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.
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.
In this work we theoretically consider few variations of remarkable experiment of the single photon interference at beam splitter (without and with photon trajectories detection) where as a realistic photon trajectories detector a pair of identical simple two-level quantum systems, practically two atoms is used. Mentioned experiments (realizable by contemporary experimental techniques) clearly imply within standard quantum mechanical formalism that detectors can be microscopic, even atomic systems. Moreover, mentioned experiments admit unambiguous analysis of the existence or non-existence of the entanglement between detected quantum system (photon) and detector (pair of two-level systems) or, metaphorically speaking, Schrodinger cat effect. Since mentioned detection and entanglement existence is based at stimulated emission of the photon they can be considered as elementary form of the well-known laser technique. For this reason it can be expected that the future real experiments will confirm existence of the entanglement between photon and detector within detection procedure or non-existence of the absolute collapse.
The fully entangled Schrodinger cat state obtained immediately upon measurement of a superposed two state quantum system by a detector is often said to paradoxically predict macroscopically different outcomes simultaneously. However, nonlocal interferometry experiments and their accompanying quantum theoretical analyses, testing momentum entangled photon pairs over the full range of phases, demonstrate that the cat state does not fit this description. This state instead represents two nonlocally coherent correlations between its subsystems. Even if the detector is a cat, this state is not paradoxical. Furthermore, standard quantum theory correctly predicts the experimentally observed nonparadoxical outcomes. Thus both quantum theory and quantum experiments show there is no Schrodinger cat paradox associated with measurement. This resolves the problem of definite outcomes and, with it, the measurement problem. Upon entanglement with a detector, superpositions collapse nonlocally and unitarily to one definite macroscopic outcome. No special collapse postulate is needed.
For around five decades, physicists have been experimenting with single quanta such as single photons. Insofar as the practised ensemble reasoning has become obsolete for the interpretation of these experiments, the non-classical intrinsic probabilistic nature of quantum theory has gained increased importance. One of the most important exclusive features of quantum physics is the undeniable existence of the superposition of states, even for single quantum objects. One known example of this effect is entanglement. In this paper, two classically contradictory phenomena are combined to one single experiment. This experiment incontestably shows that a single photon incident on an optical beam splitter can either be reflected or transmitted. The almost complete absence of coincident clicks of two photodetectors demonstrates that these two output states are incompatible. However, when combining these states using two mirrors, we can observe interference patterns in the counting rate of the single photon detector. The only explanation for this is that the two incompatible output states are prepared and kept simultaneously—a typical consequence of a quantum superposition of states. (Semi-)classical physical concepts fail here, and a full quantum concept is predestined to explain the complementary experimental outcomes for the quantum optical “non-waves” called single photons. In this paper, we intend to demonstrate that a true quantum physical key experiment (“true” in the sense that it cannot be explained by any classical physical concept), when combined with full quantum reasoning (probability, superposition and interference), influences students’ readiness to use quantum elements for interpretation.
Abstract The Mach–Zehnder interferometer experiment described earlier shows why and how quantum mechanics is different from classical mechanics. A photon sent through a beam splitter behaves like a particle when it is observed by only one of the two detectors. When two beam splitters are used, the photon “interferes with itself” and behaves like a wave. This is the so-called wave-particle duality of quantum mechanics which leads to quantum entanglement. This chapter discusses quantum superpositions when two or more particles are present. Understanding and analysing entanglement is one of the most interesting directions in the field of quantum information. First, a historical background of quantum entanglement is given, followed by a discussion on Bell's inequalities, separable states that do not violate Bell's inequalities, pure states that violate Bell's inequalities, mixed states that do not violate Bell's inequalities, and entanglement in second quantisation.
This paper reviews and suggests a resolution of the problem of definite outcomes of measurement. This problem, also known as ‘Schrodinger’s cat’, has long posed an apparent paradox because the state resulting from a measurement appears to be a quantum superposition in which the detector is in two macroscopically distinct states (alive and dead in the case of the cat) simultaneously. Many alternative interpretations of the quantum mathematical formalism, and several alternative modifications of the theory, have been proposed to resolve this problem, but no consensus has formed supporting any one of them. Applying standard quantum theory to the measurement state, together with the analysis and results of decades of nonlocality experiments with pairs of entangled systems, this paper shows the entangled measurement state is not a paradoxical macroscopic superposition of states. It is instead a phase-dependent superposition of correlations between states of the subsystems. Thus Schrodinger’s cat is a non-paradoxical ‘macroscopic correlation’ in which one of the two correlated systems happens to be a detector. This insight resolves the problem of definite outcomes but it does not entirely resolve the measurement problem because the entangled state is still reversible.
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)).