The Solution to
Quantum Decoherence for Macro-Entangled Qubits
I followed Hal along a
corridor within the research headquarters of IBM
at the Thomas J. Watson Research Centre in New
interested to learn how youve constructed
your quantum computer, Hal, I said. The
methods weve used in Cambridge suffer badly
from decoherence with multiple qubits.
We initially had that
problem too, Hal replied, but then I
stumbled upon a new method to maintain macro-entangled
states, virtually indefinitely. The computer room
is through here, he added, stopping at a
door and pressing his thumb onto a biometric lock.
We entered a large
I looked around the room in
surprise. This wasnt what I was
expecting, Hal. It resembles a laundromat,' I
joked. 'All those rows of equipment look just
like washing machines.
they are washing machines, Hal
confirmed in a serious tone.
I dont get it,'
Have you ever noticed
what happens when you wash your socks in a
washing machine? Hal asked.
noticed anything unusual, I replied. Of
course, even if you load pairs very carefully,
you never get an even number of socks out.
That's exactly the
point,' Hal emphasised. 'Have you ever wondered why
you always have a sock left over?
assumed that I miscounted.
Now you come to
mention it, that is a bit strange,
Have you also noticed
what happens when your wife re-counts the socks?
Hal continued with his line of reasoning.
The number usually
turns out right, I replied. But whats
that got to do with quantum computing?
I got so sick of my
wife saying I was a complete idiot who couldnt
even unload a washing machine, that I conducted
some experiments, Hal responded. Every
time I emptied the machine, there was a sock
missing, but when my wife re-counted them, there
were usually the correct number of pairs.
I thought about Hals
words and then looked around the room at the
banks of whirring front-loaders, the swirling of
soapsuds visible through their transparent doors.
At the far end of the laboratory I could see
washing lines with socks hanging from them.
the wave function! I exclaimed in amazement
as the obvious conclusion dawned upon me.
replied. When a man unloads a
washing machine, some socks experience a re-establishment
of their wave functions. They cease to exist as
observable entities at a defined location and
simply become a probability field that spans the
Thus they become
invisible! I shouted with uninhibited
excitement as I grasped the implications of this
massive breakthrough in quantum field theory.
continued Hal, when a woman makes
an observation in the same laundry basket, the
wave function collapses once more, and the socks
again becomes visible. Before she counts the
socks, however, some are in a state of
superposition that allows them to function as
qubits. We call these Schrödinger's socks.
I paused to consider. It
was a good theory, I had to admit, but was it
totally consistent with experimental observations?
Occasionally my wife
counts the same odd number of socks as I do,
I said cautiously, suspecting that I had detected
a weakness in Hals theory.
probability for the position of a measured sock
is in the laundry basket, Hal explained.
However, there's a finite probability that
a sock might materialise anywhere in the universe.
Thats why your wife doesnt always
find them all.
Of course! I
said. That would also explain why Neil
Armstrong found a few odd socks on the moon.
Hal as we walked onwards towards the far end of
the laboratory where a woman was picking socks
from a laundry basket.
Ive found the
white sock with red stripes that George couldnt
locate, I heard the woman say to a nearby
'White with red stripes,'
repeated the colleague as she noted this outcome
on a tablet. That result confirms the prime
factors for a five thousand digit number.
'How long did the
calculation take, Laura?' asked Hal as we reached
About half an hour,'
Laura replied, 'but we could probably have
cracked it more quickly with a shorter wash cycle.
Laura walked to the washing
line onto which the other researcher had just
pegged the red and white sock. She looked closely
at the item. This is the end for RSA
encryption, Hal, she concluded, and
also, I dont think this washing powder is
giving us the whitest of whites.