Art Hobson | University of Arkansas (original) (raw)

Papers by Art Hobson

arXiv: Quantum Physics, 2017

There is evidence that superpositions of states of non-composite quantum systems A exist and can ... more There is evidence that superpositions of states of non-composite quantum systems A exist and can be interpreted as the simultaneous existence of two or more physically distinct quantum states of A. This paper shows, however, that entangled superposition states have a quite different character from simple superposition states. Whereas a simple superposition superposes two coherent states of a non-composite object A, entangled states superpose correlations between states of two incoherent subsystems A and B of a composite system AB. Thus an entangled state is best conceptualized as a coherent or phase-dependent superposition of correlations between incoherent or phase-independent subsystem states.

The Physics Teacher ◆ Vol. 50, May 2012 DOI: 10.1119/1.3703540 are really two parts of a single b... more The Physics Teacher ◆ Vol. 50, May 2012 DOI: 10.1119/1.3703540 are really two parts of a single black-and-green packet. Even if widely separated in space, they form a single unified field quantum. This is similar to a one-particle wave packet that is separated into two parts (e.g., a photon that has interacted with a half-reflecting mirror and is now a superposition of a wave packet that passed through the mirror and a packet that reflected from the mirror), but now there is a real excitation in each of the two parts. In classes for scientists or engineers, you could follow this qualitative description with an algebraic description.5 One popular entanglement method, used in the experiment described below, is called “spontaneous parametric down-conversion.” When photons pass through a certain kind of nonlinear crystal, a tiny fraction of them split into two photons of equal energy. It’s not understood why this occurs, but Leonard Mandel of the University of Rochester discovered that ...

arXiv (Cornell University), Dec 9, 2019

The entangled state that results when a detector measures a superposed quantum system has spawned... more The entangled state that results when a detector measures a superposed quantum system has spawned decades of concern about the problem of definite outcomes or "Schrodinger's cat." This state seems to describe a detector in an indefinite or "smeared" situation of indicating two macroscopic configurations simultaneously. This would be paradoxical. Since all entangled states are known to have nonlocal properties, and since measurements have obvious nonlocal characteristics, it's natural to turn to nonlocality experiments for insight into this question. Unlike the measurement situation where the phase is fixed at zero for perfect correlations, nonlocality experiments cover the full range of superposition phases and can thus show precisely what entangled states superpose. For two-state systems, these experiments reveal that the measurement state is not a superposition of two macroscopically different detector states but instead a superposition of two coherent correlations between distinct detector states and corresponding system states. In the measurement situation (i.e. at zero phase), and assuming the Schrodinger's cat scenario, the entangled state can be read as follows: An undecayed nucleus is perfectly correlated with an alive cat, AND a decayed nucleus is perfectly correlated with a dead cat, where "AND" indicates the superposition. This is not paradoxical.

Mario Bunge: A Centenary Festschrift, 2019

This paper presents a philosophically realistic analysis of quantization, field-particle duality,... more This paper presents a philosophically realistic analysis of quantization, field-particle duality, superposition, entanglement, nonlocality, and measurement. These are logically related: Realistically understanding measurement depends on realistically understanding superposition, entanglement, and nonlocality; understanding these three depends on understanding field-particle duality and quantization. This paper resolves all six, based on a realistic view of standard quantum physics. It concludes that, for these issues, standard quantum physics is consistent with scientific practice since Copernicus: Nature exists on its own and science's goal is to understand its operating principles, which are independent of humans. Quantum theory need not be regarded as merely the study of what humans can know about the microscopic world, but can instead view it as the study of real quanta such as electrons, photons, and atoms. This position has long been argued by Mario Bunge.

arXiv: Quantum Physics, 2019

A misunderstanding of entangled states has spawned decades of concern about quantum measurements ... more A misunderstanding of entangled states has spawned decades of concern about quantum measurements and a plethora of quantum interpretations. The "measurement state" or "Schrodinger's cat state" of a superposed quantum system and its detector is nonlocally entangled, suggesting that we turn to nonlocality experiments for insight into measurements. By studying the full range of superposition phases, these experiments show precisely what the measurement state does and does not superpose. These experiments reveal that the measurement state is not, as had been supposed, a paradoxical superposition of detector states. It is instead a nonparadoxical superposition of two correlations between detector states and system states. In this way, the experimental results resolve the problem of definite outcomes ("Schrodinger's cat"), leading to a resolution of the measurement problem. However, this argument does not yet resolve the measurement problem because it...

