Superluminal Signalling by Path Entanglement

Remi Cornwall

Published Oct 1, 2014• 5 citations

Abstract

Entanglement studies dwell on multi-particle systems by definition – one particle, via a global symmetry/conservation law is correlated to another. It has often been wondered via EPR/Bell/Aspect/Dopfer-Zeilinger/Zbinden whether: first, a communication scheme is possible by entangled quantum state collapse and secondly, whether such a scheme would work over spacelike separations. This study follows on from the author’s earlier scheme of sending classical data over a Bell Channel, to now, using an unentangled source. The rationale for this is that single particles are entangled with the vacuum state in path entanglement by the principle of conservation of probability: measurement of a photon in one path causes a collapse of the wavefunction in all the others. The new communication scheme represents an improvement over using expensive and complicated entangled sources of poor purity, for common-or-garden coherent sources.

Related papers

Superluminal Signalling without the use of Entangled Particles

Remi Cornwall

Entanglement studies dwell on multi-particle systems by definition – one particle, via a global symmetry/conservation law is correlated to another. It has often been wondered via EPR/Bell/Aspect/Dopfer-Zeilinger/Zbinden whether: first, a communication scheme is possible by entangled quantum state collapse and secondly, whether such a scheme would work over spacelike separations. This study follows on from the author’s earlier scheme of sending classical data over a Bell Channel, to now, using an unentangled source. The rationale for this is that beams from a threeway or n-way splitter (even with single photons) are in a sense “entangled” with themselves via the principle of conservation of probability: measurement of a photon in one beam causes a collapse of the wavefunction in all the others. The new communication scheme represents an improvement over using expensive and complicated entangled sources of poor purity, for common-or-garden coherent sources.

Jan 1, 20141 citation

Secure Quantum Communication and Superluminal Signalling on the Bell Channel

Remi Cornwall

A means and protocol is presented to send information on the Bell Channel to achieve the effect of superluminal signalling. The method is to use detection of a photon entangled state as one binary digit and either of the collapsed states as the complement digit - this is the protocol. The means to affect this detection is by use of an interferometer set-up able to resolve two interfering pathways corresponding to the two polarization states of the photon. To achieve interference of the horizontal and vertical components Faraday rotators are used to bring both components into diagonal polarization, this operation is unitary. Modulation is caused by the remote signaller collapsing one aspect of the photon wavefunction; a physically secure channel sending information superluminally results. A preliminary discussion into the clash and the hopeful resolution with Relativity theory is presented - it is noteworthy that at the instant of transmission between the two stations that there is no transfer of mass-energy to instigate communication but the transmission of a quantum state - pure information only.

arXiv:1106.2257Jun 11, 201113 citations

Introduction

Alisa Bokulich, Gregg S. Jaeger

Entanglement can be understood as an extraordinary degree of correlation between states of quantum systems – a correlation that cannot be given an explanation in terms of something like a common cause. Entanglement can occur between two or more quantum systems, and the most interesting case is when these correlations occur between systems that are space-like separated, meaning that changes made to one system are immediately correlated with changes in a distant system even though there is no time for a signal to travel between them. In this case one says that quantum entanglement leads to non-local correlations, or non-locality. More precisely, entanglement can be defined in the following way. Consider two particles, A and B, whose (pure) states can be represented by the state vectors ψA and ψB. Instead of representing the state of each particle individually, one can represent the composite two-particle system by another wavefunction, Ψ AB. If the two particles are unentangled , then the composite state is just the tensor product of the states of the components: Ψ AB = ψ A ⊗ ψ B; the state is then said to be factorable (or separable). If the particles are entangled, however, then the state of the composite system cannot be written as such a product of a definite state for A and a definite state for B. This is how an entangled state is defined for pure states: a state is entangled if and only if it cannot be factored: Ψ AB ≠ ψ A ⊗ ψ B.

Cambridge University Press eBooksJun 10, 20100 citations

In search of superluminal quantum communications: recent experiments and possible improvements

B Cocciaro, S Faetti, L Fronzoni

As shown in the famous EPR paper (Einstein, Podolsky e Rosen, 1935), Quantum Mechanics is non-local. The Bell theorem and the experiments by Aspect and many others, ruled out the possibility of explaining quantum correlations between entangled particles using local hidden variables models (except for implausible combinations of loopholes). Some authors (Bell, Eberhard, Bohm and Hiley) suggested that quantum correlations could be due to superluminal communications (tachyons) that propagate isotropically with velocity v t > c in a preferred reference frame. For finite values of v t , Quantum Mechanics and superluminal models lead to different predictions. Some years ago a Geneva group and our group did experiments on entangled photons to evidence possible discrepancies between experimental results and quantum predictions. Since no discrepancy was found, these experiments established only lower bounds for the possible tachyon velocities v t . Here we propose an improved experiment that should lead us to explore a much larger range of possible tachyon velocities V t for any possible direction of velocity of the tachyons preferred frame.

arXiv:1304.2282Journal of Physics Conference SeriesJun 10, 20135 citations

Noncausal Superluminal Nonlocal Signalling

R. Srikanth

We propose a thought experiment for classical superluminal signal transmission based on the quantum nonlocal influence of photons on their momentum entangled EPR twins. The signal sender measures either position or momentum of particles in a pure ensemble of the entangled pairs, leaving their twins as localized particles or plane waves. The signal receiver distinguishes these outcomes interferometrically using a double slit interferometer modified by a system of optical filters. Since the collapse of the wavefunction is postulated to be instantaneous, this signal can be transmitted superluminally. We show that the method circumvents the no-signalling theorem because the receiver is able to modify the disentangled wavefunction before his measurement. We propose a plan for the possible practical realization of a superluminal quantum telegraph based on the thought experiment.

arXiv:quant-ph/9904075Apr 20, 19992 citations

Superdense Coding and Quantum Teleportation

Phillip Kaye, Raymond Laflamme, Michele Mosca

We are now ready to look at our first protocols for quantum information. In this section, we examine two communication protocols which can be implemented using the tools we have developed in the preceding sections. These protocols are known as superdense coding and quantum teleportation. Both are inherently quantum: there are no classical protocols which behave in the same way. Both involve two parties who wish to perform some communication task between them. In descriptions of such communication protocols (especially in cryptography), it is very common to name the two parties ‘Alice’ and ‘Bob’, for convenience. We will follow this tradition. We will repeatedly refer to communication channels. A quantum communication channel refers to a communication line (e.g. a fiberoptic cable), which can carry qubits between two remote locations. A classical communication channel is one which can carry classical bits (but not qubits).1 The protocols (like many in quantum communication) require that Alice and Bob initially share an entangled pair of qubits in the Bell state The above Bell state is sometimes referred to as an EPR pair. Such a state would have to be created ahead of time, when the qubits are in a lab together and can be made to interact in a way which will give rise to the entanglement between them. After the state is created, Alice and Bob each take one of the two qubits away with them. Alternatively, a third party could create the EPR pair and give one particle to Alice and the other to Bob. If they are careful not to let them interact with the environment, or any other quantum system, Alice and Bob’s joint state will remain entangled. This entanglement becomes a resource which Alice and Bob can use to achieve protocols such as the following. Suppose Alice wishes to send Bob two classical bits of information. Superdense coding is a way of achieving this task over a quantum channel, requiring only that Alice send one qubit to Bob. Alice and Bob must initially share the Bell state Suppose Alice is in possession of the first qubit and Bob the second qubit.

Oxford University Press eBooksNov 16, 20060 citations