The Theory of Calibration - Isology
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Transcript of The Theory of Calibration - Isology
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The Theory of Calibration and measurement discontinuity
Ken Krechmer 15 April 2015
Abstract: An experimental measurement system consists of a variable, a measuring instrument and a reference. In linear algebra a reference may be formally described as a basis. Calibration correlates this basis of the reference with the basis of the measuring instrument. Prior to calibration, the measuring instrument's results cannot be correlated to other measuring instruments. A formal theory of calibration is developed. Calibration is proven to make a small change in the entropy of a distribution of experimental measurement results of a continuous variable. This small entropy change (calibration entropy) is unintentionally ignored in quantum measurement theories. In experimental measurement results the effect of calibration entropy is intentionally ignored when it is less than the measurement precision. Calibration entropy is proven to be the cause of the measurement discontinuity that appears both in quantum measurement theory and between the theory and experimental measurement results.
I INTRODUCTION TO CALIBRATION
Neither classical nor quantum mechanics provide a theory of calibration. Representational measurement,1 the currently applied theory of measurement, is based upon the representation of a variable by a measuring instrument and does not consider a reference.2 Metrology, the science of experimental measurement, is where the practice of calibration to a reference is defined. Based upon the practical definitions used in metrology,3 this paper develops a formal theory of calibration and applies it to quantum measurement theory (as described in Section V) to verify the theory of calibration.
Calibration is the process of adjusting an experimental measuring instrument to correlate its results with defined measurement units.4 Without calibration it is not possible to validate experimental results or compare measurement results between two measuring instruments, which is the purpose of a measurement. Experimental measurements of continuous variables require calibration adjustments.
Consider a voltmeter (measuring instrument) before a voltage (continuous variable) measurement is made. The metrology practice is to calibrate the voltmeter to a voltage source (reference, e.g., 3.00V) which is correlated (applying metrology) to a voltage standard [5.4]. The calibration process consists of: the 0.00 voltage of the voltmeter is set, the 3.00 volt source is applied and then the voltmeter is adjusted until 300 0.01 volt increments are indicated, where 0.01 is the smallest magnitude measurement increment of this voltmeter. When the calibration adjustment is fixed, multiple voltmeter measurement results of the same source are expected to be within +/- 1%, which is the measurement precision [2.15] of the voltmeter. The calibration adjustment of the voltmeter must have a finer resolution [4.14] than the measurement precision.
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This example makes clear that any calibration adjustment must cause a change in the entropy of a distribution of measurement results of the same variable. When this change is not recognized in theoretical measurement calculations, entropy is not conserved and a measurement discontinuity appears. This discontinuity appears in von Neumann's process 15 calculations, and Heisenberg uncertainty relations (equation 17) when compared with experimental measurement results.
II THE PRACTICE OF CALIBRATION Another example of calibration, based upon a metre measuring stick, introduces the
necessary metrology terms. The metre stick, an experimental measuring instrument [3.1], is divided into a set of n = 1000 measurement increments (not defined in VIM). By metrology processes, these measurement increments may be calibrated [2.39] to be between: 0.990 -‐ 1.010 of 1/1000 of a standard metre. In this example, there are 20 resolution increments (r) in the ±1% precision range. Here the standard metre is the measurement standard [5.1], and 1/1000 of the standard metre is the minimum measurement unit [1.9] applied as a reference. When each measurement increment is compared to the reference, calibration corrections [2.53] are generated and each measurement increment of the measurement instrument becomes a calibrated measurement increment. Then, the magnitude of a variable [2.3, measurand in VIM] expressed in calibrated measurement increments represents a measurement result [2.9] correlated to a measurement standard.
One measurement result using the metre measuring stick defined above is 500 millimetres. Where, 500 is the magnitude, millimetre is the referenced measurement unit, the range of precision of a measurement is +/-1%, therefore the resolution of each calibrated measurement increment is +/- 1 % and the minimum calibration adjustment (r) is 0.1% of an increment. Graphing the 500 x 20 = 10000 possible variations of measurement results (many of equal magnitude) forms a Gaussian distribution.
