In this work we consider quantum dynamical interaction of single photon with beam splitter after which well-known superposition between reflected and transmitted photon appears. Later reflected photon is absorbed by one and transmitted photon is absorbed by other, distant of two two-level systems of the same type (prepared initially in ground states). It implies entanglement between mentioned two two-level systems. Any two-level system in excited state represents an unstable system that quantum dynamically evolves in a superposition of the initial excited (non-decayed) and ground (decayed) state. We consider frequent detection at only one of two two-level systems and we prove that here a modification of the usual quantum Zeno effect called sub-systemic quantum Zeno effect appears. Namely after mentioned frequent detection two two-level systems are in a specific entangled state with two terms. First term (term of the "frozen" evolution) includes detected two-level system in initial excited state and non-detected two-level system in the ground state. Second term (term of free evolution) includes detected system in ground state and non-detected system in free evolved excited state.
In this work we consider quantum dynamical interaction of single photon with beam splitter after which well-known superposition between reflected and transmitted photon appears. Later reflected photon is absorbed by one and transmitted photon is absorbed by other, distant of two two-level systems of the same type (prepared initially in ground states). It implies entanglement between mentioned two two-level systems. Any two-level system in excited state represents an unstable system that quantum dynamically evolves in a superposition of the initial excited (non-decayed) and ground (decayed) state. We consider frequent detection at only one of two two-level systems and we prove that here a modification of the usual quantum Zeno effect called sub-systemic quantum Zeno effect appears. Namely after mentioned frequent detection two two-level systems are in a specific entangled state with two terms. First term (term of the "frozen" evolution) includes detected two-level system in initial excited state and non-detected two-level system in the ground state. Second term (term of free evolution) includes detected system in ground state and non-detected system in free evolved excited state.
In this work we theoretically consider quantum Zeno effect for entangled (correlated) quantum states. (Our physical systems and calculations are simpler than it is case in remarkable work on entanglement protection via Zeno effect by Maniscalco et all. But Maniscalco et all and our final conclusions are the same.) Firstly, we demonstrate well-known quantum Zeno effect by frequent decay detection for single, simple, two-level quantum system, with stable, ground quantum state and one non-stable, excited quantum state which can decay, by photon emission, in the ground state. (In this case, by frequent decay detections, system stands in the excited state.) Further, we consider single photon with energy equivalent to energy difference between excited and ground energy level of mentioned system. After interaction with a half-silvered mirror, mentioned photon is in a quantum superposition of the reflected and transmitted quantum state or trajectory. Mentioned trajectories are directed toward two identical, but distant, mentioned simple two-level systems both of which are initially (before interaction with photon) in ground state. Immediately after interaction with photon (photon absorption) two two-level systems are described by entangled (correlated) quantum state ( (excited, ground) + (ground, excited) , symbolically). We prove that in this case, by frequent decay detections on both systems, mentioned two two-level systems are described by initial entangled (correlated) quantum state ( (excited, ground) +(ground, excited)).
The dynamical version of the so-called ``interaction-free'' measurement [Phys. Rev. Lett. 74 (1995) 4763] is presented, in which the object called ``bomb'' is replaced with the atom evolving coherently. It is pointed out that, due to the quantum Zeno effect, the ``explosion'' symbolized by the absorption of a photon by the atom will never take place. It is shown, however, that this is accompanied by a strong modification of the involved evolution which now has a highly entangling character. Properties of the new evolution are discussed. It is also proved that beyond the quantum Zeno effect regime there is a natural possibility of conditional (i.e., followed by the sequence of some, but not necessarily frequent, probes) freezing of the evolving system in a maximally entangled state. An explanation of the effects as well as some general conclusions are provided.
In this work we suggest four simple, realistic experiments in which existence of the quantum entanglement between single photon and photon trajectory detector (Schrodinger cat effect) can be definitely testified. Mentioned experiments represent different variations of the well-known experiment of single photon interference at beam splitter. Here photon trajectory (micro) detector is represented by two simple quantum two-level systems, practically two atoms (first in excited and second in ground state) placed at only one, e.g. reflected photon trajectory. In final experiment, after first interaction between photon (in superposition state which is result of the previous, first interaction between photon and beam splitter) and detector, photon is redirected back by two total mirrors. It implies new, second interaction between photon and detector and later between photon and beam splitter. If after mentioned first interaction photon-detector entanglement exists, then after second mentioned interaction there is only one outcome at beam splitter. But if, after mentioned first interaction statistical mixture of reflected and transmitted photon exists, then after second mentioned interaction there are two outcomes at beam splitter. Results of suggested experiments can have very important role in never ending Galileian dialogue on the quantum mechanics foundation problem.
Simply speaking quantum Zeno effect for an unstable quantum system represents total decay probability decrease by frequent decay detections.Analogously simply speaking quantum anti-Zeno effect for an unstable quantum system represents total no-decay probability decrease by frequent decay detections.Also, some authors considered optical, i.e. polarization detection analogy of quantum Zeno and anti-Zeno effects.In this work we consider basic standard quantum mechanical concepts in quantum Zeno and anti-Zeno effect.We use simplest (Malus law) form of mentioned ideas on the photon polarization detection analogy of quantum Zeno and anti-Zeno effects and we suggest some new situations (non-equivalent time durations of the quantum dynamical evolutions between different frequent detections).Correspondingly we define new quantum effects, quantum Hamlet effect (when, by frequent detections, final total polarization angle and state converge but total probability for appearance of this state diverges) and quantum anti-Hamlet effect (when, by frequent detections, final total polarization angle and state diverge but total probability for appearance of this state converges).Also, we consider a rough classical mechanical analogy of Zeno effect.Finally we consider frequent interference of single photon at beam splitters and obtain for different values of reflection and transmission coefficients analogies of quantum Zeno and anti-Zeno effect as well as analogy of usual exponentially decreasing decay law.
We propose an experiment to observe the quantum Zeno effect in atomic Bragg scattering. The quantum Zeno effect is the inhibition of the free evolution of a system when that system is subject to a decohering measurement process. This effect is usually studied theoretically in an idealized two-level system, though this system has been difficult to realize in practice. The coherent population exchange between the forward and Bragg beams provides an ideal two-level system, though as there is no practical scheme for continuously monitoring the motion of an atom we include decoherence by adding noise to the laser. Using the method of stochastic Hamiltonians we show that the noise suppresses tunneling in the two-state system and, in the large noise limit, the system can freeze in its initial state.
A discussion of the quantum Zeno effect and paradox is given. The quantum Zeno paradox claims that a continuously observed system, prepared in a state which is not an eigenstate of the Hamiltonian operator, never decays. To recover the classical behavior of unstable systems we consider a two-level system interacting with a Bose field, respectively prepared in the excited state and in the Poincare invariant vacuum state. Using time-dependent perturbation theory, we evaluate for a finite time interval the probability of spontaneous decay of the two-level system. Using the standard argument to obtain the quantum Zeno paradox, we consider N measurements where N goes to infinity and we obtain that the non-decay probability law is a pure exponential, therefore recovering the classical behavior.