A protocol using cross‐entangled independent Einstein‐Podolsky‐Rosen (EPR) beams is developed as a means of sending information faster than light (FTL) by taking advantage of quantum nonlocality and indistinguishable particle statistics. Two observers bracket a central midpoint transmitter that contains dual EPR sources from which bits are encoded in packets of photon pairs. FTL communication occurs between the observers in a simplex mode. A reformulation of quantum mechanics is proposed that permits such communications, as well as wave function collapse, to be relativistically consistent, while also resolving the problem of causal ordering normally associated with spacelike connections. The issue of temporal paradox is handled separately at both the quantum and classical levels. Spacelike causal connections lead to closed loops in spacetime and causal self‐reference. It is shown that such self‐reference leads to nonlinearities in the evolution of the wave function that may be sufficient to lead to wave function collapse.
A protocol using cross‐entangled independent Einstein‐Podolsky‐Rosen (EPR) beams is developed as a means of sending information faster than light (FTL) by taking advantage of quantum nonlocality and indistinguishable particle statistics. Two observers bracket a central midpoint transmitter that contains dual EPR sources from which bits are encoded in packets of photon pairs. FTL communication occurs between the observers in a simplex mode. A reformulation of quantum mechanics is proposed that permits such communications, as well as wave function collapse, to be relativistically consistent, while also resolving the problem of causal ordering normally associated with spacelike connections. The issue of temporal paradox is handled separately at both the quantum and classical levels. Spacelike causal connections lead to closed loops in spacetime and causal self‐reference. It is shown that such self‐reference leads to nonlinearities in the evolution of the wave function that may be sufficient to lead to wave function collapse.
In the current formalism of quantum mechanics, collapse of the wave function is envisioned as occurring “instantaneously”. Since this is in conflict with the fact that “simultaneity” is not a relativistic invariant, quantum mechanics and relativity are in conflict with each another. This conflict is benign as long as faster-than-light (FTL) phenomena are disallowed. This paper explores this conflict and considers the implications if collapse can be specified to occur in a way that is consistent with relativity. In particular, relativistically consistent wave function collapse forces us to reconsider our preconceptions of causality. We are led to consider two cases; timelike and spacelike. For two events that are causally connected by a timelike interval, the earlier-in-time event is the cause in all reference frames, but the spatial ordering is not preserved. For two events that are causally connected by a spacelike interval, the temporal ordering is not preserved but the spatial ordering is, just the reverse. This is philosophically disturbing since for spacelike causes half the reference frames see the cause as proceeding backwards in time. However, in and of itself this is not logically inconsistent. Backwards-in-Time Causality (BTC) seems at first glance to permit temporal paradox, since two spacelike causal connections can be used to create a closed causal loop in spacetime. While temporal paradox is logically inconsistent, BTC can still be allowed if there is also a censor mechanism that prevents temporal paradox. In relativity, FTL and BTC are two sides of the same coin, so the major implication of relativistically consistent wave function collapse is that quantum systems should be able to support both FTL and BTC phenomena despite Eberhard’s “proof.”
Schrödinger held that a local quantum system has some objectively real quantum state and no other (hidden) properties. He therefore took the Einstein-Podolsky-Rosen (EPR) phenomenon, which he generalized and called `steering', to require nonlocal wavefunction collapse. Because this would entail faster-than-light (FTL) information transmission, he doubted that it would be seen experimentally. Here we report a demonstration of EPR steering with entangled photon pairs that puts--in Schrödinger's interpretation--a non-zero lower bound on the amount of FTL information transmission. We develop a family of n-setting loss-tolerant EPR-steering inequalities allowing for a size-d classical message sent from Alice's laboratory to Bob's. For the case n=3 and d=2 (one bit) we observe a statistically significant violation. Our experiment closes the efficiency and locality loopholes, and we address the freedom-of-choice loophole by using quantum random number generators to independently choose Alice's and Bob's measurement basis settings. To close the efficiency and locality loopholes simultaneously, we introduce methods for quickly switching between three mutually unbiased measurement bases and for accurately characterizing the efficiency of detectors. From the space-time arrangement of our experiment, we can conclude that if the mechanism for the observed bipartite correlations is that Alice's measurement induces wave-function collapse of Bob's particle, then more than one bit of information must travel from Alice to Bob at more than three times the speed of light.
