Methods used to observe a dynamical quantum nonlocality effect in a twin Mach–Zehnder interferometer

Abstract

Straightforward novel methods for stabilizing, tuning, and controlling a twin Mach-Zehnder interferometer for the purpose of observing a subtle dynamical quantum nonlocality effect in a recent optical experiment are presented and discussed. Weak measurements were required for observing a subtle quantum dynamical nonlocality effect that reveals itself in a change of a weak value. Consequently, emphasis is placed upon describing the approaches to apparatus stabilization and interaction strength control between photons and the apparatus. The details discussed in this paper should be of general interest to experimentalists engaging in weak measurement and weak value research.

Paradoxical behavior in a triple cascade of Mach–Zehnder interferometers

“…It is noteworthy that the large occupation number feature of this cascade apparatus can be exploited to measure small transverse displacements of mirrors M3 or M4. As discussed in [15,16], a small transverse displacement of a mirror in an MZI corresponds to a weak measurement of the photon occupation number at the mirror. In this case, an appropriately small mirror displacement γ of M3 provides the required weak interaction.…”

Capacity and Entropy of a Retro-Causal Channel Observed in a Twin Mach-Zehnder Interferometer During Measurements of Pre- and Post-Selected Quantum Systems

“…Inspired by a weak value gedanken experiment discussed by Tollaksen et al [13], an optical twin Mach-Zehnder interferometer (MZI) experiment was performed in 2010 which confirmed the predictions made by the gedanken experiment and provided indirect experimental evidence that single particle quantum interference phenomena can be explained in terms of a non-local exchange of modular momentum [14,15]. A recent re-analysis of the reduced 2010 experimental data also suggests that a possible retro-causal channel was observed in the twin MZI apparatus during the associated measurements of ensembles of pre-selected and post-selected (PPS) quantum systems [16,17].…”

Exact pointer theories for von Neumann projector measurements of pre- and postselected and preselected-only quantum systems: statistical mixtures and weak value persistence

“…Each of these translations yielded a PPS measurement of in which the associated mirror displacement corresponded to the interaction strength γ and produced a transverse shift in the observed spatial distribution profile of the light exiting one of the ports in the output beamsplitter of the second MZI. The mean position of this profile in the laboratory reference frame served as the measurement pointer (for additional theoretical and experimental details the reader is invited to consult [25][26][27]). …”

“…These operators are also interesting because the measurement and interpretation of their weak values have played a central role in the theoretical and experimental resolutions of the 'quantum box problem' [16][17][18] and 'Hardy's paradox' [19][20][21][22][23]. More recently, projector weak values have also been used to investigate paradoxical behaviour in Mach-Zehnder interferometers (MZIs) [24] and employed in experimental observations of dynamical quantum non-locality-induced effects [25][26][27].…”