Abstract—Decoherence is considered as one of the important topics in quantum computing research area. Some researchers stated that decoherence solved the measurement problem and on the other hand many researchers stated the opposite. In this paper we will prove whether decoherence is a solution or not through an exhaustive survey of the different ideas, methodologies, and experiments. Index Terms—Quantum computing, decoherence, measurement problem INTRODUCTION Decoherence is considered as one of the important research areas since 1980s.
Quantum decoherence is the Loss of coherence or ordering of the phase angles between the components of a system in quantum computing superposition and the consequence of this is classical or probabilistically additive behavior... (Zurek Today 10 (1991)) Wave function collapse is the reduction of the physical possibilities into a single possibility as seen by observer can appear in quantum decoherence also it justifies the framework and can predict using classical physics as an acceptable approximation... Namiki and Pascazio 1991). However, decoherence is a mechanism that emerges out quantum stating point also it determines the location of the quantum classical boundary moreover decoherence appear when the quantum system interacts with its environment in a thermodynamically irreversible way and that lead to prevent different factors in the quantum superposition of the system and environments wave function from interfering with each other... Zurek Today 10 (1991)) Decoherence can be viewed in different ways such as flowing information from the system to the environment lead to lose information this is known as heat bath since each system is losing some of its energetic state because of its surroundings environments... (Kumar, Kiranagi et al. 012) There is also another view of decoherence that is called isolation; which is the combination of the system and the environment which known as non-unitary therefore the dynamics of the system alone are irreversible also as a result of combination of system and environment the entanglements are generated between them and that will lead to sharing quantum information without transferring these information to the surroundings… (Lidar and Whaley 2003) Describing how the wave function collaps occurs in quantum mechanics called measurement problem. The disability of observing the process directly lead to different nterpretations regard quantum mechanics, also it rises too many qustions that each interpretation must answer. However there are some researches provides aprove that the decoherence solved the measurment problem and some other researchers prove the opposite thus in this paper we will make a comparasion between these two different point of views… (Kumar, Kiranagi et al. 2012) PROBLEM IDENTIFICATION Decoherence is a real challenge that prevents implementing quantum computers; because the machines rely on undisturbed evolution of quantum coherences… (Chen, Ang et al. 003), (Flitney and Abbott 2004) Decoherence provides an explanations for the appearance of the wave function collapse it does not generate actual wave function collapse and that is the nature of quantum systems it leaks into the environment and that done by decomposing the component of the wave function from the coherent system and then applying phases to the environment…(Flitney and Abbott 2004) P. W Anderson claimed that decoherence has solved the Quantum measurement problem while S. L Adler prove the opposite…. Adler 2002) In this paper, we will conduct a comprehensive survey of the different views and experiments to come up with a solution for the relationship between decoherence and measurement problem. Decoherence is the Solution Zurek (1991), Tegmark and Wheeler (2001), and Anderson (2001) stated that decoherence has solved the quantum measurement problem by eliminating the necessity for Von Neumann’s wave function collapse postulate. Osvaldo Pessoa Jr. wrote an article titled “Can the Decoherence Approach Help to Solve the Measurement Problem? He concluded that decoherence could help to solve measurement problem in open systems. From that point, he wanted to count on the open systems to solve the measurement problem of individual systems. He also mentioned that decoherence helps to get an approximate solution for the statistical version of the measurement problem. Wallace (2011) mentioned that decoherence explains why the measurement problem is a philosophical rather than a practical problem and stated that decoherence could solve the measurement problem.
He claimed that the quantum state continues to describe the physical state of the world. So, decoherence finds its natural role in the measurement problem as the process which explains why quantum mechanics can be fundamentally deterministic and non-classical, but emergently classical. It does not dull the aspect of Everett's proposal, which states that all are equally part of the underlying quantum reality. Decoherence is Not the Solution
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The decoherence initiative was to explain the transformation from large to conventional by evaluating the relationships of a program with a determining program or with the environment. It is realistic to think about a large specialized substance or program of pollutants as a divided program boating in unfilled space. Dynamical Failing Styles Somehow do not like the idea of failure due to professionals trying to rig the pattern function improvement so to advantage loss of the situation vector in a well described way.
One way is to say that the pattern function, or at least an element of it, consistently gets “hit” in such a way as to cause localization in the position base. Another way is to add a not unitary term into Schrodinger’s program. There are suggestions stated that we can infer using mind ability to get the collapse of the wave function Tohmas Breuer at 1996 try to investigate these suggestions and apply it to recent results of quantum machines regard restrictions on measurement from inside.
