What is Quantum Computing?

Photo by Michael Dziedzic on Unsplash

If you’ve read my previous publication, you already understand why quantum computing is important. As a quick recap, quantum computing simplifies the time complexity (Big O) of algorithms from classical computing, achieving feats such as simplifying a time complexity of O(2^n) to O(n). For perspective, you’ve reached a requirement of 1 million steps by n=20 compared to just 20 steps with quantum computing.

This is incredibly important in the field of data processing and will outcompete classical GPUs such as the Nvidia A100s used to train ChatGPT. In this article, I will be explaining the basics of quantum computing. What they are made of, how they work, and more. I’d strongly suggest reading the article below if you haven’t already, and if you’re here from that article, congratulations, you are curious!

Quantum Computing: The Next Big Breakthrough | by Brandon Gomes | Mar, 2024 | Medium

First, we need to understand the concept of Schrödinger’s cat. To do this, I will explain using a coin:

When you flip a coin, it (typically) can land on one of two sides: heads or tails. Think of this as 1s and 0s in terms of binary bits that classical computers work off of. When the coin lands, it is determined as heads or tails, but what is it in the air? The coin is in a state where it has the possibility to be one of multiple outcomes. This undetermined state is called quantum superposition. Keep this in mind as I explain how quantum computers work.

The Building Blocks of Quantum Computers:

Quantum Bits (Qubits):

• Unlike classical binary bits, which can only be in a state of 1 or 0, qubits can be 1, 0, or in superposition (our floating coin).
• Represent a probabilistic outcome (discussed further later).
• Qubits can be made of things like ions, photons, atoms, particles, etc.
• They are highly sensitive, being affected by Wi-Fi, Earth’s magnetic field, mobile phones, cosmic rays, and other qubits.

Initialization:

• The act of putting a qubit into superposition.
• Done using a quantum gate.

Quantum Gates:

• Algorithms that manipulate a qubit’s state by changing the likelihood of a qubit being 1 or 0 (called probability amplitude)
• Think of these are operators in coding or electrical engineering.
• Imagine being able to influence the chance that a coin toss lands on heads.
• Creating a relation between qubits is known as entanglement.

Entanglement:

• When a qubit’s determination relies on or is influenced by the result of other qubits.

Quantum Teleportation:

• When two entangled qubits are far apart, we can transfer the state of one qubit to the other.
• Swapping information between two qubits.

Measurement:

• When the quantum world meets classical reality.
• Measuring a qubit in superposition collapses it into one of its outcomes.

Quantum Circuits:

Much like classical computers, you can create operations for specific purposes. In a quantum operation, however, the results are probabilistic. This means the outcome is the chance of measuring a particular outcome. Therefore, the more results you receive from a single operation, the more accurate your representation of the probability will be. For example, you could run an operation 100 times to find out you have a 99–1 chance of a successful flight. Further, because qubits are in multiple/no particular state at the same time, you can process multiple realities at once. Here is how a quantum circuit would look:

• The qubits are initialized, placing them into superposition.
• The qubits are entangled through quantum gates to create a logical operation.
• The circuit is measured, collapsing the qubits into a single state and returning a probabilistic result.

Quantum Algorithms:

This is the real meat of quantum computing. These operations, or sets of rules, exploit quantum features to produce remarkable outcomes (Refer to the time complexity recap at the top of this article). In the previous article below, I mentioned these two founding algorithms which I will cover once again. Do know there are many impressive algorithms such as the Deutsch-Jozsa, Bernstein-Vazirani, Simon’s, and Quantum Phase Estimation (QPE) algorithms.

Quantum Computing: The Next Big Breakthrough | by Brandon Gomes | Mar, 2024 | Medium

Shor’s Algorithm:

• Made in 1994.
• Capable of factoring large numbers into their prime factors.
• Exponentially faster than classical algorithms.
• This led to the investment of billions of dollars into quantum technologies.

Grover’s Algorithm:

• Searches through unsorted databases or unordered lists.
• Quadratically faster than classical linear search.

Final Words:

The difference between the human mind and quantum computers is drastic. To put into perspective how incapable the human mind is at multitasking, especially compared to quantum computers, I encourage you to try at least 1 of these challenges:

• Write as many numbers as possible in order, starting from 1, while singing the alphabet.
• Try tapping your right hand at 4 beats per second and your left hand at 3 beats per second.
• Try tapping your fingers on a surface, but the same fingers on opposite hands can’t tap simultaneously. (Ex: No tapping your left and right middle fingers on the surface at the same time).

Before I let you go, here is a summary of what we should now know:

• Quantum computers work off of qubits.
• Qubits can be manipulated using entanglement and gates to measure probability.
• Quantum computers can decrease a task’s complexity, and therefore resource requirements, significantly.

I hope you have enjoyed the explanation and gained something from it. If you did, feel free to stick around.