means of what is essentially a two-qubit exchange-free quantum computer, can point to the existence in the lab of such traversable wormholes.

Universal exchange-free quantum computation

The exchange-free CNOT gate is the key primitive for the protocol for the counterfactual disembodied transport of an unknown qubit, counterportation.

The gate itself was the earliest counterfactual gate to be proposed, two-qubit or otherwise, and allows universal exchange-free quantum computation as a new computing paradigm. The definition of counterfactuality, with the target qubit of the gate at one subsystem, Alice, and the control qubit at another, Bob, is that the two spatially-separated subsystems exchange no particles during the computation. Bristol researchers use the circular polarisation basis as it ties better with our experimental proposal for Bob’s qubit. They provide a more succinct derivation in what follows before showing how to incorporate an improvement based on recent work by Aharonov and Vaidman, so as to establish broad agreement on counterfactuality. Aharonov and Vaidman’s improvement is therefore readily adopted as an integral part of our exchange-free gate. Consider a right-circular polarised, R, photon entering the top chained quantum Zeno effect module CQZE1 in figure 2(C).

20 thoughts on “Quantum Communication Without Exchanging Particles”

  1. IIRC, FTL communication via quantum entanglement was impossible because the quantum state was loss once it was measured. Now that physical entanglement is not necessary, what other technicality will make FTL communication impossible.

  2. “The lab demonstration requires what is essentially a two-qubit exchange-free quantum computer.”

    How to make a wormhole.

    1. First, obtain a wormhole.
    2. Demonstrate that you have a wormhole.

  3. It’s nice to see the Constructor Theory people getting to work on applications that may give the theory some prediction chops. The concept (of Constructor Theory) is quite an interesting idea, trying to probe physics through computation theory methods.

  4. Stuff like this makes me wonder if we’ll finally be able to tune into whatever communications other civilizations are using.

    it is scientifically impossible for there not to be other intelligent life out there, so why don’t we see or hear them?

        • It’s kinda unlikely we’re the only intelligent life in the universe, because the universe is BIG.

          We may well be the only intelligent life in the Milky Way galaxy, though, with the nearest competitor so far away we’ll never meet them, and be lucky even to detect them. Or not.

          Kind of early to try to say for sure.

          • We don’t need to be the only intelligent life in the Universe; it’s enough if we’re the only intelligent life in our own light cone. And considering accelerating expansion, it may be that before we detect the next civilization over they may fly out of our maximum causal bubble; if that happens, they might as well not exist, as far as we’re concerned.

    • It’s very plausible for there not to be any technological civilizations near enough to be detectable or to matter to us even if there happen to be quite a few in the universe at present.

  5. Message for Tesla: Please don’t finalize Cybertruck!
    I have solutions for Cybertruck bad wiper and many more problems for Semi and Roadster please send to Elon Musk or Franz von Holzhausen….
    Thanks. Best regards: Joe

  6. Its not a real wormhole that you can send things through. Rather, it is a quantum phenomenon that allows for quantum states to be passed without the use of physical particles.

        • From what I read, entangled particles may in fact be connected via tiny wormholes. This may also be related to entropy.
          At least, that is one possible explanation.

      • OK, assuming that to be the case, when will they be able to scale up the size of these wormholes to allow people to walk though them so I no longer have to sit through a 12 hour flight?

        • Joke’s on you: If the mouths of a wormhole are 1,000 km apart, the interior is 1,000 km long.

          The only reason anybody ever assumed otherwise was the convenience of SF writers…

          • I’ve always sort of wondered about that. In order to make it useful for space travel, other types of things would need to happen, and I’m not sure what those things would be (beyond what might be the warping of spacetime).

            • Heinlein, in Starman Jones, largely originated the idea. The excuse for the wormholes being short was that the universe was actually compactly “crumpled” in higher dimensions, so that places that were far apart going through normal space were adjacent if you could cut across higher dimensions in the right spot.

              But if the universe were really bent like that in higher dimensions, we’d know it, because spacial curvature creates gravity. A crumpled universe would be very conspicuous.

              The truth is, there’s no reason to think wormholes would actually be shortcuts.


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