Quantum Physics

Using quantum control in foundational experiments allows new theoretical and experimental possibilities. We show how, e.g.,  quantum controlling devices reverse a temporal ordering in  detection. We consider probing of wave–particle duality in   quantum-controlled and the entanglement-assisted delayed-choice experiments. Then we discuss other situations where quantum control may be useful, and finally demonstrate how the techniques we developed are applied to the study of  consistency of the classically reasonable requirements.  In a version of the delayed-choice experiment which ostensibly combines determinism, independence of hidden variables on the conducted experiments, and wave-particle objectivity we show that these ideas are incompatible with any theory, not only with quantum mechanics.

 It is well known - to those who know it - that noise and randomness can enhance signal resolution. I'll present an easy-to-follow example from digital audio that illustrates the way in which adding noise ("dither") prior to measurement enhances the accuracy with which we are able to distinguish the features of the sound or image. I will then explore the way in which the environmental interactions prior to measurement ordinarily characterized as environment-induced decoherence may play a similar role.  The paradoxical conclusion is that the quasiclassical behavior associated with such systems may be a more accurate representation of the quantum world than what we think of as fully "quantum" behavior, which may in turn be artifactual, the result of errors similar to those introduced by the discretization (also known as "quantization") of data in digital audio and imaging.

We present a formal logic modeling some aspects of the behavior of the quantum measurement process, and study some properties of the models of this logic, from which we deduce some characteristics that any such model should verify. In the case of a Hilbert space of dimension at least 3, we then show that no model can lead to the prediction with certainty of more than one atomic outcome. Moreover, if the Hilbert space is finite dimensional, we can precisely describe the structure of the predictions of any model of our logic. As a consequence, we also prove that all the models of our logic make exactly the same predictions regarding whether a given sequence of outcomes is possible.