Tohmas Breuer count on these restrictions to come up with a phenomena of subjective decoherence therefore he split his article into parts. The first part is “measurement from inside” and he makes a presentation to illustrate why it is impossible for an observer to make a distinction between all states in a system in which an observer is contained and that consider as restriction on the measurability from inside, he conclude that bigger system O need more parameters to fix its state.
However, this will lead to situations that big O can be determined of each physically possible state by the state of a subsystem A together with some constraint. Second part is “EPR-Correlations” and he focus on situation which stronger results hold when we take into account particular features of quantum mechanical situations for example if we have two systems A and some environment R then the union of two system A ? R equal to Big O. also if both systems A and R have Hilbert spaces HA and HR as state spaces then EPR correlations can be obtained in the vector states ?? HA HR .
Therefore he conclude that A con not make a distinction between states of O which is make difference only in the EPR correlations between A and R. however observers can only be able to make a measurement of EPR correlations between A and R in A ? R…(Breuer 1996) David Wallace wrote his article to achieve two goals the first one is to present an account of how quantum measurements are dealing with in modern physics in other word quantum measurements does not involve a collapse of the wave functions also to present the measurement problem from that account perspective of view.
The second part is concentrate on clarifying the role of decoherence plays in modern measurement theory and what affects it has on the different strategies that have been proposed to solve measurement problem. Wallace concluded that it seems not possible to have a complete understating of the microscopic predictions quantum mechanisms without interpreting the state in a probabilistic way and that because of interference since quantum states cannot be thought of as probability distributions in physical states of airs.
Therefore it is allowable to try to resolve the incoherence by two ways, the first one by philosophical methods which means trying hard to think about how to make a full understanding quantum states so as to come out with a non-incoherent way, also the second way done by making modifications on the physics which means trying to make a replacement of the quantum mechanics by using some new theory which does not prima facie lead to the conceptual incoherence.
Finally, Wallace state that the natural role of decoherence can be found in the measurement problem as the process which provides an explanations regard why quantum mechanics, interpreted can be basically not classical and deterministic, but critically classical…(Wallace 2011) Dan Stahlke based on application he made state that the most important point of decoherence theory is that it provides understanding about the process of wave collapse. Some systems need to be built in way that it stays in coherent superposition.
However, tendency of system that been in superposition can be immediately calculated. Also he stated that decoherence does not give the ultimate solution in the measurement problem but it bring some light to the matter…(Stahlke 1999) Maximilian Schlosshauer makes a distinctive discussion regard the role of decoherence in the foundation of quantum mechanics, and focusing of the effectiveness of decoherence regard the measurement problem. He concludes that within a standard interpretation of quantum mechanics that decoherence cannot solve the problem of definite outcomes in quantum measurement.
Therefore he mention the effectiveness of environment super selection of quasiclassical pointer states along with the local superposition of interference terms can be put to large use in physical motivation, assumptions and rules regard alternative interpretation approaches that can change the strict orthodox eigenvalue-eigenstate link or make modification on the unitary dynamics to account for the awareness of definite outcomes…(Schlosshauer 2005) Elise M.
Crull mention in his article that it has been claimed that decoherence has solved the measurement problem. In other hand, some researchers stated that it does not solve the measurement problem. However, the Crull target is “Which measurement problem? ”, thus he argue three questions depending on Max Schlosshauer which has neat catalog on the different problems which called “the measurement problem”…(Schlosshauer 2008; Crull 2011) Harvey Brown stated that there are many attempts to proof the insolubility of the measurement problem in non-quantum mechanics.
We can use these attempts for quantum mechanics. These proofs tend to establish that if mechanical interaction between object system A and measuring instrument B is described through a suitable defined unitary operator on the “Hilbert” tensor product space, so the final state of the A + B together cannot be described by a density operator of a specific kind in that space.
Therefore this leads us to a resolution in terms of weighted projections which be useful to interpreted as mixture of pure A + B states, which are eigenstates corresponding to the “pointer position” that observable connected with the instrument…(Brown 1986) Ford, Lewis and Connell count on a book “Decoherence and the Appearance of a Classical World in Quantum Theory” …(Giulini, Joos et al. 1996) which state that ‘‘irreversible coupling to the environment seems to have become widely accepted ~and even quite popular!
