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A strategy is developed for writing the time-dependent Schrödinger Equation (TDSE), and more generally the Dyson Series, as a convolution equation using recursive Fourier transforms, thereby decoupling the second-order integral from the first without using the time ordering operator. The energy distribution is calculated for a number of standard perturbation theory examples at first- and second-order. Possible applications include characterization of photonic spectra for bosonic sampling and four-wave mixing in quantum computation and Bardeen tunneling amplitude in quantum mechanics. [ABSTRACT FROM AUTHOR]

For a three-level system monitored by an ancilla, we show that the quantum Zeno effect can be employed to control quantum jump for error correction. Further, we show that we can realize cNOT gate, and effect dense coding and teleportation using a three-level system with an ancilla. We believe that this work paves the way to generalize the control of a qudit. [ABSTRACT FROM AUTHOR]

The Elitzur-Vaidman bomb testing problem is a thought experiment in quantum mechanics that explores the concepts of quantum superposition and entanglement. The problem creates a scenario where a bomb is activated by absorbing a single photon and suggests testing that it works without exploding it, so that classically, it is impossible to know if the bomb works without disturbing the system. Therefore, an interferometer with two arms and two outputs is proposed, mounted in such a way that only one of them has positive interference. However, when placing a pump that works in one of the arms, the interference pattern breaks down, and it can be inferred that the pump works without interacting with it. In this work, a methodology is adopted that combines computational simulations and a simple experimental proposal to investigate the concept of interaction-free measurements. The IBM quantum cloud programming language (Qiskit Runtime) is utilized to simulate the experiments, and an experimental approach is proposed that uses simple laser sources to qualitatively test the theory, offering a practical perspective for developing an understanding of quantum concepts. [ABSTRACT FROM AUTHOR]

Classical measurements are passive, in the sense that they do not affect the physical properties of the measured system. Normally, quantum measurements are not passive in that sense. In the infinite dimensional Hilbert space, however, it is found that quantum projective measurement can be passive in a way which is impossible in finite dimensional Hilbert spaces. Specifically, it is found that expectation value of a hermitian Hamiltonian can have an imaginary part in the infinite dimensional Hilbert space and that such an imaginary part implies a possibility to avoid quantum Zeno effect, which can physically be realized in quantum arrival experiments. The avoidance of quantum Zeno effect can also be understood as avoidance of a quantum version of gambler's fallacy, leading to the notion of passive quantum measurement that updates information about the physical system without affecting its physical properties. The arrival time probability distribution of a particle is found to be given by the flux of the probability current. Possible negative fluxes correspond to regimes at which there is no arrival at all, physically understood as regimes at which the particle departs rather than arrives. [ABSTRACT FROM AUTHOR]

The Stimulated Raman Adiabatic Passage, a very efficient technique for manipulating a quantum system based on the adiabatic theorem, is analyzed in the case where the manipulated physical system is interacting with a spin bath. The exploitation of the rotating wave approximation allows for the identification of a constant of motion, which simplifies both the analytical and the numerical treatment, which allows for evaluating the total unitary evolution of the system and bath. The efficiency of the population transfer process is investigated in several regimes, including the weak and strong coupling with the environment and the off-resonance. The formation of appropriate Zeno subspaces explains the lowering of the efficiency in the strong damping regime. [ABSTRACT FROM AUTHOR]

The effect of the presence of two probe waveguides on the dynamics of hyper‐Raman processes is studied in terms of quantum Zeno and anti‐Zeno effects. Specifically, the enhancement (diminution) of the evolution of the hyper‐Raman processes due to interaction with the probe waveguides via evanescent waves is viewed as quantum Zeno (anti‐Zeno) effect. This study considers the two probe waveguides interacting with only one of the optical modes at a time. For instance, as a specific scenario, it is considered that the two non‐degenerate pump modes interact with each probe waveguide linearly, while Stokes and anti‐Stokes modes do not interact with the probes. Similarly, in another scenario, it is assumed both the probe waveguides interact with Stokes (anti‐Stokes) mode simultaneously. The present results show that quantum Zeno (anti‐Zeno) effect is associated with phase‐matching (mismatching). However, it do not find any relation between the presence of the quantum Zeno effect and antibunching in the bosonic modes present in the hyper‐Raman processes. [ABSTRACT FROM AUTHOR]

