No one in the world can fathom what quantum mechanics is, this is perhaps the most important thing you need to know about it. Granted, many physicists have learned to use its laws and even predict phenomena based on quantum calculations. But it is still unclear why the observer of an experiment determines behavior of the system and causes it to favor one state over another. “Theories and Applications” picked examples of experiments with outcomes which will inevitably be influenced by the observer, and tried to figure out how quantum mechanics is going to deal with the intervention of conscious thought in material reality.
1. Schrödinger’s cat
Today there are many interpretations of quantum mechanics with the Copenhagen interpretation being perhaps the most famous to-date. In the 1920s, its general postulates were formulated by Niels Bohr and Werner Heisenberg. The wave function has become the core term of the Copenhagen interpretation, it is a mathematical function containing information about all possible states of a quantum system in which it exists simultaneously.
As stated by the Copenhagen interpretation, the state of the system and its position relative to other states can only be determined by an observation (the wave function is used only to help mathematically calculate the probability of the system being in one state or another). We can say that after observation, the quantum system becomes classical and immediately cease to exist in other states, except for the state it has been observed.
This approach has always had its opponents (remember for example Albert Einstein’s “God does not play dice“), but the accuracy of the calculations and predictions prevailed. However, the number of supporters of the Copenhagen interpretation is decreasing and the major reason for that is the mysterious instant collapse of the wave function during the experiments. The famous mental experiment by Erwin Schrödinger with the poor cat was meant to demonstrate the absurdity of this phenomenon.
Let us recap the nature of this experiment. A live cat is placed inside a black box, together with a vial containing poison and a mechanism that can release this poison at random. For instance, a radioactive atom during its decay can break the vial. The precise time of atom’s decay is unknown. Only half-life, or the time during which the decay occurs with a probability of 50%, is known.
Obviously, for the external observer, the cat inside the box exists in two states: it is either alive, if all goes well, or dead, if the decay occurred and the vial was broken. Both of these states are described by the cat’s wave function, which changes over time. The more time has passed, the more likely that radioactive decay has already happened. But as soon as we open the box, the wave function collapses, and we immediately see the outcomes of this inhumane experiment.
In fact, until the observer opens the box, the cat will be subjected to the endless balance on the brink of being between life and death, and its fate can only be determined by the action of the observer. That is the absurdity pointed out by Schrödinger .
2. Diffraction of electrons
According to the poll of the greatest physicists conducted by The New York Times, the experiment with electron diffraction is one of the most astonishing studies in the history of science. What was its nature?
There is a source that emits a stream of electrons onto photosensitive screen. And there is obstruction in the way of these electrons, a copper plate with two slits. What kind of picture can be expected on the screen if the electrons are imagined as small charged balls? Two strips illuminated opposite to the slits.
In fact, the screen displays a much more complex pattern of alternating black and white stripes. This is due to the fact that, when passing through the slit, electrons begin to behave not as particles, but as waves (just like the photons, or light particles, which can be waves at the same time). These waves interact in space, either quenching or amplifying each other, and as a result, a complex pattern of alternating light and dark stripes appears on the screen.
At the same time, the result of this experiment does not change, and if electrons pass through the slit not as one single stream, but one by one, even one particle can be a wave. Even a single electron can pass simultaneously through both slits (and this is also one of the main postulates of the Copenhagen interpretation of quantum mechanics, when particles can simultaneously display both their “usual” physical properties and exotic properties as a wave).
But what about the observer? The observer makes this complicated story even more confusing. When physicists, during similar experiments, tried to determine with the help of instruments which slit the electron actually passes through, the image on the screen had changed dramatically and become a “classic” pattern with two illuminated sections opposite to the slits and no alternating bands displayed.
Electrons seemed not wanting to show their wave nature under the watchful eye of observers. Did they manage to follow their instinctive desire to see a clear and simple picture. Is this some kind of a mystery? There is a more simple explanation: no observation of a system can be carried out without physically impacting it. But we will discuss this a bit later.
3. Heated fullerene
Experiments on the diffraction of particles have been conducted not only for electrons, but for much larger objects. For example, using fullerenes, large and closed molecules consisting of dozens of carbon atoms (for example, fullerene of sixty carbon atoms is very similar in shape to a football, a hollow sphere comprised of pentagons and hexagons).
Recently, a group of scientists from the University of Vienna supervised by Professor Zeilinger tried to introduce an element of observation in these experiments. To do this, they irradiated moving fullerene molecules with a laser beam. Then, warmed by an external source, the molecules began to glow and inevitably displayed their presence in space to the observer.
