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arXiv:quant-ph/9712050

The zeropoint field - no longer a ghost

Trevor W. Marshall

Published Dec 21, 1997• 0 citations
arXivHTMLPDF

Abstract

We develop a local realist analysis of parametric down conversion, based on the recognition that the pump field, instead of down converting spontaneously, does so through its nonlinear coupling with a real zeropoint, or "vacuum" electromagnetic field. The theory leads tothe prediction of a new phenomenon - that, in addition to the main down-conversion rainbow, there is a satellite rainbow, whose intensity is about 3 per cent of the main one. Confirmation of this prediction will call seriously into question the current description of the light field in terms of photons. The present article extends the analysis of its predecessors (this archive, numbers 9711029 and 9712001) to take account of the pump's polarization>

DOI
10.48550/arxiv.quant-ph/9712050

Related papers

The myth of the down converted photon

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Parametric down conversion (PDC) is widely interpreted in terms of photons, but, even among supporters of this interpretation, many properties of the photon pairs have been described as "mind-boggling" and even "absurd". In this article we argue that a classical description of the light field, taking account of its vacuum fluctuations, leads us to a consistent and rational account of all PDC phenomena. "Nonlocality" in quantum optics is simply an artifact of the Photon Concept. We also predict a new phenomenon, namely the appearance of a second, or satellite PDC rainbow.

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Introduction

P. D. Drummond, Mark S. Hillery

Nonlinear optics is the study of the response of dielectric media to strong optical fields. The fields are sufficiently strong that the response of the medium is, as its name implies, nonlinear. That is, the polarization, which is the dipole moment per unit volume in the medium, is not a linear function of the applied electric field. In the equation for the polarization, there is a linear term, but, in addition, there are terms containing higher powers of the electric field. This leads to significant new types of behavior, one of the most notable being that frequencies different from that of the incident electromagnetic wave, such as harmonics or subharmonics, can be generated. Linear media do not change the frequency of light incident upon them. The first observation of a nonlinear optical effect was, in fact, second-harmonic generation – a laser beam entering a nonlinear medium produced a second beam at twice the frequency of the original. Another type of behavior that becomes possible in nonlinear media is that the index of refraction, rather than being a constant, is a function of the intensity of the light. For a light beam with a nonuniform intensity profile, this can lead to self-focusing of the beam. Most nonlinear optical effects can be described using classical electromagnetic fields, and, in fact, the initial theory of nonlinear optics was formulated assuming the fields were classical. When the fields are quantized, however, a number of new effects emerge. Quantized fields are necessary if we want to describe fields that originate from spontaneous emission. For example, in a process known as spontaneous parametric down-conversion, a beam of light at one frequency, the pump, produces a beam at half the original frequency, the signal. This second beam is a result of spontaneous emission.

Cambridge University Press eBooks•Mar 27, 2014•0 citations
We develop a local realist analysis of parametric down conversion, based on the recognition that the pump field, instead of down converting spontaneously, does so through its nonlinear coupling with a real zeropoint, or "vacuum" electromagnetic field. The theory leads tothe prediction of a new phenomenon - that, in addition to the main down-conversion rainbow, there is a satellite rainbow, whose intensity is about 3 per cent of the main one. Confirmation of this prediction will call seriously into question the current description of the light field in terms of photons. The present article extends the analysis of its predecessors (this archive, numbers 9711029 and 9712001) to take account of the pump's polarization>
Parametric down conversion (PDC) is widely interpreted in terms of photons, but, even among supporters of this interpretation, many properties of the photon pairs have been described as "mind-boggling" and even "absurd". In this article we argue that a classical description of the light field, taking account of its vacuum fluctuations, leads us to a consistent and rational account of all PDC phenomena. "Nonlocality" in quantum optics is simply an artifact of the Photon Concept. We also predict a new phenomenon, namely the appearance of a second, or satellite PDC rainbow.
In a series of articles we have shown that all parametric-down- conversion processes, both of type-I and type-II, may be described by a positive Wigner density. These results, together with our description of how light detectors subtract the zeropoint radiation, indicated the possibility of a completely local realist theory of all these processes. In the present article we show how the down-converted fields may be described as retarded fields, generated by currents inside the nonlinear crystal, thereby achieving such a theory. Most of its predictions coincide with the standard nonlocal theory. However, the intensities of the down converted signals do not correspond exactly with the photon pairs of the nonlocal theory. For example, in a blue- red down conversion we would find 1.03 red "photons" for every blue one. The theory also predicts a new phenomenon, namely parametric up conversion from the vacuum.
We demonstrate that the phenomenon known as Spontaneous Parametric Down Conversion is really an amplification, in a nonlinear crystal pumped by a laser, of certain pairs of modes of the electromagnetic zeropoint field. The demonstration is achieved by showing the existence of a related phenomenon, Spontaneous Parametric Up Conversion. This phenomenon, once observed, will cast doubt on the quantum-optical theory, which treats photons as the elementary objects of the light field. It will also lend greater credibility to the zeropoint-field description of optical entanglement phenomena. That description is based on the unquantized light field and is consistently local, in contrast with the nonlocal description of Quantum Optics.
The Wigner formalism in the Heisenberg picture constitutes a bridge that connects Quantum Optics to Stochastic Optics. The vacuum field appears explicitly in the formalism, and the wavelike aspects of light are emphasised. In addition, the zeropoint intensity as a threshold for detection is a common denominator in both theories. In this paper, after summarising the basic rules of the Wigner approach and its application to parametric down-conversion, some new results are presented that delve into the physical meaning of the zeropoint field in optical quantum communication. Specifically, the relationship between Bell-state distinguishability and the number of sets of zeropoint modes that take part in the experiment is analysed in terms of the coupling between the phases of the different fields involved and the subtraction of the zeropoint intensity at the detectors. Additionally, the connection between the compatibility theorem in quantum cryptography and zeropoint field is stressed.
Nonlinear optics is the study of the response of dielectric media to strong optical fields. The fields are sufficiently strong that the response of the medium is, as its name implies, nonlinear. That is, the polarization, which is the dipole moment per unit volume in the medium, is not a linear function of the applied electric field. In the equation for the polarization, there is a linear term, but, in addition, there are terms containing higher powers of the electric field. This leads to significant new types of behavior, one of the most notable being that frequencies different from that of the incident electromagnetic wave, such as harmonics or subharmonics, can be generated. Linear media do not change the frequency of light incident upon them. The first observation of a nonlinear optical effect was, in fact, second-harmonic generation – a laser beam entering a nonlinear medium produced a second beam at twice the frequency of the original. Another type of behavior that becomes possible in nonlinear media is that the index of refraction, rather than being a constant, is a function of the intensity of the light. For a light beam with a nonuniform intensity profile, this can lead to self-focusing of the beam. Most nonlinear optical effects can be described using classical electromagnetic fields, and, in fact, the initial theory of nonlinear optics was formulated assuming the fields were classical. When the fields are quantized, however, a number of new effects emerge. Quantized fields are necessary if we want to describe fields that originate from spontaneous emission. For example, in a process known as spontaneous parametric down-conversion, a beam of light at one frequency, the pump, produces a beam at half the original frequency, the signal. This second beam is a result of spontaneous emission.