The Stimulated Raman Adiabatic Passage, a very efficient technique for manipulating a quantum system based on the adiabatic theorem, is analyzed in the case where the manipulated physical system is interacting with a spin bath. The exploitation of the rotating wave approximation allows for the identification of a constant of motion, which simplifies both the analytical and the numerical treatment, which allows for evaluating the total unitary evolution of the system and bath. The efficiency of the population transfer process is investigated in several regimes, including the weak and strong coupling with the environment and the off-resonance. The formation of appropriate Zeno subspaces explains the lowering of the efficiency in the strong damping regime.

The Copenhagen interpretation of quantum mechanics contains a fundamental refuse to visualize quantum processes, so as not to conflict with common sense. The lack of visualization creates a problem in understanding quantum mechanics. We are exploring a new type of motion, which has not been previously considered either in physics or in mathematics. This type of motion makes it possible to correctly describe and visualize the bizarre quantum processes, including quantum jumps, nonlocality, quantum entanglement, wave-particle duality, and so on. We also made some simple figures of these quantum processes using a new type of movement. Visualization of quantum processes will help to better understand quantum mechanics not only for researchers and students but also for lay readers interested in quantum physics. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai University / Shanghai Daxue Xuebao is the property of Journal of Shanghai University (Natural Sciences) Editorial Office 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.)

On a quantum superconducting processor we observe partial and infinite-temperature thermalization induced by a sequence of repeated quantum projective measurements, interspersed by a unitary (Hamiltonian) evolution. Specifically, on a qubit and two-qubit systems, we test the state convergence of a monitored quantum system in the limit of a large number of quantum measurements, depending on the non-commutativity of the Hamiltonian and the measurement observable. When the Hamiltonian and observable do not commute, the convergence is uniform towards the infinite-temperature state. Conversely, whenever the two operators have one or more eigenvectors in common in their spectral decomposition, the state of the monitored system converges differently in the subspaces spanned by the measurement observable eigenstates. As a result, we show that the convergence does not tend to a completely mixed (infinite-temperature) state, but to a block-diagonal state in the observable basis, with a finite effective temperature in each measurement subspace. Finally, we quantify the effects of the quantum hardware noise on the data by modelling them by means of depolarizing quantum channels.

Periodic deterministic bang–bang dynamical decoupling and the quantum Zeno effect are known to emerge from the same physical mechanism. Both concepts are based on cycles of strong and frequent kicks provoking a subdivision of the Hilbert space into independent subspaces. However, previous unification results do not capture the case of random bang–bang dynamical decoupling, which can be advantageous to the deterministic case but has an inherently acyclic structure. Here, we establish a correspondence between random dynamical decoupling and the quantum Zeno effect by investigating the average over random decoupling evolutions. This protocol is a manifestation of the quantum Zeno dynamics and leads to a unitary bath evolution. By providing a framework that we call equitability of system and bath , we show that the system dynamics under random dynamical decoupling converges to a unitary with a decoupling error that characteristically depends on the convergence speed of the Zeno limit. This reveals a unification of the random dynamical decoupling and the quantum Zeno effect.

Abstract The Bell-state analysis to distinguish between the four maximally entangled Bell states requires the joint measurement on entangled particles. However, spatially separated parties cannot perform the joint measurement. In this paper, we present a counterfactual Bell-state analysis based on the chained quantum Zeno effect. This counterfactual analysis not only enables us to perform a complete Bell-state analysis, but also enables spatially separated parties to distinguish between the four Bell states without transmitting any physical particle over the channel.

In recent years, remarkable progress has been achieved in the development of quantum computers. For further development, it is important to clarify properties of errors by quantum noise and environment noise. However, when the system scale of quantum processors is expanded, it has been pointed out that a new type of quantum error, such as nonlinear error, appears. It is not clear how to handle such new effects in information theory. First of all, one should make the characteristics of the error probability of qubits clear as communication channel error models in information theory. The purpose of this paper is to survey the progress for modeling the quantum noise effects that information theorists are likely to face in the future, to cope with such nontrivial errors mentioned above. This paper explains a channel error model to represent strange properties of error probability due to new quantum noise. By this model, specific examples on the features of error probability caused by, for example, quantum recurrence effects, collective relaxation, and external force, are given. As a result, it is possible to understand the meaning of strange features of error probability that do not exist in classical information theory without going through complex physical phenomena.