arXiv: Quantum Physics, 2018

Despite the unparalleled accuracy of quantum-theoretical predictions across an enormous range of ... more Despite the unparalleled accuracy of quantum-theoretical predictions across an enormous range of phenomena, the theory's foundations are still in doubt. The theory deviates radically from classical physics, predicts counterintuitive phenomena, and seems inconsistent. The biggest stumbling block is measurement, where the Schrodinger equation's unitary evolution seems inconsistent with collapse. These doubts have inspired a variety of proposed interpretations and alterations of the theory. Most interpretations posit the theory represents only observed appearances rather than reality. The realistic interpretations, on the other hand, posit entities such as other universes, hidden variables, artificial collapse mechanisms, or human minds, that are not found in the standard mathematical formulation. Surprisingly, little attention has been paid to the possibility that the standard theory is both realistic and correct as it stands. This paper examines several controversial issues, ...

The Physics Teacher, 2004

Quantum Engineering, 2022

The entangled “measurement state” (MS), predicted by von Neumann to arise during quantum measurem... more The entangled “measurement state” (MS), predicted by von Neumann to arise during quantum measurement, seems to display paradoxical properties such as multiple macroscopic outcomes. But analysis of interferometry experiments using entangled photon pairs shows that entangled states differ surprisingly from simple superposition states. Based on standard quantum theory, this paper shows that the MS (i) does not represent multiple detector readings but instead represents nonparadoxical multiple statistical correlations between system states and detector readings, (ii) implies that exactly one outcome actually occurs, and (iii) implies that when one outcome occurs, the other possible outcomes simultaneously collapse nonlocally. Point (iii) resolves an issue first raised in 1927 by Einstein who demonstrated that quantum theory requires instantaneous state collapse. This conundrum’s resolution requires nonlocal correlations, which from today’s perspective suggests the MS should be an entang...

arXiv: Quantum Physics, 2017

Theory and experiment both demonstrate that an entangled quantum state of two subsystems is neith... more Theory and experiment both demonstrate that an entangled quantum state of two subsystems is neither a superposition of states of its subsystems nor a superposition of composite states but rather a coherent superposition of nonlocal correlations between incoherently mixed local states of the two subsystems. Thus, even if one subsystem happens to be macroscopic as in the entangled "Schrodinger's cat" state resulting from an ideal measurement, this state is not the paradoxical macroscopic superposition it is generally presumed to be. It is, instead, a "macroscopic correlation," a coherent quantum correlation in which one of the two correlated sub-systems happens to be macroscopic. This clarifies the physical meaning of entanglement: When a superposed quantum system A is unitarily entangled with a second quantum system B, the coherence of the original superposition of different states of A is transferred to different correlations between states of A and B, so the...

The quantum measurement problem still finds no consensus. Nonlocal interferometry provides an unp... more The quantum measurement problem still finds no consensus. Nonlocal interferometry provides an unprecedented experimental probe by entangling two photons in the "measurement state" (MS). The experiments show that each photon "measures" the other; the resulting entanglement decoheres both photons; decoherence collapses both photons to unpredictable but definite outcomes; and the two-photon MS continues evolving coherently. Thus, contrary to common opinion, when a two-part system is in the MS, the outcomes actually observed at both subsystems are definite. Although standard quantum physics postulates definite outcomes, two-photon interferometry verifies them to be not only consistent with, but actually a prediction of, the other principles. Nonlocality is the key to understanding this. As a consequence of nonlocality, the states we actually observe are the local states. These actually-observed local states collapse, while the global MS, which can be "observed&q...

arXiv: Quantum Physics, 2013

The quantum measurement problem still finds no consensus. Nonlocal interferometry provides an unp... more The quantum measurement problem still finds no consensus. Nonlocal interferometry provides an unprecedented experimental probe by entangling two photons in the "measurement state" (MS). The experiments show that each photon "measures" the other; the resulting entanglement decoheres both photons; decoherence collapses both photons to unpredictable but definite outcomes; and the two-photon MS continues evolving coherently. Thus, contrary to common opinion, when a two-part system is in the MS, the outcomes actually observed at both subsystems are definite. Although standard quantum physics postulates definite outcomes, two-photon interferometry verifies them to be not only consistent with, but actually a prediction of, the other principles. Nonlocality is the key to understanding this. As a consequence of nonlocality, the states we actually observe are the local states. These actually-observed local states collapse, while the global MS, which can be "observed&q...

Science & Global Security, 1991

Contemporary Physics

This paper reviews and suggests a resolution of the problem of definite outcomes of measurement. ... more 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.

