Page 22 - Science Focus (Issue 016)

studying seriously or messing around; but when they place. As it’s within the school hours (and the students
realize that the teacher is watching, they will all be are supposed to be having a class), the student is likely
good kids. to be in the classroom: say, 70%. But they can also
be having a laboratory session or PE class, at a lower
This is bizarre, isn’t it? Not really, some explain this frequency: say, 20%. Other uncommon places that they
phenomenon with the analogy of the ambiguous may exist are the medical room or the toilet, which may
image, “My Wife and My Mother-in-Law". In this drawing add up to a possibility of only 10%. So, when we start
we can see either a young lady or an old woman to “observe”, the dice stops, and there will only be one
depending on our perspective. The drawing itself has possibility – although the original possibility may only be
both the young lady and the old woman drawn on it, 10%, if the dice stops at “medical room”, the fact that
but it is our observation that obliterates the existence of the student is receiving medical treatment becomes
either one of them. the 100% truth. And this is the collapse of the wave
function.
Superposition & Wave Function
Collapse Schrödinger's Cat

Imagine if the students are not intelligent enough to Here, we hope to cast light on the famous thought
play and study simultaneously, they can only be 100% experiment, “Schrödinger’s cat”. In this thought
playing or 100% studying. Then, no matter whether the experiment, a cat and some radioactive substance
teacher exists, they are either playing or studying – this are put into a black box such that nothing can be seen
is our common sense in everyday life. However, if the from outside. Due to the wave-particle duality of the
students are extremely tiny particles like electrons, you’ll reactive substance, the substance is actually tossing a
have to abandon all your common sense and embrace coin with the words “decay” and “remain unchanged”
a totally different reality. Before we observe these “tiny on either side. Eventually, if “decay” is shown, the cat
students”, we can’t say whether they are playing or dies; if “remain unchanged” is shown, the cat survives.
studying but they are in a state of “superposition” of The coin keeps flipping in midair and the cat is staying
playing and studying – perhaps they are a piece of between the boundary between “alive” and “dead”
dark cloud, an enigma, a pixelated image, or whatever – a state resulting from the superposition of them. Only
strange things that is difficult to put into words. It is our when we open the black box to observe does the coin
observation that forces them to display the state of land, and shows either “decay” or “remain unchanged”
either studying or playing. to decide the fate of the cat. It’s our observation that
In quantum mechanics, this phenomenon is called forces the wave function to collapse. “Curiosity killed
“wave function collapse”. In the microscopic world, the cat”, isn’t it? – we opened to observe the black box
since each particle has the characteristics of wave, curiously, but it forced the cat to be either live or die.
we cannot specify the locations of them. “Wave” is
throwing a dice with many faces: each face of the End
dice is labelled with a position where the quantum If you are still with us, then congratulations, you
may appear when wave “transforms” into a complete have entered the world of quantum mechanics. What
particle. If we add up the possibilities of all the locations is fascinating is the abrupt difference between this
where an electron may exist in the next second, the quantum world and the everyday world we know. This
sum is always equal to 1, i.e. 100 percent.
is just the beginning. If you continue to explore, you will
Let me explain it with another analogy. In 2 p.m. discover more surprises and possibilities.
(which is within the school hours), at a school in the
quantum world, students always appear simultaneously
in the classroom, laboratory, playground, medical
room, washroom, etc. However, if we keep an eye on 1 About wave-particle duality: Actually all objects possess wave-
a student, the “clones” of that student will disappear particle duality, including large objects like tennis balls and
soccer balls. However, only the wave-particle duality of objects
and the student will be forced to only appear in one in atomic sizes (like electrons and photons) is apparent to us.