Consider the initial calibration (by the instrument maker) of the voltmeter's smallest increments of 0.01 volt measurement units or multiples thereof. Prior to this calibration the measurement increments are uncorrelated and a measurement indication [4.1] (a magnitude of measurement increments) cannot be compared to a measurement result from other calibrated measuring instruments. The measurement unit, while arbitrary, establishes a measurement result that is correlated externally. It is well known that calibration often is responsible for a small change in an experimental measurement result. Both to take into account such small changes and for experimental verification, calibrated measurement increments must be included in any measurement theory. This requires a relational measurement theory.6
Relational measurement theory allows measurement results that are comparable, as it includes a reference (which has a defined statistical correlation to a measurement standard), a measuring instrument and a variable. The reference and the measuring instrument interact and the measuring instrument and the variable interact. Both independent interactions are necessary to correlate the variable to the reference and are part of the metrology definition of a measurement [2.1].
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In relational measurement theory, a variable lacks both magnitude and basis until correlated to a reference. When a calibrated measuring instrument is applied to a variable, the resulting magnitude of calibrated measurement increments correlates the measurement of the variable to a reference (basis). In relational measurements, position is measured over a reference distance (e.g., metre) and momentum is measured over a reference time (e.g., second).
One quantum measurement example of momentum measurements over time is the single slit or hole experiments.7 In these experiments a measuring instrument (with source, mask and plate) is used. The source provides the variables, the mask presents the diameter of a hole or width of the slit to establish the measurement increment (wavelength) and the plate collects the projection over time (an Airy pattern8) which is the momentum measurement results. A formal demonstration of the relation between position and momentum precision is: the Fourier transform of a distribution of measurements of one position (a Gaussian distribution) is an Airy pattern of momentum measurements.
III THE THEORY OF CALIBRATION The metre measuring stick is a physical example of a one dimension basis in linear algebra.
In a representational measurement a variable is correlated to the metre stick. This correlation is formalized as a linear transform (3) between the measuring instrument and the variable.9 In this paper, calibration, the statistical correlation between the measuring instrument and the reference, is also formalized as a transform (2). Together the two processes, calibration and representational measurement, formalize a relational measurement (4).
Consider the calibration matrix A consisting of two basis, the reference column Xi and the measuring instrument row Xj with n different increments xi (all xi are statistically correlated to a measurement standard) and xj (the smallest measuring instrument increment) respectively. In matrix A, the matrix operator (1) defines the calibration ratios aij :
where i, j = 1 to n (1)
Matrix A is a square n x n diagonal matrix, where the non-‐zero elements are on the main diagonal, a11 - ann. These calibration ratios, aij represent the ratio of xi to xj', where the prime (') indicates xj' includes calibration corrections. The magnitude of xj' is similar to xj but has greater resolution. Then calibration formally is the transformation in (2):
(2)
A representational measurement, in a one dimension formalism, is mxj (3), where m ( ) is the magnitude of the variable in xj uncorrelated units. As a representational measurement does not include calibration, mxj is a measurement indication that is uncorrelated externally.
(3)
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A relational measurement, shown in (4), includes the calibration transformation (2) to change a measurement indication (3) into a measurement result. After calibration, each xj' is within the defined precision relative to a measurement standard. The calibrated measurement increments (xj') are correlated to xi, wherever and whenever xi is applied. Equation (4) formalizes the metrology definition of an experimental measurement.
(4)
IV CALIBRATION ENTROPY
Based upon (1) above, each aij in (4) statistically varies from 0.990 to 1.010. This statistical variance identifies that (1) is not a linear operator as each aij is not a constant. Then Xi and Xj are linearly independent and A must be a nonsingular matrix. When a square matrix (m x m is a square matrix) is nonsingular, its determinate is not zero, which means any non-‐zero calibration (2), causes a positive entropy change. This calibration entropy is calculated using Shannon entropy as the m states are mutually exclusive.10
The measuring instrument's entropy change caused by a basis transformation due to calibration is calculated from the determinate of A (shown in (5) as |aij|). Since matrix A is diagonal, the determinate is calculated by:
(5)
Then the Jacobian, the reciprocal of the determinate in this case, is . This is used to
calculate the calibration entropy, H(aij), which is the natural log of this Jacobian: (6)
When calibration changes aij there is an entropy change. This entropy change may be so small as to be close to changes due to other sources of experimental measurement uncertainty [2.26]. But the calibration entropy is greater than zero, as the above proves. When calibration is expressed as entropy, the two calibration effects, adjustment and an external basis, appear as H(aij) and ln r -‐ H(aij) respectively.11 Where ln r is the maximum entropy caused by changes in the precision of the measurement increments when correlated to measurement standard units. ln r is usually significantly smaller than ln n, the maximum entropy of the measuring instrument.