Physics Teacher, May 1, 2011

Journal of College Science Teaching, 2000

arXiv: Quantum Physics, 2017

There is evidence that superpositions of states of non-composite quantum systems A exist and can ... more There is evidence that superpositions of states of non-composite quantum systems A exist and can be interpreted as the simultaneous existence of two or more physically distinct quantum states of A. This paper shows, however, that entangled superposition states have a quite different character from simple superposition states. Whereas a simple superposition superposes two coherent states of a non-composite object A, entangled states superpose correlations between states of two incoherent subsystems A and B of a composite system AB. Thus an entangled state is best conceptualized as a coherent or phase-dependent superposition of correlations between incoherent or phase-independent subsystem states.

The Physics Teacher ◆ Vol. 50, May 2012 DOI: 10.1119/1.3703540 are really two parts of a single b... more The Physics Teacher ◆ Vol. 50, May 2012 DOI: 10.1119/1.3703540 are really two parts of a single black-and-green packet. Even if widely separated in space, they form a single unified field quantum. This is similar to a one-particle wave packet that is separated into two parts (e.g., a photon that has interacted with a half-reflecting mirror and is now a superposition of a wave packet that passed through the mirror and a packet that reflected from the mirror), but now there is a real excitation in each of the two parts. In classes for scientists or engineers, you could follow this qualitative description with an algebraic description.5 One popular entanglement method, used in the experiment described below, is called “spontaneous parametric down-conversion.” When photons pass through a certain kind of nonlinear crystal, a tiny fraction of them split into two photons of equal energy. It’s not understood why this occurs, but Leonard Mandel of the University of Rochester discovered that ...

arXiv (Cornell University), Dec 9, 2019

The entangled state that results when a detector measures a superposed quantum system has spawned... more The entangled state that results when a detector measures a superposed quantum system has spawned decades of concern about the problem of definite outcomes or "Schrodinger's cat." This state seems to describe a detector in an indefinite or "smeared" situation of indicating two macroscopic configurations simultaneously. This would be paradoxical. Since all entangled states are known to have nonlocal properties, and since measurements have obvious nonlocal characteristics, it's natural to turn to nonlocality experiments for insight into this question. Unlike the measurement situation where the phase is fixed at zero for perfect correlations, nonlocality experiments cover the full range of superposition phases and can thus show precisely what entangled states superpose. For two-state systems, these experiments reveal that the measurement state is not a superposition of two macroscopically different detector states but instead a superposition of two coherent correlations between distinct detector states and corresponding system states. In the measurement situation (i.e. at zero phase), and assuming the Schrodinger's cat scenario, the entangled state can be read as follows: An undecayed nucleus is perfectly correlated with an alive cat, AND a decayed nucleus is perfectly correlated with a dead cat, where "AND" indicates the superposition. This is not paradoxical.

Mario Bunge: A Centenary Festschrift, 2019

This paper presents a philosophically realistic analysis of quantization, field-particle duality,... more This paper presents a philosophically realistic analysis of quantization, field-particle duality, superposition, entanglement, nonlocality, and measurement. These are logically related: Realistically understanding measurement depends on realistically understanding superposition, entanglement, and nonlocality; understanding these three depends on understanding field-particle duality and quantization. This paper resolves all six, based on a realistic view of standard quantum physics. It concludes that, for these issues, standard quantum physics is consistent with scientific practice since Copernicus: Nature exists on its own and science's goal is to understand its operating principles, which are independent of humans. Quantum theory need not be regarded as merely the study of what humans can know about the microscopic world, but can instead view it as the study of real quanta such as electrons, photons, and atoms. This position has long been argued by Mario Bunge.

arXiv: Quantum Physics, 2019

A misunderstanding of entangled states has spawned decades of concern about quantum measurements ... more A misunderstanding of entangled states has spawned decades of concern about quantum measurements and a plethora of quantum interpretations. The "measurement state" or "Schrodinger's cat state" of a superposed quantum system and its detector is nonlocally entangled, suggesting that we turn to nonlocality experiments for insight into measurements. By studying the full range of superposition phases, these experiments show precisely what the measurement state does and does not superpose. These experiments reveal that the measurement state is not, as had been supposed, a paradoxical superposition of detector states. It is instead a nonparadoxical superposition of two correlations between detector states and system states. In this way, the experimental results resolve the problem of definite outcomes ("Schrodinger's cat"), leading to a resolution of the measurement problem. However, this argument does not yet resolve the measurement problem because it...

