Some topics are difficult because they ask questions we may never be able to answer. Like the existance of a god for example. I am agnostic about those questions. Other questions are difficult in a more frustrating way: they are mathematical or scientific, so they should be explainable. And when one of these questions does not make sense to me, a huge dilemma starts.
Quantum computing is my biggest example for this.
During my bachelor's degree, I should probably have studied for my exams. Instead, I was procrastinating and lying on my bed, staring at a whiteboard covered in arrows, circles and equations. I took three quantum computing online courses and two in person already. Also I watched hundreds of hours of lectures and read more material than I want to admit.
I now understand more than I did when I started to dig into the topic. But I still would not claim that I understand quantum computers in detail.
That is the point of this series. I want to follow the problem until it stops being unsolved. So let"s see if I reach the goal or will become overconfident xD
This first part of the series is about the pictures and slogans that are all around in the internat, but that acutally made the subject harder for me.
Myth 1: quantum communication is faster than light
Entanglement can produce correlations between measurements that are separated by a large distance. That does not give us a faster-than-light messaging device.
The result of an individual measurement is not something we can choose. If I measure my particle and get 0, I cannot use that choice to force your distant particle to show 0. We can compare our results later, using an ordinary classical channel, and discover the correlation then.
Quantum teleportation does not change this. It transfers a quantum state using shared entanglement and classical information. The classical message still cannot travel faster than light.
Quantum communication can still be useful. Quantum key distribution can reveal that someone has interfered with the exchange of a key. That is a security property, not a faster way to send the message itself.
Myth 2: a quantum computer tries every path in a maze at once
This is one of the most common diagrams: a maze with every possible route drawn at the same time, followed by a glowing path to the exit.
It is a useful cartoon for the existence of superposition. It is a terrible explanation of an algorithm.
A quantum computer can create a state containing amplitudes for many possible configurations. But when we measure it, we do not receive a list of every route. We get one result. The algorithm has to arrange operations so that useful paths interfere constructively and unhelpful paths interfere destructively.
That is a much more demanding claim than “the machine checks all answers in parallel”. The interference pattern has to be designed for the structure of the problem. This is very hard to desing and there is no universal quantum maze solver hiding somewhere.
Myth 3: an unsorted list becomes easy
This one contains a real result, which is why it is easy to oversell.
Grover's algorithm can search an unstructured space with roughly the square root of the number of checks, rather than checking every item one by one. That is a quadratic speedup: a list with a million candidates does not become a one-step lookup. It becomes a problem requiring roughly a thousand oracle queries in the idealized model, plus the work needed to implement the oracle and repeat the experiment reliably.
The oracle is important. It is the part that tells the algorithm whether a candidate is a valid answer. Turning a real-world question into such an oracle may be the hardest part. Claims like “Quantum computers search unsorted databases nearly instantly” removes exactly the detail that makes the result meaningful.
Myth 4: quantum computers solve NP problems
No. At least, there is no known general result saying that quantum computers efficiently solve every problem in NP.
NP is a class of problems whose proposed solutions can be checked efficiently. That does not mean that every such problem is efficiently solvable on a classical computer, and it does not mean that a quantum computer automatically solves them either.
Quantum algorithms can speed up particular problems. Some optimization problems may benefit from quantum methods, and researchers are actively investigating this. But “quantum computers solve NP” is a slogan, not an established theorem.
SAT (see later) is a good example of where the slogan becomes dangerous. A quantum computer can represent and manipulate candidate assignments in a circuit, but that alone does not produce a fast general SAT solver. Whether a useful speedup exists depends on the algorithm, the problem structure, and the hardware.
Myth 5: a qubit is simply 0 and 1 at the same time
This sentence is not completely wrong. It is just too incomplete to carry an explanation.
A qubit is described by amplitudes, not only by the probabilities we see when we measure it. The relative phase of those amplitudes determines how later operations can make alternatives reinforce or cancel each other.
That hidden structure is the reason a quantum state is more than a covered coin. It is also why measuring too early can destroy the behaviour an algorithm needs.
I will spend the next part on this, because this is the first place where the technology becomes more than a collection of marketing metaphors.
Why the bad explanations keep spreading
When I asked an AI system to critique a typical quantum-computing LinkedIn post, it found several statements that sounded plausible but were false or badly incomplete. That was not surprising. The content ecosystem rewards confidence and compression. “Quantum computers explore all possibilities and choose the best one” fits in one graphic. “The algorithm engineers a phase-sensitive interference pattern, then samples the resulting distribution” does not.
The result is a strange loop: people repeat the same shortcut because it is easy to understand, then treat the shortcut as evidence that they understand the machine.
I do not want to pretend that I am outside this loop. I have repeated some of these phrases myself. This series is my attempt to slow down and separate:
- what quantum mechanics actually says,
- what a quantum algorithm has to arrange,
- what a physical device can currently preserve,
- and what a headline is promising.
The next step is the physics: Part 2 — The Physical Principles.
Be aware before you continue - this series is a work in progress.