V CALIBRATION IN QUANTUM MEASUREMENT THEORY Quantum measurement theory is formalized in a complex vector-‐space (Hilbert space).
Consistent with the application of relational measurement theory, relational quantum mechanics theory is also applied.12 Then, "the discontinuous, non-‐causal and instantaneously acting"13 change (unrelated to any interactions between the variable and the measuring instrument), which is described by von Neumann process 1, is calibration. Reviewing von Neumann's process 1 function in matrix form14 identifies it is identical to (2), calibration. This
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explains why the von Neumann process 1 is time independent and the von Neumann process 2 (the Schrödinger wave equation) is not.
In quantum measurement theory von Neumann's process 1 transforms a state vector (representing a variable) into an eigenvector, which is a magnitude of complex unit vectors relative to an eigenbasis set (measuring instrument). The square modulus of this eigenvector is the probability of a specific eigenvalue in unit vectors and the quantum measurement result.
von Neumann process 1 is the calibration process and the square modulus is the representational measurement process. A representational measurement is an inner product in vector space, the angle (θ) between the eigenvector representing the variable and the eigenbasis set representing the measuring instrument is zero and xi = xj = x, a complex unit increment without an external basis. Then the inner product of the eigenvector and eigenbasis set increments is x2 cos θ where θ = 0°, cos θ = 1 which identifies the complex square in Hilbert space (square modulus) is a representational measurement process. In this representational measurement the complex unit vectors (x) are exactly equal and not correlated to an external basis. Lacking an external basis the sum of n unit vectors (nx) can only be one. That is, x = 1/n or nx = 1, which defines a probability distribution, and x' (calibrated) does not exist because there is no correlation to an external basis.
It is beautiful to recognize that quantum measurement theory includes calibration before a measurement, but the effect of calibration in Hilbert space is uncorrelated to experimental results. This identifies why a specific measurement result in Hilbert space appears indeterminate, but is not random.
VI CALIBRATION ENTROPY IN A VECTOR SPACE. Since the eigenvalue probability magnitude in unit vectors and experimental results in
calibrated measurement increments are fundamentally different, the effect of calibration on quantum measurement theory is developed using entropy forms. In the position measurement matrix A, H(xj) is the entropy of a measuring instrument based upon the position measurement increments. The entropy after the basis change caused by calibration is H(x') where: 15
(7)
Consider a momentum measurement matrix B where H(pj) is the entropy of a measuring instrument based upon the momentum measurement increments. The entropy after a basis change caused by calibration is H(p') where:
(8)
The entropic Heisenberg Uncertainty Relation (HUR) between position and the related momentum is well known.16 Equations (10) and (9) present this relation before and after calibration. c is a constant positive magnitude.
(9)
(10)
In a Gaussian distribution of entropy case, (9) and (10) may be combined:
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(11)
Substituting (7) and (8) in the left hand side of (11) produces:
(12)
Combining terms in (12) produces:
(13)
Equation (13) proves that a change in the entropy of the position measurement increments distribution, due to calibration, becomes an equal and opposite change in the entropy of the momentum measurement increments distribution. Applying (6) in both position and momentum forms to (13), (14) proves (Gaussian entropy distribution only) that the distributions of aij and bij are the same (although aij and bij are order independent).
(14)
VII CALIBRATION ENTROPY IN UNCERTAINTY RELATIONS The calibration entropy appears as a difference from the expected experimental results via
the HUR (17). 17 HUR formalizes how a change in the distribution of one variable causes a change in the distribution of a second variable related by a Fourier transform. Such variables are termed complementary. The HUR operates at all scales and applies to distributions when the calibration ratios change. The aspect of HUR that has been unclear occurs when the calibration entropy is not included in quantum measurement theory and the effect of the calibration entropy of the first variable appears (without recognized cause) in experiments measuring the complementary variable.18 This aspect of HUR is formalized below:
Based upon (2), the standard deviation (σ) of the calibration ratios related to a measurement m is:
(15)
In (15) σa ≠ 1 except when all aij = 1. In (15), uniform distributions of calibration ratios do not cancel as in (4), the one dimension form.