arXiv: Quantum Physics, 2018

Despite the unparalleled accuracy of quantum-theoretical predictions across an enormous range of ... more Despite the unparalleled accuracy of quantum-theoretical predictions across an enormous range of phenomena, the theory's foundations are still in doubt. The theory deviates radically from classical physics, predicts counterintuitive phenomena, and seems inconsistent. The biggest stumbling block is measurement, where the Schrodinger equation's unitary evolution seems inconsistent with collapse. These doubts have inspired a variety of proposed interpretations and alterations of the theory. Most interpretations posit the theory represents only observed appearances rather than reality. The realistic interpretations, on the other hand, posit entities such as other universes, hidden variables, artificial collapse mechanisms, or human minds, that are not found in the standard mathematical formulation. Surprisingly, little attention has been paid to the possibility that the standard theory is both realistic and correct as it stands. This paper examines several controversial issues, ...

The Physics Teacher, 2004

Quantum Engineering, 2022

The entangled “measurement state” (MS), predicted by von Neumann to arise during quantum measurem... more The entangled “measurement state” (MS), predicted by von Neumann to arise during quantum measurement, seems to display paradoxical properties such as multiple macroscopic outcomes. But analysis of interferometry experiments using entangled photon pairs shows that entangled states differ surprisingly from simple superposition states. Based on standard quantum theory, this paper shows that the MS (i) does not represent multiple detector readings but instead represents nonparadoxical multiple statistical correlations between system states and detector readings, (ii) implies that exactly one outcome actually occurs, and (iii) implies that when one outcome occurs, the other possible outcomes simultaneously collapse nonlocally. Point (iii) resolves an issue first raised in 1927 by Einstein who demonstrated that quantum theory requires instantaneous state collapse. This conundrum’s resolution requires nonlocal correlations, which from today’s perspective suggests the MS should be an entang...

arXiv: Quantum Physics, 2017

Theory and experiment both demonstrate that an entangled quantum state of two subsystems is neith... more Theory and experiment both demonstrate that an entangled quantum state of two subsystems is neither a superposition of states of its subsystems nor a superposition of composite states but rather a coherent superposition of nonlocal correlations between incoherently mixed local states of the two subsystems. Thus, even if one subsystem happens to be macroscopic as in the entangled "Schrodinger's cat" state resulting from an ideal measurement, this state is not the paradoxical macroscopic superposition it is generally presumed to be. It is, instead, a "macroscopic correlation," a coherent quantum correlation in which one of the two correlated sub-systems happens to be macroscopic. This clarifies the physical meaning of entanglement: When a superposed quantum system A is unitarily entangled with a second quantum system B, the coherence of the original superposition of different states of A is transferred to different correlations between states of A and B, so the...

The quantum measurement problem still finds no consensus. Nonlocal interferometry provides an unp... more The quantum measurement problem still finds no consensus. Nonlocal interferometry provides an unprecedented experimental probe by entangling two photons in the "measurement state" (MS). The experiments show that each photon "measures" the other; the resulting entanglement decoheres both photons; decoherence collapses both photons to unpredictable but definite outcomes; and the two-photon MS continues evolving coherently. Thus, contrary to common opinion, when a two-part system is in the MS, the outcomes actually observed at both subsystems are definite. Although standard quantum physics postulates definite outcomes, two-photon interferometry verifies them to be not only consistent with, but actually a prediction of, the other principles. Nonlocality is the key to understanding this. As a consequence of nonlocality, the states we actually observe are the local states. These actually-observed local states collapse, while the global MS, which can be "observed&q...

arXiv: Quantum Physics, 2013

The quantum measurement problem still finds no consensus. Nonlocal interferometry provides an unp... more The quantum measurement problem still finds no consensus. Nonlocal interferometry provides an unprecedented experimental probe by entangling two photons in the "measurement state" (MS). The experiments show that each photon "measures" the other; the resulting entanglement decoheres both photons; decoherence collapses both photons to unpredictable but definite outcomes; and the two-photon MS continues evolving coherently. Thus, contrary to common opinion, when a two-part system is in the MS, the outcomes actually observed at both subsystems are definite. Although standard quantum physics postulates definite outcomes, two-photon interferometry verifies them to be not only consistent with, but actually a prediction of, the other principles. Nonlocality is the key to understanding this. As a consequence of nonlocality, the states we actually observe are the local states. These actually-observed local states collapse, while the global MS, which can be "observed&q...

Science & Global Security, 1991

Contemporary Physics

This paper reviews and suggests a resolution of the problem of definite outcomes of measurement. ... more 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.

Physics Teacher, May 1, 2011

Journal of College Science Teaching, 2000