Consecutive measurements performed on the same quantum system can reveal fundamental insights into quantum theory's causal structure, and probe different aspects of the quantum measurement problem. According to the Copenhagen interpretation, measurements affect the quantum system in such a way that the quantum superposition collapses after each measurement, erasing any memory of the prior state. We show here that counter to this view, un-amplified measurements (measurements where all variables comprising a pointer are in principle controllable) have coherent ancilla density matrices that encode the memory of the entire set of (un-amplified) quantum measurements that came before, and that the chain of this entire set is therefore non-Markovian. In contrast, sequences of amplified measurements (measurements where at least one pointer variable has been lost) are equivalent to a quantum Markov chain. We argue that the non-Markovian nature of quantum measurement has empirical consequences that are incompatible with the assumption of wave function collapse, thus elevating the collapse assumption into a testable hypothesis. Finally, we find that all of the information necessary to reconstruct an arbitrary non-Markovian quantum chain of measurements is encoded on the boundary of that chain (the first and the final measurement), reminiscent of the holographic principle. [ABSTRACT FROM AUTHOR]

A scheme is proposed to estimate the decay rates of the subsystem in an atom–cavity-optomechanical system which also is known as the hybrid optomechanical system. Quantum Fisher information and quantum Zeno effect (QZE) are investigated under different conditions. The results show that the estimation precision of the decay rates can reach 9.64 × 10 - 6 , 3.49 × 10 - 4 and 7.91 × 10 - 5 , respectively. The Zeno–anti-Zeno crossover can be realized in the hybrid optomechanical system. We find that both QZE and quantum anti-Zeno effect (QAZE) are always beneficial to the estimation of the mechanical oscillator decay rate. However, when the cavity decay rate is estimated, QAZE may enhance or inhibit the estimation precision at the different time regions. The results provide some potential applications in quantum networks and quantum Zeno switch. [ABSTRACT FROM AUTHOR]

Copyright of International Dialogue: East-West is the property of International Center for Slavic Education- Sveti Nikole 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.)

In this paper, we discuss approximations of the dynamical quantum Zeno effect by a fixed number of nonselective quantum measurements. A wide class of measurements whose efficiency is close to optimal in the case of two-level systems is found. [ABSTRACT FROM AUTHOR]

The fundamental law of parsimony in science, which is colloquially referred to as Occam's razor, gives precedence to simplicity in the development of a theory. We wish to illustrate this principle by revisiting the issue related to the long-lasting continuous experimental measurement of a Rabi-driven qubit (Minev et al., 2019). We propose a simple and basic explanation of the results that proceeds from the variance property of the Hamiltonian in the case of a weak Rabi drive. This variance provides a large statistical time-dependent range of available values for the qubit energy (namely, its standard deviation) that spreads out about Rabi's well-known harmonic state-flipping mean value. In the presence of a long-lasting continuous measurement process like in Minev et al experiment, the resulting "quantum Zeno freezing" of the observed system keeps its energy frozen in its initial state as long as this remains possible within the standard deviation of the energy. Otherwise the system suddenly experiences a quantum jump between the two energy levels – dubbed a quantum Zeno jump – in order to resume its state-freezing dynamics. Some link is made with the dynamics of swapping gates in quantum information processing. • This work stresses the generic importance of the competition between Quantum-Zeno freezing vs Rabi flipping in harmonically driven and continuously observed two-level quantum systems. • Due to their variance properties, this competition yields sudden quantum transitions dubbed quantum Zeno jumps. • These latter have been observed by Minev et al (2019). [ABSTRACT FROM AUTHOR]

It is known that, in quantum theory, measurements may suppress Hamiltonian dynamics of a system. A famous example is the ‘Quantum Zeno Effect’. This is the phenomena that, if one performs the measurements M times asking whether the system is in the same state as the one at the initial time until the fixed measurement time t, then survival probability tends to 1 by taking the limit M→∞. This is the case for fixed measurement time t. It is known that, if one takes measurement time infinite at appropriate scaling, the ‘Quantum Zeno Effect’ does not occur and the effect of Hamiltonian dynamics emerges. In the present paper, we consider the long time repeated measurements and the dynamics of quantum many body systems in the scaling where the effect of measurements and dynamics are balanced. We show that the stochastic process, called the symmetric simple exclusion process (SSEP), is obtained from the repeated and long time measurements of configuration of particles in finite lattice fermion systems. The emerging stochastic process is independent of potential and interaction of the underlying Hamiltonian of the system.

