Introduction In this chapter, we discuss some of the differences between apparatus and systems under observation (SUOs). The discussion is phrased in terms of self–intervening networks , wherein partial quantum outcomes in an early stage of an apparatus can alter future configurations of that apparatus. To explain what we mean, we introduce the following classification of experiments. Note that reference to apparatus here includes real and virtual detectors, and real and virtual modules. Virtual detectors and modules are mathematical fictions that are introduced into the formalism for convenience. Type-Zero Experiments Many important experiments involve signal propagation through “empty space.” We classify these as type zero (T0). The feature of T0 experiments qualifying for this classification is that the observer has no control of the modules in the information void. Examples are experiments in astrophysics, where the observer can choose which source to observe and how they observe it, but has no influence on the physical properties of whatever lies between source and detector. If there are gas clouds between source and detector, the observer can only recognize that fact after the experimental data are analyzed. An important modern variant of T0 experiments involves map location via the Global Positioning System (GPS): signals sent from Earth to geostationary satellites and received by mobile devices back on Earth have traveled through Earth's atmosphere and through empty space, where special relativistic and general relativistic effects have to be taken into account (Ashby, 2002). Before the rise of experimental science, most “experiments” were based on visual observations, which are principally of T0 classification. The advent of the telescope and the microscope did not change things in this respect. Indeed, it has been suggested that science did not progress in antiquity precisely because of the philosophical principle that the only valid experiments could be of T0, as these do not introduce the artificiality of constructed modules into observation, which (it was argued) would give a false perspective on “reality.” The logic of that argument is superb, but it is a dead-end principle in science. Several sciences such as geology, archaeology, and, indeed, cosmology started off with periods of basic observation rather than experimentation. During such initial stages of these sciences, the observations could be classified as T0 experiments.
Introduction In this chapter, we discuss some of the differences between apparatus and systems under observation (SUOs). The discussion is phrased in terms of self–intervening networks , wherein partial quantum outcomes in an early stage of an apparatus can alter future configurations of that apparatus. To explain what we mean, we introduce the following classification of experiments. Note that reference to apparatus here includes real and virtual detectors, and real and virtual modules. Virtual detectors and modules are mathematical fictions that are introduced into the formalism for convenience. Type-Zero Experiments Many important experiments involve signal propagation through “empty space.” We classify these as type zero (T0). The feature of T0 experiments qualifying for this classification is that the observer has no control of the modules in the information void. Examples are experiments in astrophysics, where the observer can choose which source to observe and how they observe it, but has no influence on the physical properties of whatever lies between source and detector. If there are gas clouds between source and detector, the observer can only recognize that fact after the experimental data are analyzed. An important modern variant of T0 experiments involves map location via the Global Positioning System (GPS): signals sent from Earth to geostationary satellites and received by mobile devices back on Earth have traveled through Earth's atmosphere and through empty space, where special relativistic and general relativistic effects have to be taken into account (Ashby, 2002). Before the rise of experimental science, most “experiments” were based on visual observations, which are principally of T0 classification. The advent of the telescope and the microscope did not change things in this respect. Indeed, it has been suggested that science did not progress in antiquity precisely because of the philosophical principle that the only valid experiments could be of T0, as these do not introduce the artificiality of constructed modules into observation, which (it was argued) would give a false perspective on “reality.” The logic of that argument is superb, but it is a dead-end principle in science. Several sciences such as geology, archaeology, and, indeed, cosmology started off with periods of basic observation rather than experimentation. During such initial stages of these sciences, the observations could be classified as T0 experiments.
Introduction In this chapter we discuss how quantized detector network (QDN) theory can be extended to cover the creation and decommissioning of apparatus, from the perspective of observers and their laboratories. This extension will be referred to as extended QDN. It allows us to discuss bit power sets, laboratories, the universal register, contextual vacua, and the creation of quantized detector apparatus. This extended formalism is used to describe the Elitzur–Vaidman bomb-tester experiment and the Hardy paradox experiment. A central concept running through this book is that of the observer , the enigmatic “ I ” of I think therefore I am . The problem is that, despite the many triumphs of quantum mechanics (QM), the physics of the observer and observation is still not well understood. Regardless of how observers are defined and whether classical or quantum principles are involved, physicists generally believe that classical information in some form is extracted from systems under observation (SUOs) in actual physics experiments. In all branches of science, their language reflects this belief: experimentalists talk of measuring an electron's spin or the mass of a new particle, and so on. The conceptual issues in quantum mechanics such as wave–particle duality, quantum interference, and nonlocality gave the first indication that all might not be well with this perspective. We need only to look at the photon concept to appreciate some of the problems with the idea that photons are particles (Paul, 2004). There are experiments where a photon (that is, a signal) is detected from a crystal, but the atom “from whence it came” cannot be identified, suggesting that a cooperative process is involved, rather like the phonon concept in the physics of crystals. The problem we have with the photon-as-particle concept is the gap in logic. If the particle interpretation is taken literally, then obvious questions about the physical structure or its equivalent of such particles spring up. Does such a particle have a “surface”? If it has a surface, what is that surface made of? These and other simple (minded) questions quickly lead to the conclusion that the particle concept is a convenient and economical objectification of context. In other words, a useful illusion.