(16)
The calibrated measurement increments (xj') change, via the HUR, the measurement increments of the complementary variable (pj). Equation (16) for both xi, a position measurement unit (with aij) and pi, a momentum measurement unit (with bij), is applied to (17) and results in (18). In (17) h is the Planck constant.
(17) 19
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(18)
The two standard deviation terms in (18) are based upon aij and bij which are order independent. Applying (14) to (18) proves that the calibration which causes xj' (16) is the origin of the momentum distribution change, σbpi. The HUR is not uncertain, but a change must be greater than one half the Planck constant (h), the minimum quantum measurement unit.
VIII WHY CALIBRATION IS NOT CONSIDERED 1. One assumption is that calibration only effects experimental measurements. That is,
calibration makes an experimental measurement indication (where the xj vary) more closely correlate with the theory (where the xj are fixed). Recognizing that entropy must be conserved, (6) makes this assumption problematic.
2. In one dimensional measurements ( ) these assumptions are often made: a) the distribution of calibration corrections (aj) is uniform about the mean (e.g.,
Gaussian).
b) m >> xj.
c) xj >> precision.
Applying a) and b), the mean of aj is very close to one. Applying c), the change due to calibration is less than the smallest measurement increment. These assumptions are not valid when measuring the magnitude of variables near to Planck's constant.
3. Considering calibration one dimensional supports the mean as the parameter of the calibration distribution. Calibration corrections are at least two dimensional (e.g., matrix A) which requires the standard deviation (15) as the parameter of the calibration distribution.
4. Hilbert space calculations cannot correlate with experimental results.
5. Currently, formal measurements (3) are based upon representational measurement theory, which does not apply calibration independently. Two representational measurements (one being calibration) can model a relational measurement system.
IX CORROBORATING EVIDENCE 1) The calibration entropy occurs when calibration adjustments are applied to a set of
experimental measurement indications. This entropy change does not occur again and additional measurement results of an unchanged variable are unchanged until the next calibration adjustment. This initializing property of the calibration entropy is identified in experiments, e.g., the Compton and Simons experiments (endnote 19).
2) Calibration establishes a distribution of non-‐linear measurement increments. This is in agreement with the theory presented by E. P. Wigner who proved that the cause of the discontinuity could not be described by the linear laws of quantum mechanics.20
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3) In quantum measurement theory, a discrete variable allows measurements without a discontinuity.21 In experimental measurements, the equivalent is a variable with discrete equal increments. As an example, counting the teeth of a gear to measure rotation. In these cases there is no calibration (all gear teeth are assumed to be equal) and therefore no calibration entropy.
4) Experimental quantum weak measurements (QWM) reduce H(aij) by addressing measurements with small n (e.g., spin, where n = 2).22 In equation (6) when |aij| > 1, H(aij) increases and when |aij|< 1, H(aij) decreases. Then distributions of spin elements almost zero H(aij), which makes QWM practical.
5) Section V identifies the Born Rule23 (square modulus) as the representational measurement part of a relational measurement.
6) The Schrödinger's cat thought experiment is an example of how representational measurements alone, uncorrelated to a reference (alive/dead), do not represent experimental results.24
7) Calibration is a basis transformation representing changes nearer the Planck constant. The Lorentz transform, in relativistic mechanics, is a basis transformation representing changes nearer the velocity of light.25
8) The unacknowledged calibration entropy is the reason that quantum measurement theories do not describe experimental results, which was proven in the Einstein, Podolsky and Rosen paper.26
X CONCLUSIONS Calculating calibration separately from a measurement assumes a one dimension
representational measurement system. This assumption is valid in many classical measurement calculations, but not in Hilbert space calculations. While metrology identifies that calibration is part of a measurement, relational measurement theory is necessary to include calibration. In relational measurement theory, external references are required to compare experimental results. Calibration correlates the measuring instrument to the external reference.
Without a correlated external reference, quantum measurement theory represents experimental measurement results probabilistically. Including the effect of calibration to references in quantum measurement theory removes the measurement discontinuity and unifies quantum and classical measurements.
