At this moment, the 4th may at 8:47h the bet seems to be still ‘on’: Joy Christan and Richard Gill are betting whether or not a computer simulation of the exploding balls experiment can be created that can or cannot produce Bell type statistics. This bet is not the 5000 euros one for which the exploding balls experiment should actually be performed (see the earlier post on this subject).
The current bet focusses on the angle settings from Alice and Bob where the difference between classical and QM predictions are most significant: 0, 45, 90 and 135 degrees.
The exact text of the bet as stated by Richard can be found here:
In his own words:
“Richard Gill has offered 10,000 Euros to anyone who can simulate the N directions of angular momentum vectors appearing in equation (16) of this experimental proposal of mine: http://arxiv.org/abs/0806.3078. Here I am attempting to provide such N directions. They are given by the vectors 'e' in this simulation. He has also offered further 5,000 Euros to me if my proposed experiment is realized successfully. I am hopeful that that will happen someday. The details of these challenges by Richard Gill can be found here: http://www.sciphysicsforums.com/spfbb1/viewtopic.php?f=6&t=46. While this is by no means a perfect simulation of my model, it does meet all the stringent conditions set out by Richard Gill for his challenge.
Since after the explosion the angular momentum vectors 'e' moving along the z direction will be confined to the x-y plane, a 2D simulation is good enough for my proposed experiment. ”
Joy’s R code explained
Computers cannot really
generate random numbers, so they have a mechanism to pick numbers from a list
of previously stored ‘random’ numbers. The seed indicates where to start
picking.
angles <- seq(from = 0, to = 360, by = 1) * 2 * pi/360
seq(): generates
a sequence of numbers. In seq(from = 0, to = 360, by = 1),
an array containing the numbers 0 to 360 is created (the ‘by’ indicates the
difference between succeeding numbers). After this all numbers in the array are
multiplied by 2 * pi / 360 and stored in angles.
K <- length(angles)
length(): gives
the number of elements in the array, and stores it in a single value K.
corrs <- numeric(K) ## Container for correlations
declares an
array structure named ‘corrs’ which can contain K numbers (?)
M <- 10^5 ## Sample size. Next try 10^6, or even 10^7
The number
10 to the power of 5 = 1000000 is stored in M.
s <- runif(M, 0, pi)
t <- runif(M, 0, pi)
runif(n, min, max) generates an array of
random numbers between the min and the max value. Here a list of M numbers
between 0 and pi is generated and stored in s, and again in t.
x <- cos(s)
y <- 1.2 * (-1 + (2/(sqrt(1 + (3 * t/pi)))))
So ‘x’ will
contain M random cos() numbers, ‘y’ will contain M numbers with values from the
formula above (sqrt() is square root)
e <- rbind(x, y) ## 2 x M matrix; M columns of e represent the
## x and y coordinates of points on a circle; y -> -y => e -> -e.
rbind(x,y)
simply puts the two lists with numbers in x and y in one 2xM array called ‘e’
for (i in 1:(K - 1)) {
…
}
This is a
loop structure: The program iterates over the code between the brackets, having
i=1, 2, 3 …, until i =K-1 (K was the number of angles, so 361). Notice that
within this loop another loop is used, having ‘j’ going from 1 to K-1.
The i-th
angle in the array of angles is stored in ‘alpha’. The angles are expressed in
radians, so when i=0 the alpha=0, when i = 1 then alpha=1 *pi /360 etc.
a <- c(cos(alpha), sin(alpha)) ## Measurement vector 'a'
c(): an
assignment: So Joy stores the 2 numbers cos(alpha) and sin(alpha) in a 2d
array.
the second
loop within the firs loop starts
beta <- angles[j]
b <- c(cos(beta), sin(beta)) ## Measurement vector 'b'
‘beta’ will
also contain each time a different angle, and b the two numbers cos(beta) and
sin(beta)
ca <- colSums(e * a) ## Inner products of cols of 'e' with 'a'
cb <- colSums(e * b) ## Inner products of cols of 'e' with 'b'
so ‘e’
contains:
x1 x2 x3 …xM
y1 y2 y3
…yM
which is
multiplies with a (a1, a2)
giving
x1a1 x2a1 x3a1
… xMa1
y1a2 y2a2
y3a2 … yMa2
colSums()
then sums the numbers per column, giving
x1a1+y1a2 x2a1+y2a2 x3a1+y3a2
…xMa1 +yMa2
which is
stored in ca. The same calculation is done with ‘b’ giving cb.
The number
of elements in ca is put in N (which will always be M)
corrs[i] <- sum(sign(-ca) * sign(cb))/N
sign()
returns 1 for positive numbers, -1 for negative numbers.
So each
number in ca is first multiplied by -1 because of the ‘–ca’, and the sign
function results in a list with 1’s and -1’s. These are multiplied by the
elements in sign(cb).The resulting list of 1’s and -1’s is summed up and
divided by N. The calculated number is stored in the i-th position of corrs.
N is stored
in the i-th position of Ns
When the
code in the loops is completed it continues with the statements below
corrs[K] <- corrs[1]
Ns[K] <- Ns[1]
Here the
obtained values for angle=360 is taken the be the same as for angle=0
The rest of
the code is for printing the results.
An extended
description of R can be found here: http://cran.r-project.org/doc/manuals/R-intro.html
Some concluding remarks
Joy's model iterates over Alice’s
and Bobs angles. This is an efficient mechanism to get results for all the
settings. The same results should be obtained using random (integer) angles
between 0 and 360 degrees, but one might need a slightly larger 'M' to get nice
results for all the angles.
The conditions for the Bell type
simulation seems to be met: All the particles are used in the result set (which
excludes the detection loophole) and the measurement for Alice does not
use Bob's measurement and vice versa.
