Abstract
We present a path analysis of the condition under which the outcomes of previous observation affect the results of the measurements yet to be made. It is shown that this effect, also known as “signalling in time”, occurs whenever the earlier measurements are set to destroy interference between two or more virtual paths. We also demonstrate that Feynman’s negative “probabilities” provide for a more reliable witness of “signalling in time”, than the Leggett-Garg inequalities, while both methods are frequently subject to failure.
Highlights
We present a path analysis of the condition under which the outcomes of previous observation affect the results of the measurements yet to be made
The authors of1 have shown that superconducting flux qubits possess, despite their macroscopic nature, such quantum properties, as the ability to exist in a superposition of distinct states
After reviewing an approach based on the so-called Leggett-Garg inequalities (LGI), which may or may not be satisfied by certain quantum mechanical averages2, they chose to employ a simpler experimental protocol
Summary
On the horizontal and diagonal dark lines, the system is “classical stochastic” There a single path [see inset b) in Fig. 2], which leads to a unique final state, and is travelled every time the experiment is repeated, regardless of whether the measurement at t = τ is made, or not. We expect to have no access to the current actual value(s) of the “hidden variable(s)” λ It is assumed, that each time the system is set to evolve from its initial state, particular path probabilities For our assumption to be pc3o(rQre3c|Qt,2w, eQn1,eeλd)pto2(dQe2m|Qo1n,sλtr)aetexitshta, tetvheencilfanssoicmalepasruobreambielintitessa(rsemmaalldpe’s. Different measurements may produce statistical ensembles with distributions as different as the distributions of heads and tails for differently skewed coins This will happen whenever an additional earlier measurement destroys interference between virtual paths leading to later outcomes
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