1 D. H. Krantz, R. D. Luce, P. Suppes, A. Tversky, Foundations of Measurement, Academic Press, New York, 1971. This three volume work is the foundational text on representational measurement.
2 D. J. Hand, Measurement Theory and Practice, Oxford University Press, New York, NY, 2004. This book, as one example of many, does not formalize a calibration process or quantify a calibration result to a measurement.
3 When metrology terms are first used, they are referenced [x.x] to the practical definitions in the International Vocabulary of Metrology (VIM) 3rd edition, BIPM JCGM 200:2012, http://www.bipm.org/en/publications/guides/vim.html
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4 A.E. Fridman, The Quality of Measurements: A Metrological Reference, Springer Science+Business Media, page 132, (metrological definition of calibration), 2012
5 J. von Neumann, Mathematical Foundations of Quantum Mechanics, Princeton University Press, Princeton, NJ, USA, 1955, page 351, formula 1.
6 L. Mari, S. Sartori, A relational theory of measurement: Traceability as a solution to the non-‐transitivity of measurement results, Measurement, Vol 40, page 233-‐242, 2007. This develops relational measurement theory as complementary to representational measurement theory.
7 T. Young, The Bakerian Lecture: On the Theory of Light and Colours. Philosophical Transactions of the Royal Society of London, Vol 92, 1802, pages 12–48.
8 G. B. Airy, On the Diffraction of an Object-‐glass with Circular Aperture, Transactions of the Cambridge Philosophical Society, Vol. 5, Part III, 1835, page 283-‐291.
9 N. R. Campbell, Foundations of Science, Dover Publications Inc. New York, NY, Chapter X Foundations of Measurement, 1957
10 C. E. Shannon, The Mathematical Theory of Communications, University of Illinois Press, Chicago, IL, 1963, pages 90-‐91. Here, the determinant and its Jacobian are applied to calculate the entropy of a basis transformation. 11 C. E. Shannon, page 56. He applies the term redundancy rather than external basis.
12 C. Rovelli, Relational Quantum Mechanics, arXiv:quant-‐ph/9609002v2 24 Feb 1997
13 J. von Neumann, page 349.
14 J. von Neumann, page 21. Eigenvalue equation E1.
15 C.E. Shannon, pages 90-‐91. Equation (7) is derived here.
16 M. Ohya & D. Petz, Quantum Entropy and Its Use, Springer-‐Verlag, Berlin, 1993, page 281.
17 J. Erhart, S. Sponar, G. Sulyok, G. Badurek, M. Ozawa, Y. Hasegawa. Experimental demonstration of a universally valid error-‐disturbance uncertainty relation in spin-‐measurements, arXiv:1201.1833v1 [quant-‐ph] 9 Jan 2012. This paper assumes measurement "back action/recoil" is responsible for all discontinuous changes, rather than calibration being responsible for some.
18 J. von Neumann, pages 212-‐215 describes the Compton and Simons experiment.
19 W. Heisenberg, The Physical Principles of the Quantum Theory, Dover Publications, Mineola, NY, 1949, The uncertainty relations, page 13. Equation (17) assumes that any correlations between the variable and the measuring instrument (related to interactions between the variable and the measuring instrument) are canceled.
20 E. P. Wigner, II.4 The Problem of Measurement, Quantum Theory and Measurement, eds: J. A. Wheeler and W. H. Zurek, Princeton University Press, Princeton, NJ, 1983, page 335.
21 J. von Neumann, page 334-‐335 describes five properties of a measurement.
22 B. Tamir & E. Cohen, Introduction to Weak Measurements and Weak Values, Quanta, V2, No. 1, May 2013, page 7.
23 M. Born, On the Quantum Mechanics of Collisions, Quantum Theory and Measurement, eds. J. A. Wheeler and W. H. Zurek, Princeton University Press, Princeton, NJ, 1983, note at the bottom of page 54.
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24 E. Schrödinger, Die gegenwärtige Situation in der Quantenmechanik, Naturwissenschaften 23 (49), pages 807–812, November 1935.
25 A. Einstein, Relativity, the special and general theory, Crown Trade Paperbacks, New York, 1961.
26 A. Einstein, B. Podolsky and N. Rosen (EPR), Can the Quantum-‐Mechanical Description of Reality Be Considered Complete?, Physical Review, Vol 47, May 15, 1935, page 780.