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From a Quantum Paradox to Provably Counterfactual Disembodied Transport: Counterportation

Hatim Salih

Published Jul 17, 2018• 0 citations
OpenAlex

Abstract

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.

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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.
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.
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.
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.
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 Counterfactual quantum communication is one of the most interesting facets of quantum communication, allowing two parties to communicate without any transmission of quantum or classical particles between the parties involved in the communication process. This aspect of quantum communication originates from the interaction-free measurements where the chained quantum Zeno effect plays an important role. Here, we propose a new counterfactual quantum communication protocol for transmitting an entangled state from a pair of electrons to two independent photons. Interestingly, the protocol proposed here shows that the counterfactual method can be employed to transfer information from house qubits to flying qubits. Following this, we show that the protocol finds uses in building quantum repeaters leading to a counterfactual quantum network, enabling counterfactual communication over a linear quantum network.
We demonstrate quantum information can be transferred between two distant participants without any physical particles traveling between them. The key procedure of the counterfactual scheme is to entangle two nonlocal qubits with each other without interaction, so the scheme can also be used to generate nonlocal entanglement counterfactually. We here illustrate the scheme by using flying photon qubits and Rydberg atom qubits assisted by a mesoscopic atomic ensemble. Unlike the typical teleportation, the present scheme can transport an unknown qubit in a nondeterministic manner without prior entanglement sharing or classical communication between the two distant participants.