During the last decade, not least through the various contributions by Woljciech Zurek and his collaborators. ’’ And he conclude that general and simple formulation of quantum measurement gives a good method regard discussing quantum stochastic systems…(Ford and Lewis 1986) . Also authors stated that decoherence appear at high temperature with or without dissipation and the time for both cases are the same furthermore at zero temperature, decoherence occurs only in the presence of dissipation…(Ford, Lewis et al. 001) In 1980s and 1990s techniques are established to cool single ions captured through a trap and to control their state by using laser light and the single ion can be observed using photons with minimal interaction with the environment. Photons can observed without being destroyed during interaction together with atoms in designed experiment. That leads to make a study regard pioneers that make a test for basis of quantum mechanics also the transition between microscopic and microscopic world.
The most important stage in controlling the quantum state regard ion is cooling it to the lowest energy of the trap using a common technique called sideband cooling…(F. Diedrich, Bergqvist et al. 1989) this technique consists of exiting the ion, increasing inside energy also decreasing the vibration energy…(SCIENCES 2012) Bas Hensen starting his discussion by defining the measurement problem and he stated that measuemet problem begin naturally from quantum theory’s success through describing the realm regard microscopic particles also permitting them to have definite values for quantities like momentum and position.
Then he split the problem into several parts. The first two parts are “the problem of outcomes: Why does one perceive a single outcome among the many possible ones in equation? ”, “The problem of the collapse: What kind of process causes the state of the system to ‘collapse’ to the outcome one perceived (in the sense that a repeated measurement yields the same answer)? ” in these two part he found that in quantum the world must be divided into a wave quantum system and the rest stays in some classical system.
Also in accuracy point of view the division is made one way or another in a particular application. The third part is “The problem of interference: Why do we not observe quantum interference effects on macroscopic scales? ” in this part author stated that the best way to illustrate this problem by using the double slit experiment. The experiment shows that the physical setup suggests that grouping the probability distribution gained with either one of the slit opened should occur in the probability distribution regard the two slits opened.
For this situation of electrons as particles the probability distribution regard course differs, but regard a similar setup using macroscopic particles it doesn’t…(Hensen 2010 ) Dieks reviewed several proposals that solved the quantum mechanical measurement problem by taking into account that in measurement interactions there are many unobserved degrees of freedom. He found out that such “solutions” are unsatisfactory as they stand, and must be supplemented by a new empirical interpretation of the formal state description of quantum mechanics (Dieks 1989).
Zurek mentioned in " Decoherence, Einselection, and the Quantum Origins of the Classical" that decoherence is caused by the interaction in which the environment in effect monitors certain observables of the system, destroying coherence between the pointer states corresponding to their eigenvalues. Then, he mentioned that when the measured quantum system is microscopic and isolated, this restriction on the predictive utility of its correlations with the macroscopic apparatus results in the effective “collapse of the wave packet”; which implicitly states that decoherence did not solve the measurement problem (Zurek 2003).
Elby scrutinized the claim that the measurement problem is solved by decoherence, by examining how modal and relative-state interpretations can use decoherence. He mentioned also that although decoherence cannot rescue these interpretations from general metaphysical difficulties, decoherence may help these interpretations to pick out a preferred basis (Elby 1994). Janssen mentioned that the alleged relevance of decoherence for a solution of the "measurement problem" is subjected to a detailed philosophical analysis.
He reconstructed a non-standard decoherence argument that aimed to uncover some hidden assumptions underlying the approach. He concluded that decoherence cannot address the "preferred-basis problem" without adding new interpretational axioms to the standard formalism (Janssen 2008). Busch et al (1996) explained decoherence using the many-worlds interpretation and stated the decoherence cannot solve the measurement problem. Leggett (2005) concentrated on the paradox of Schrodinger's cat or the quantum measurement paradox to prove that dechorence is not a practical solution.
Other researchers and scientists including Gamibini and Pullin (2007), Zurek (2002), Joos and Zeh (1985), Bell (1990), Albert (1992), Bub(1997), Barrett (1999), Joos (1999), and Adler (2002) stated that decoherence did not solve the measurement problem. Conclusion There is a serious and unresolved quantum measurement problem. Some, like Ghirardi, Rimini, and Weber (1986), try to solve it by modifying quantum mechanics. If successful, such attempts would result in a theory, distinct from but closely related to quantum mechanics, that is no longer subject to a measurement problem. That problem may be unsolvable (Healey 1998).
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