It has been advocated by Bell and Bohm that the Einstein-Podolsky-Rosen (EPR) correlations are mediated through faster-than-light (FTL) interactions. In a previous paper a way to avoid causal paradoxes derived from this FTL hypothesis (via the breakdown of Lorentz symmetry) has been suggested. Lorentz transformations would remain valid, but there would be no equivalence between active and passive Lorentz transformations in the case of EPR correlations. Some counterintuitive consequences of this assumption are briefly examined here.
A thought experiment is presented that provides a hint as to how quantum wave functions can collapse in a relativistically consistent way. The thought experiment consists of a central source of photon pulses midway between two detectors, which is examined relativistically from both the lab frame and a frame moving with respect to the source and detectors. The total number of pulses between the two detectors is the only invariant and this leads to the idea that collapse might occur along special spacetime intervals, which we call symmetric spacetime intervals. In the current formalism of quantum mechanics, collapse is envisioned to occur “instantaneously”, in clear violation of relativity. It is shown that what the current formalism actually specifies is that collapse is merely spacelike. However, if quantum collapse occurs along symmetric spacetime intervals, then collapse of the wave function can be made consistent with relativity and all observers can agree upon which of two spacelike-separated causally connected events is the cause and which the effect. Nomenclature x = normalized distance in light seconds (ls) t = normalized time in seconds (s) γ = Lorentz factor s = spacetime interval u = normalized velocity (ls/s) c = speed of light (1.0 ls/s) y = a quantum object z = a quantum object d = separation between pulses (ls) L = separation between detectors (ls) ν = frequency (s-1) n = number of pulses β = slope of the symmetric interval (s/ls) I.
In previous work, the case has been made that the nonlocality of quantum systems implies some kind of spacelike causal connection, and that for this connection to be physically real, it must meet several very rigid constraints. Step by step, a reformulation of quantum mechanics has been developed that meets these constraints. These constraints include relativistic consistency, causality, and some way to avoid temporal paradox. The reformulation of quantum mechanics to meet these criteria has yielded a hypothesis that cyclically entangled quantum systems provide an objective measurement mechanism. This hypothesis has stood up well in abstract quantum systems where the superpositions are unweighted. This paper continues the effort by considering the case for cyclic entanglements when the superpositions have complex weights. It is shown that in general, a cyclic entanglement is self-referential in only one basis and it is in this basis that collapse occurs. Thus, cyclic entanglements provide both the nonlinearity and the symmetry breaking necessary for a quantum system to self-collapse. This removes the confusing and ambiguous requirement for an outside observer (which ultimately is just another quantum system) to perform the measurement act. This reformulation of quantum mechanics permits relativistically consistent superluminal communications and paradox-free backwards-intime causality.
A relativistic version of the (consistent or decoherent) histories approach to quantum theory is developed on the basis of earlier work by Hartle, and used to discuss relativistic forms of the paradoxes of spherical wave packet collapse, Bohm's formulation of the Einstein-Podolsky-Rosen paradox, and Hardy's paradox. It is argued that wave function collapse is not needed for introducing probabilities into relativistic quantum mechanics, and in any case should never be thought of as a physical process. Alternative approaches to stochastic time dependence can be used to construct a physical picture of the measurement process that is less misleading than collapse models. In particular, one can employ a coarse-grained but fully quantum-mechanical description in which particles move along trajectories, with behavior under Lorentz transformations the same as in classical relativistic physics, and detectors are triggered by particles reaching them along such trajectories. States entangled between spacelike separate regions are also legitimate quantum descriptions, and can be consistently handled by the formalism presented here. The paradoxes in question arise because of using modes of reasoning which, while correct for classical physics, are inconsistent with the mathematical structure of quantum theory, and are resolved (or tamed) by using a proper quantum analysis. In particular, there is no need to invoke, nor any evidence for, mysterious long-range superluminal influences, and thus no incompatibility, at least from this source, between relativity theory and quantum mechanics.