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arXiv:1807.06586 · Quantum Science and Technology

From counterportation to local wormholes

Hatim Salih

Published Sep 2, 2022• 13 citations
arXivHTMLPDF

Abstract

Abstract We propose an experimental realisation 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. We employ cavity quantum electrodynamics, estimating resources for beating the classical fidelity limit—except, unlike teleportation, no pre-shared entanglement nor classical communication are required. Our 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. We go on to characterise 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.

DOI
10.1088/2058-9565/ac8ecd

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Comment on ‘From counterportation to local wormholes’

Justin Dressel, Gregory Reznik, Lev Vaidman A

Abstract Hatim Salih discovered a method for transferring a quantum state with no particles present in the transmission channel, which he named counterportation. Recently (Salih 2023 Quantum Sci. Technol. 8 025016), he presented a feasible procedure for its implementation. The modification of the protocol by Aharonov and Vaidman, adopted by Salih, justifies the claim that no photons were present in the transmission channel during counterportation. We argue, however, that there is an error in this paper. The analysis of a simplified protocol, which questions the validity of the two-state vector formalism description of the photon presence in the communication channel, is incorrect.

Quantum Science and Technology•Dec 19, 2023•2 citations
Abstract We propose an experimental realisation 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. We employ cavity quantum electrodynamics, estimating resources for beating the classical fidelity limit—except, unlike teleportation, no pre-shared entanglement nor classical communication are required. Our 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. We go on to characterise 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.
Abstract We uncover a new quantum paradox, where a simple question about two identical quantum systems reveals unsettlingly paradoxical answers when weak measurements are considered. Our resolution of the paradox, from within the weak measurement framework, amounts to a demonstration of exchange-free communication for the generalised protocol for sending an unknown qubit without any particles travelling between the communicating parties, i.e. counterfactually. The paradox and its resolution are reproduced from a consistent-histories viewpoint. We go on to propose a novel, experimentally feasible implementation of this counterfactual disembodied transport that we call counterportation, based on cavity quantum electrodynamics, estimating resources for beating the no-cloning fidelity limit---except that unlike teleportation no previously-shared entanglement nor classical communication are required. Our approach is several orders of magnitude more efficient in terms of physical resources than previously proposed techniques, while being remarkably tolerant to device imperfections, paving the way for an experimental demonstration. Surprisingly, while counterfactual communication is intuitively explained in terms of interaction-free measurement and the Zeno effect, we show based on our proposed scheme that neither is necessary, with implications in support of an underlying physical reality.
We uncover a new quantum paradox, where a simple question about two identical systems of nested interferometers reveals surprising answers on the whereabouts of a photon, when considering weak measurements. The paradox is reproduced using consistent histories. Our resolution of the paradox amounts to a proof of counterfactuality - communication without particle exchange - for our protocol for communicating an unknown qubit without exchanging any particles. We go on to propose a feasible implementation of this disembodied transport, estimating resources for beating the classical limit, except that, unlike teleportation, no previously-shared entanglement nor classical communication are required. Moreover, while counterfactual communication can be intuitively explained in terms of interaction-free measurement and the Zeno effect, we show that, surprisingly, neither is necessary - with direct implications in support of the reality of the wave-function.
Quantum teleportation circumvents the uncertainty principle using dual channels: a quantum one consisting of previously-shared entanglement, and a classical one, together allowing the disembodied transport of an unknown quantum state over distance. It has recently been shown that a classical bit can be counterfactually communicated between two parties in empty space, “Alice” and “Bob”. Here, by using our “dual” version of the chained quantum Zeno effect to achieve a counterfactual CNOT gate, we propose a protocol for transporting an unknown qubit counterfactually, that is without any physical particles travelling between Alice and Bob—no classical channel and no previously-shared entanglement.
A bstract The rapid development of quantum science and technology is leading us into an era where quantum many-body systems can be comprehended through quantum simulations. Holographic duality, which states gravity and spacetime can emerge from strongly interacting systems, then offers a natural avenue for the experimental study of gravity physics without delving into experimentally infeasible high energies. A prominent example is the simulation of traversable wormholes through the wormhole teleportation protocol, attracting both theoretical and experimental attention. In this work, we develop the theoretical framework for computing the fidelity of wormhole teleportation in N -qubit systems with all-to-all interactions, quantified by mutual information and entanglement negativity. The main technique is the scramblon effective theory, which captures universal out-of-time-order correlations in generic chaotic systems. We clarify that strong couplings between the two systems are essential for simulating the probe limit of semi-classical traversable wormholes using strongly interacting systems with near-maximal chaos. However, the teleportation signal diminishes rapidly when reducing the system size N , requiring a large number of qubits to observe a sharp signature of emergent geometry by simulating the Sachdev-Ye-Kitaev model. This includes both the causal time-order of signals and the asymmetry of the teleportation signal for coupling with different signs. As a comparison, the teleportation signal increases when reducing N in weakly interacting systems. We also analyze the fidelity of the generalized encoding scheme in fermionic string operators.
We show that two unknown quantum states, either pure or mixed, can be bidirectionally ``teleported'' counterfactually. In the process of information exchange, there is no physical particle traveling between two communicators. Unlike conventional quantum teleportation, our protocol requires neither prearranged entangled pairs nor Bell measurements. We entangle and disentangle a photon and an atom through multiple measurements in a special sequence. These multiple measurements can smoothly but reversibly control system evolution. The total effect of multiple measurements can be considered as a unitary time evolution operator. Therefore, our protocol can be regarded as a counterfactual quantum swap gate. Based on our approach, all known conventional quantum gates can be counterfactualized.
Abstract Hatim Salih discovered a method for transferring a quantum state with no particles present in the transmission channel, which he named counterportation. Recently (Salih 2023 Quantum Sci. Technol. 8 025016), he presented a feasible procedure for its implementation. The modification of the protocol by Aharonov and Vaidman, adopted by Salih, justifies the claim that no photons were present in the transmission channel during counterportation. We argue, however, that there is an error in this paper. The analysis of a simplified protocol, which questions the validity of the two-state vector formalism description of the photon presence in the communication channel, is incorrect.