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Recently it has been pointed out that an outstanding application of an IBM quantum computer is to reverse the arrow of time (Lesovik et al., 2019). It is explored such a possibility in a two qubits system coupled to a common structured reservoir at zero temperature. It is shown that population rates of the quantum states become the same both towards the remote past and towards the remote future. A two qubits system in presence of noise can reverse the arrow of time.

Copyright of Foreign Literature Studies is the property of Foreign Literature Studies and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recently it has been pointed out that an outstanding application of an IBM quantum computer is to reverse the arrow of time (Lesovik et al., 2019). It is explored such a possibility in a quantum computer composed by a two qubits system coupled to a common structured reservoir at zero temperature. The requirement of zero temperature is for avoiding the unwanted quantum noise due to dissipation of energy and decoherence in such a quantum computer. It is shown that population rates of the quantum states become the same both towards the remote past and towards the remote future. A two qubits system in presence of noise can reverse the arrow of time. Such a result opens the way for exploring such a possibility in another different quantum devices. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Data Acquisition & Processing / Shu Ju Cai Ji Yu Chu Li is the property of Editorial Department of Journal of Nanjing University of Aeronautics & Astronautics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Echo protocols provide a means to investigate the arrow of time in macroscopic processes. Starting from a nonequilibrium state, the many-body quantum system under study is evolved for a certain period of time τ. Thereafter, an (effective) time reversal is performed that would – if implemented perfectly – take the system back to the initial state after another time period τ. Typical examples are nuclear magnetic resonance imaging and polarisation echo experiments. The presence of small, uncontrolled inaccuracies during the backward propagation results in deviations of the "echo signal" from the original evolution and can be exploited to quantify the instability of nonequilibrium states and the irreversibility of the dynamics. We derive an analytic prediction for the typical dependence of this echo signal for macroscopic observables on the magnitude of the inaccuracies and on the duration τ of the process, and verify it in numerical examples. [ABSTRACT FROM AUTHOR]

The crystallographic symmetry of time‐periodic phenomena has been extended to include time inversion. The properties of such spatio‐temporal crystallographic point groups with time translations and time inversion are derived and one representative group from each of the 343 types has been tabulated. In addition, stereographic symmetry and general‐position diagrams are given for each representative group. These groups are also given a notation consisting of a short Hermann–Mauguin magnetic point‐group symbol with each spatial operation coupled with its associated time translation. [ABSTRACT FROM AUTHOR]

Objective. Ultrasound neuromodulation has become an emerging method for the therapy of neurodegenerative and psychiatric diseases. The phased array ultrasonic transducer enables multi-target ultrasound neuromodulation in small animals, but the relatively large size and mass and the thick cables of the array limit the free movement of small animals. Furthermore, spatial interference may occur during multi-target ultrasound brain stimulation with multiple micro transducers. Approach. In this study, we developed a miniature power ultrasound transducer and used the virtual source time inversion method and 3D printing technology to design, optimize, and manufacture the acoustic holographic lens to construct a multi-target ultrasound neuromodulation system for free-moving mice. The feasibility of the system was verified by in vitro transcranial ultrasound field measurements, in vivo dual-target blood-brain barrier (BBB) opening experiments, and in vivo dual-target ultrasound neuromodulation experiments. Main results. The developed miniature transducer had a diameter of 4.0 mm, a center frequency of 1.1 MHz, and a weight of 1.25 g. The developed miniature acoustic holographic lens had a weight of 0.019 g to generate dual-focus transcranial ultrasound. The ultrasonic field measurements' results showed that the bifocal's horizontal distance was 3.0 mm, the -6 dB focal spot width in the x -direction was 2.5 and 2.25 mm, and 2.12 and 2.24 mm in the y -direction. Finally, the in vivo experimental results showed that the system could achieve dual-target BBB opening and ultrasound neuromodulation in freely-moving mice. Significance. The ultrasonic neuromodulation system based on a miniature single-element transducer and the miniature acoustic holographic lens could achieve dual-target neuromodulation in awake small animals, which is expected to be applied to the research of non-invasive dual-target ultrasonic treatment of brain diseases in awake small animals., (© 2023 IOP Publishing Ltd.)

An experiment investigated the ability by human observers to detect temporal reversals in dynamic displays of human locomotion. We video-taped the lower portion of the body of actors walking at their preferred speed either in the normal, forward direction (FW) or in the backward direction (BW). The videos were presented in a random order either as recorded (N) or in reverse (R). In one session, we presented both normal and time-reversed stimuli in the original upright orientation. In a second session, the stimuli were rotated by 180° around the horizontal axis. Observers were informed that the real recorded movement was either forward or backward and were asked to decide whether or not the movement had been time-reversed prior to the presentation. Although the kinematics of forward and backward human locomotion is quite similar, the detection of temporal reversals followed a consistent pattern showing a good accuracy in condition FW-N and a reduced but still above-chance performance in condition BW-R (by design, in both conditions actors appeared to walk forward). Performance was instead at chance level in the other two conditions where the apparent direction of the movement was backward. Inverting the spatial orientation of the stimuli reduced but did not suppress the ability to detect temporal reversals in the two conditions with apparent forward direction of movement. It is argued that implicit motor competence is at least in part instrumental for extracting the subtle discriminal information from the stimuli. [ABSTRACT FROM AUTHOR]

Abstract: The representation analysis of magnetic structures (group theory) considers generally the group (symmetry elements of the space group G which keep unchanged the propagation vector k). There exists a certain confusion about the way and the usefulness of introducing time inversion, the operation which reverses the directions of the magnetic moments. We show here that we can define two ‘time inversion’ operators, one which is linear and one which is antilinear. While introducing the linear operator does not bring any new piece of information, introducing the antilinear operator brings more details on the possible magnetic structures. Because of this antilinearity, the corepresentations have to be used instead of the usual representations. The corepresentation theory had been introduced by Wigner for the operator ‘time inversion in quantum mechanics’, operator which, in quantum mechanics, must be antilinear. Finally we show that, for magnetic structures, using an antilinear operator instead of a linear operator, is connected with the reality of the magnetic moments. To cite this article: J. Schweizer, C. R. Physique 6 (2005). [Copyright &y& Elsevier]

Rohrlich claims that “the problem of the arrow of time in classical dynamics has been solved”. The solution he proposes is based on the equations governing the motion of extended particles. Rohrlich claims that these equations, which must take self-interaction into account, are not invariant under time reversal. I dispute this claim, on several grounds. [Copyright &y& Elsevier]

We consider the case of a dynamical system when the time evolution is generated by a nonhermitian superoperator on the states of the system. Assuming the left and right eigenvectors of this to provide complete basis sets, we propose a generalized scalar product which can be used to construct a monotonically changing functional of the state, a generalized entropy. Combining the time-dependent state with its time-reversed counterpart we can define the operation of time inversion even in this case of irreversible evolution. We require that both the forward and reversed time evolution can be obtained from a generalized action principle, and this demand serves to define the form of the time-reversed state uniquely. The work thus generalizes the quantum treatment from the unitary case to the irreversible one. We present a discussion of the approach and derive some of the direct consequences of our results. [Copyright &y& Elsevier]