Why is it difficult to make breakthroughs in quantum computers?

“We always overestimate the change that will occur in the next two years and underestimate the change that will occur in the next ten. Don’t let yourself be lulled into inaction.”

——”The Road Ahead,” Bill Gates, published in 1996.

Indeed, almost everyone I meet has a linear view of the future. That’s why people tend to overestimate what can be achieved in the short term (because we tend to leave out necessary details) but underestimate what can be achieved in the long term (because exponential growth is ignored).

——”The singularity is near”, Ray Kurzweil, published in 2005.

Linear thinking is the inertia of human beings.

Human beings are too small, life originated 4 billion years ago, but until about 2 million

years ago, ancestors of modern people—the homo erectus appeared on the historical stage, 2 million / 4 billion = 0.0005%, which means that the length of time since humans have been erect, only 5 parts per million of the length of life evolution, and the life span of human beings is at most a hundred years old. If you can live for 80 years, then the length of your life is only two billionths of of the length of life evolution.

Draw any line that you can draw the longest, two billionths of a line, it’s a point you can barely see.

On this point, your thinking is zero-dimensional, and insight into history and the future requires your thinking to be at least that one-dimensional line.

Both Bill Gates and Ray Kuzwell have consistently agreed that technology development often requires the necessary details before it breaks through, but we are often optimistic, ignoring these details and overestimating the short-term development of technology. But once a breakthrough is made, we tend to think in inertia, thinking that the technology will continue to grow linearly slowly, underestimating the technology will explode in exponential growth.

Today we are talking about quantum computers. Why do I think quantum computers are hard to break in the short term and will not become the fifth computing paradigm?

Why can’t we see a dead and alive cat?

Since Schrödinger proposed its equation and pointed out that the microscopic particles have quantum state superposition behavior, the whole physics community has been arguing endlessly, and today, there is still controversy.

The microcosm cannot be observed with the naked eye, and even if it is against intuition, most people will not delve into it.

But Schrödinger proposed his thought experiment – Schrödinger’s cat, extending the quantum superposition behavior from the microscopic world to the macro world, once again challenging human intuition: Why have we never seen a dead and alive cat?

On this issue, the first authoritative explanation was put forward by the scientists led by Boer, saying that the observation caused the wave function to collapse, which made the behavior of the superposition of quantum states become a certain and unique state. – eigenstate.

This is also the famous Copenhagen explanation.

It was ridiculous to know this Copenhagen explanation for the first time. Just looking at it, it led to the collapse of the quantum state.

However, after reading a lot of knowledge about physics, I thought that mystery was in this “observation.”

What is observation?

Observation is a purposeful, planned sensory activity and an advanced form of perception.

Simply speaking, it is perception, then what do we use to perceive the world around us?

For human beings, it is to see, hear, smell, taste, touch, etc.

When you looking at something, it seems that you are not directly seeing the target object, you are using the light to “see” the object, you are seeing the reflecting light from the object.

And for listening, it is the target object acting on the air, producing sound waves that are transmitted to your ears.

You can smell is because part of the molecules of the target object are scattered into the air, and gradually reach the nasal cavity by the Brownian motion of the air.

Touch, is the nerve ending of your body, directly acting on the target object, the reaction force given by the target object forms a feedback to you, so you know whether the object is soft, hard, or flowing;

It can be said that our observation of the macro world is the process of interacting with them.

The macro world is like this, and the micro world is the same.

For example, various ions are attracted to each other by positive and negative charges, and Brownian motion between particles in an object is the interaction between such particles.

This mutual influence constitutes our microcosm.

In the microcosm, according to Heisenberg’s uncertainty principle, we can only know one of them regardless of speed or position, because once it enters the microcosm, anything even if from a disturbance of a photon will greatly change the state of the target you want to observe.

If a microscopic particle is only disturbed by a photon, then the microscopic particle may go to other places, there is still uncertainty, and it is moving around, but why is the world in your eyes: for example, your table is not running?

Our macroscopic world is made up of countless particles, and it is disturbed whether you observe it or not, especially when these particles are bound together by various forces, just like you are in an extremely crowded subway, even if you want to be free.

Therefore, observation is a factor that causes collapse, but if it is not observed, it will also collapse. It must be that the interaction of various forces binds the particles.

How to create a pure quantum environment?

Observing, positive and negative charges, Brownian motion, etc., are the main reason leading to the collapse of the quantum superposition state. Once the quantum does not have a superposition state and collapses into a certain eigenstate, quantum computing loses its meaning. It is no different from ordinary calculations.

Therefore, creating a pure quantum environment is a very important thing for quantum computing, because the world has too much interference, such as light, air, temperature, magnetic field, electric field, and even gravitation can seriously disturb the state of quantum.

So how to eliminate quantum interference has become a difficult problem to be overcome by quantum computers. Which of these difficulties can be overcome? Which ones are difficult to overcome?

For the elimination of interference, the key lies in the control of interference.

Think about it, the interference factors we mentioned above: light, air, temperature, magnetic field, electric field, gravity, which ones we can control?

Obviously, light, air, temperature, and electric fields are easy to control, so they can be easily isolated.

The magnetic field is much harder. But we still have magnetic shielding technology: for example, our superconducting technology can shield the magnetic field.

But gravity, I am afraid it is extremely difficult, because we can’t shield the effect of gravity in any method. Even if all other factors are shielded, the gravitational wave with extremely weak effect may still cause the qubit to decoherence.

It is also this difficulty that has made quantum computing difficult to achieve big breakthroughs.

Of course, some scientists have inspired them to consider using the decoherence of quantum mechanics to detect gravitational waves. This is another topic.

Conclusion

The Moore’s Law in the macro world has evolved in a smaller size for so many years. According to human inertia, it must move toward a smaller-sized microscopic world, which is quantum computing.

However, our world, whether it is the macroscopic world or the microscopic world, is intertwined with each other. There is no independent existence. Even between people, there is a network of interpersonal relationships, even if you are determined to be independent of this world, can you be independent of the sun, the air, and gravity?

Even if you can be independent of the sun, the air, the gravitation, can you be independent of the cells that make up your body and ask them not to affect each other?

As John Donne said in his poem: No man is an island, entire of itself.

However, quantum computers have to do the opposite, can this universe, which is entangled in each other, give what it wants?

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