Together with this innovation, the behavior of molecules has also changed. Prior to the beginning of such comprehensive surveillance, fullerenes quite successfully avoided obstacles (exhibited wave-like properties) similar to the previous example with electrons passing through an opaque screen. But later, with the presence of an observer, fullerenes began to behave as completely law-abiding physical particles.
4. Cooling measurement
One of the famous laws in the world of quantum physics is the Heisenberg uncertainty principle which claims that it is impossible to determine the speed and the position of a quantum object at the same time. The more accurate we are at measuring the momentum of a particle, the less precise we are at measuring its position. But the validity of quantum laws operating on tiny particles usually remains unnoticed in our world of large macroscopic objects.
Recent experiments by Professor Schwab in the U.S. are even more valuable in this respect, where quantum effects have been demonstrated not at the level of electrons or fullerene molecules (their characteristic diameter is about 1 nm), but on a little more tangible object, a tiny aluminum strip.
This strip was fixed on both sides so that its middle was in a suspended state and it could vibrate under external influence. In addition, a device capable of accurately recording strip’s position was placed near it.
As a result, the experimenters came up with two interesting findings. First, any measurement related to the position of the object and observations of the strip did affect it, after each measurement the position of the strip changed. Generally speaking , the experimenters determined the coordinates of the strip with high precision and thus , according to the Heisenberg’s principle, changed its velocity, and hence the subsequent position.
Secondly, which was quite unexpected, some measurements also led to cooling of the strip. So, the observer can change physical characteristics of objects just by being present there.
5. Freezing particles
As it is well known, unstable radioactive particles decay not only for experiments with cats, but also on their own. Each particle has an average lifetime which, as it turns out, can increase under the watchful eye of the observer.
This quantum effect was first predicted back in the 1960s, and its brilliant experimental proof appeared in the article published in 2006 by the group led by Nobel laureate in Physics Wolfgang Ketterle of the Massachusetts Institute of Technology.
In this paper, the decay of unstable excited rubidium atoms was studied (photons can decay to rubidium atoms in their basic state). Immediately after preparation of the system, excitation of atoms was observed by exposing it to a laser beam. The observation was conducted in two modes: continuous (the system was constantly exposed to small light pulses) and pulse-like (the system was irradiated from time to time with more powerful pulses).
The obtained results are perfectly in line with theoretical predictions. External light effects slow down the decay of particles, returning them to their original state, which is far from the state of decay. The magnitude of this effect for the two studied modes also coincides with the predictions. The maximum life of unstable excited rubidium atoms was extended up to 30-fold.
Quantum mechanics and consciousness
Electrons and fullerenes cease to show their wave properties, aluminum plates cool down and unstable particles freeze while going through their decay, under the watchful eye of the observer the world changes. Why cannot this be the evidence of involvement of our minds in the workings of the world? So maybe Carl Jung and Wolfgang Pauli (Austrian physicist and Nobel laureate, the pioneer of quantum mechanics) were correct after all when they said that the laws of physics and consciousness should be seen as complementary?
We are only one step away from admitting that the world around us is just an illusory product of our mind. Scary, isn’t it? Let us then again try to appeal to physicists. Especially when in recent years, they favor less the Copenhagen interpretation of quantum mechanics, with its mysterious collapse of the wave function, giving place to another quite down to earth and reliable term decoherence.
Here’s the thing, in all these experiments with the observations, the experimenters inevitably impacted the system. They lit it with a laser and installed measuring devices. But this is a common and very important principle:you cannot observe the system or measure its properties without interacting with it. And where there is interaction, there will be modification of properties. Especially when a tiny quantum system is impacted by colossal quantum objects. So the eternal Buddhist observer neutrality is impossible.
This is explained by the term “decoherence”, which is an irreversible, from the point of view of thermodynamics, process of altering the quantum properties of the system when it interacts with another larger system. During this interaction the quantum system loses its original properties and becomes a classic one while “obeying ” the large system. This explains the paradox of Schrödinger’s cat: the cat is such a large system that it simply cannot be isolated from the rest of the world. The mere design of this mental experiment is not quite correct.
In any event, compared to the reality of consciousness as an act of creation, decoherence represents a much more convenient approach. Perhaps even too convenient. Indeed, with this approach, the entire classical world becomes one big consequence of decoherence. And as the authors of one of the most prominent books in this field stated, such an approach would also logically lead to statements like “there are no particles in the world” or ” there is no time on a fundamental level”.
Is it the creator-observer or powerful decoherence? We have to choose between the two evils. But remember, now scientists are increasingly convinced that the basis of our mental processes is created by these notorious quantum effects. So, where the observation ends and reality begins, is up to each of us.