The counterpart of the rotating wave approximation for non-Hermitian Hamiltonians is considered, which allows for the derivation of a suitable effective Hamiltonian for systems with some states undergoing decay. In the limit of very high decay rates, on the basis of this effective description we can predict the occurrence of a quantum Zeno dynamics, which is interpreted as the removal of some coupling terms and the vanishing of an operatorial pseudo-Lamb shift.

The effective lifetime of a quantum state can increase (the quantum Zeno effect) or decrease (the quantum anti-Zeno effect) in the response to increasing frequency of the repeated measurements and the multiple transitions between these two regimes are potentially possible within the same system. An interesting question arising in this regards is how to choose the optimal schedule of repeated measurements to achieve the maximal possible decay rate of a given quantum state. Addressing the issue of optimality in the quantum Zeno dynamics, we derive a range of rigorous results, which are, due to generality of the theoretical framework adopted here, applicable to the majority of models appeared in the quantum Zeno literature. In particular, we prove the universal dominance of the regular stroboscopic sampling in the sense that it always provides the shortest expected decay time among all possible measurement procedures. However, the implementation of the stroboscopic protocol requires the knowledge of the optimal sampling period which may depend on the fine details of the quantum problem. We demonstrate that this difficulty can be overcome with the tricky non-regular measurement schedule inspired by the scale-free restart strategy used to speed up the completion of the probabilistic algorithms and Internet tasks in computer science as it allows to achieve a near-optimal decay rate in the absence of detailed knowledge of the underlying quantum statistics. Besides, our general approach reveals unexpected universality displayed by the quantum systems subject to the optimally tuned rate of Poissonian measurements and the simple statistical criteria to discriminate between Zeno and anti-Zeno regimes following from this universality. We illustrate our findings with an example of Zeno dynamics in the system of optically-trapped ultra-cold atoms and discuss the implications arising from them.

Abstract We analyze the quantum Zeno and anti-Zeno effect in a spin–spin model, where a two-level system is embedded in a sea of spins with nonuniform couplings. By employing a generalized polaron transformation as well as a perturbative approach, the analytical expression of the effective decay rate of the spin–spin model is obtained. Compared with the well-known spin-boson model, we show that the two models share the same short-time dynamical behavior if and only if the environmental temperature is zero. We also find that the effective decay rate in the spin environment is larger than that of the harmonic environment for the sub-Ohmic spectrum case. Moreover, it is demonstrated that the crossover between quantum Zeno effect and anti-Zeno effect is highly sensitive to the details of the bath spectral function regardless of the spin environment or the harmonic environment. [ABSTRACT FROM AUTHOR]

We describe a chain of quantum oscillators which behaves analogously to Newton's cradle. The energy swings between the ends of the chain with very low population in its interior. Moreover, the oscillators at the ends can entangle with each other with negligible entanglement with the intermediate oscillators that mediate the process. Up to a certain number of oscillators, the system evolves in a manner similar to two coupled oscillators. The conditions for such behavior and the characteristic periods are analyzed. When that number exceeds a threshold, the dynamical regime changes to virtually freezing. In the oscillatory regime, Zeno effect can be observed. The parallelism between the Zeno dynamics in quantum Newton's cradle and in two coupled oscillators is highlighted. Promising platforms to observe such phenomena in the laboratory are cavities in photonic-band-gap material and trapped ions. [ABSTRACT FROM AUTHOR]