Introduction In this chapter we show how the quantized detector network (QDN) formalism describes the double-slit (DS) experiment. This is arguably the simplest experiment that demonstrates quantum affects such as wave–particle duality and quantum interference. It continues to be the focus of much debate and experiment (Mardari, 2005), because theoretical modeling of what is going on reflects current understanding of quantum physics and hence physical reality.We will apply QDN to two variants: the original DS experiment and the monitored DS experiment, where an attempt is made to determine the imagined path of the particle. The DS experiment is widely acknowledged by physicists to be of importance to the understanding of quantum mechanics (QM). So much so that in 2002, the single electron version, first performed by Merli, Missiroli, and Pozzi (Merli et al., 1976), was voted by readers of Physics World to be “the most beautiful experiment in physics” (Rosa, 2012). The DS experiment can be discussed in terms of three stages, shown in Figure 10.1. By the end of the preparation stage, Σ 0 , a monochromatic beam of light or particles has been prepared by a source P , such as a laser. The beam emerges from point O and then passes through an information void V 1 to the first stage, Σ 1 , which consists of a wall or barrier W . This wall has two openings denoted A and B that allow parts of the beam to pass through into another information void V 2 and onto the second and final stage Σ 2 , which consists of a detecting screen S . The screen S is in general some material that can absorb and record particle impacts. In reality, any screen will consist of a finite number of signal detectors, such as photosensitive molecules, but the typical QM modeling is done as if there were a continuum of sites on the screen, such as C , that could register particles.
“I refute it thus!” Samuel Johnson famously dismissed Bishop George Berkeley's argument for the unreality of matter by kicking a large stone (Boswell, 1823). In the light of modern physics, however, Johnson's simple reasoning evaporates. Apparently solid matter is revealed, on closer inspection, to be almost all empty space, and the particles of which matter is composed are themselves ghostly patterns of quantum energy, mere excitations of invisible quantum fields, or possibly vibrating loops of string living in a ten-dimensional space–time (Greene, 1999). The history of physics is one of successive abstractions from daily experience and common sense, into a counterintuitive realm of mathematical forms and relationships, with a link to the stark sense data of human observation that is long and often tortuous. Yet at the end of the day, science is empirical, and our finest theories must be grounded, somehow, “in reality.” But where is reality? Is it in acts of observation of the world made by human and possibly non-human observers? In records stored in computer or laboratory notebooks? In some objective world “out there”? Or in a more abstract location? The ground of reality When a physicist performs an experiment, he or she interrogates nature and receives a response that, ultimately, is in the form of discrete bits of information (think of “yes” or “no” binary answers to specific questions), the discreteness implied by the underlying quantum nature of the universe (Zeilinger, 2004). Does reality then lie in the string of bits that come back from the set of all observations and experiments – a dry sequence of ones and zeros? Do these observations merely transfer really-existing bits of information from an external world reality to the minds of observers, or are the bits of information created by the very act of observation/experiment? And – the question to which this entire discussion is directed – are bits of “classical” information the only sort of information that count in the reality game, or does an altogether different form of information underpin reality? In short, where is the ontological ground on which our impression of a really-existing universe rests?
Introduction Throughout this book we have commented on the need to have a wider vision of physics as more than merely developing and solving equations of motion for states of systems under observation (SUOs). It is our premise that any attempt to discuss time needs to address issues such as the status of observers, apparatus, and suchlike, relative to those states of SUOs. This echoes the following quote from Wheeler: Stronger than the anthropic principle is what I might call the participatory principle. According to it we could not even imagine a universe that did not somewhere and for some stretch of time contain observers because the very building materials of the universe are these acts of observer participancy. You wouldn't have the stuff out of which to build the universe otherwise. This participatory principle takes for its foundation the absolutely central point of the quantum: No elementary phenomenon is a phenomenon until it is an observed (or registered) phenomenon. (Wheeler, 1979) We agree with Wheeler to this extent: there seems little, if any, point in speculating about truly unobservable parts of the Universe. If, however, there is a possibility that physical signals or effects from currently unobserved parts of the Universe might one day reach us, then that would in essence make those parts observable, albeit indirectly, and therefore suitable for theoretical analysis and speculation.
Modules ModulesIn this chapter, we discuss important modules such as Wollaston prisms, Newtonian prisms, beam splitters, phase shifters, mirrors, and null modules.Modules are pieces of apparatus placed at various strategic positions in the information void and are designed to influence labstate amplitudes at signal detectors.Modules are therefore a critical component in the quantized detector network (QDN) approach to quantum mechanics (QM).Modules are not classified as either real or virtual detectors, because no information is extracted from them.Their function is solely to influence quantum amplitude propagation between stages in specific ways.Even empty space (the vacuum) can be regarded as a module, for the propagation of signals through nominally "empty" space is a fundamental subject in its own right.A particularly important example illustrating how nontrivial that can be is the Hubble-Doppler red shift of light from distant galaxies.In the QDN description of the double-slit (DS) experiment, shown in Figure 10.2, the stage Σ 1 detectors labeled 1 1 and 2 1 may be considered as on the V 2 side of the wall W , where V 2 is the information void between stages Σ 1 and Σ 2 .Viewed in this way, the wall may be interpreted as a part of the apparatus that is positioned in the information void region V 1 so as to influence the signals obtained at detectors 1 1 and 2 1 .Virtually all experiments have similar components of apparatus in the information void.We shall call any such piece of apparatus a module.Modules are necessary to the architecture of the experiment, are situated in the information void, and therefore are not detectors.Examples of modules are Stern-Gerlach (SG) inhomogeneous field magnets, Wollaston prisms, mirrors, phase changers, and so on.Even empty space, otherwise known as the vacuum, should be regarded as a module.Each module has its own physical properties.These include the number of detectors feeding amplitudes into that module and the number of detectors that