As science reaches further into the cognitive domain, questions once thought firmly outside the realm of science are becoming subjects of scientific inquiry. One of the foremost challenges is the relationship of our thoughts and intentions to the world we study and manipulate. Once thought intractable, this problem seems newly open to scientific discovery. Neurological correlates of many cognitive functions are being discovered, yielding advances in medicine and education. The growth of artificial intelligence raises the possibility that intelligent behavior can be understood scientifically, formalized, and engineered into intelligent devices. Yet the problem of free will eludes our grasp. We have the distinct sense that we make choices, and those choices have effects. The world is different from what it would have been had we chosen otherwise. But could we really have chosen otherwise, or are the choices we make determined by the electrochemistry of our brains? This paper examines a proposed theory of a physical basis for efficacious free choice, and asks whether it can be operationalized as a concrete, falsifiable model. The hypothesized mechanism involves automatic generation by the brain of templates for action, which are held in place by rapidly repeated quantum self-measurement events. A computer simulation of this model could support investigation of whether, using biologically plausible parameter settings, the hypothesized mechanism can produce macroscopic behavioral effects. Ultimately, such investigations could lead to empirical tests of the theory. [ABSTRACT FROM AUTHOR]

A Gedanken experiment is presented where an excited and a ground-state atom are positioned such that, within the former's half-life time, they exchange a photon with 50% probability. A measurement of their energy state will therefore indicate in 50% of the cases that no photon was exchanged. Yet other measurements would reveal that, by the mere possibility of exchange, the two atoms have become entangled. Consequently, the 'no exchange' result, apparently precluding entanglement, is non-locally established between the atoms by this very entanglement. This quantum-mechanical version of the ancient Liar Paradox can be realized with already existing transmission schemes, with the addition of Bell's theorem applied to the no-exchange cases. Under appropriate probabilities, the initially-excited atom, still excited, can be entangled with additional atoms time and again, or alternatively, exert multipartite nonlocal correlations in an interaction free manner. When densely repeated several times, this result also gives rise to the Quantum Zeno effect, again exerted between distant atoms without photon exchange. We discuss these experiments as variants of interaction-free-measurement, now generalized for both spatial and temporal uncertainties. We next employ weak measurements for elucidating the paradox. Interpretational issues are discussed in the conclusion, and a resolution is offered within the Two-State Vector Formalism and its new Heisenberg framework. [ABSTRACT FROM AUTHOR]

We consider two alternative procedures which can be used to control the evolution of a generic finite-dimensional quantum system, one hinging upon a strong continuous coupling with a control potential and the other based on the application of frequently repeated pulses onto the system. Despite the practical and conceptual difference between them, they lead to the same dynamics, characterised by a partitioning of the Hilbert space into sectors among which transitions are inhibited by dynamical superselection rules.

Intuition from our everyday lives gives rise to the belief that information exchanged between remote parties is carried by physical particles. Surprisingly, in a recent theoretical study [Salih H, Li ZH, Al-Amri M, Zubairy MS (2013) Phys Rev Lett 110:170502], quantum mechanics was found to allow for communication, even without the actual transmission of physical particles. From the viewpoint of communication, this mystery stems from a (nonintuitive) fundamental concept in quantum mechanics—wave-particle duality. All particles can be described fully by wave functions. To determine whether light appears in a channel, one refers to the amplitude of its wave function. However, in counterfactual communication, information is carried by the phase part of the wave function. Using a single-photon source, we experimentally demonstrate the counterfactual communication and successfully transfer a monochrome bitmap from one location to another by using a nested version of the quantum Zeno effect. [ABSTRACT FROM AUTHOR]

We study the entanglement protection between two identical qubits interacting with independent zero-temperature reservoir beyond the Born-Markoivan approximation. The principle is based on an analog of a zero-ground quantum screening method in an electronic circuit, it employs an auxiliary casing system to erase the excited state to the ground state frequently to inhibit the decoherence. We find that the auxiliary casing system plays a crucial role and the number of screening events is proportional to the entanglement protection, the physical mechanism is also given in the context. [ABSTRACT FROM AUTHOR]

We propose a scheme to realize the quantum state transfer (QST) and conditional phase gate (CPG) between two qubits (acted by nitrogen-vacancy (NV) centers) based on off-resonant quantum Zeno dynamics. We also consider the entanglement dynamics of two qubits in this system. Since no cavity photons or excited levels of the NV center is populated during the whole process, the scheme is immune to the decay of cavity and spontaneous emission of the NV center. The strictly numerical simulation shows that the fidelities of QST and CPG are high even in the presence of realistic imperfections. [ABSTRACT FROM AUTHOR]