Hey Everyone,

Even in 2023, the future of Quantum computing remains vastly uncertain. While funding pours into the space, we don’t know which main qubit approach is best for scalable quantum computers that will need millions of qubits to fulfill their potential.

### What is a Qubit?

In quantum computing, a qubit or quantum bit is a basic unit of quantum information—the quantum version of the classic binary bit physically realized with a two-state device.

If you imagine the potential of a Qubit it truly feels astounding:

A qubit (or quantum bit) is the quantum mechanical analogue of a classical bit. In classical computing the information is encoded in bits, where each bit can have the value zero or one. In quantum computing the information is encoded in qubits. A qubit is a two-level quantum system where the two basis qubit states are usually written as ∣0⟩∣0⟩ and ∣1⟩∣1⟩. A qubit can be in state ∣0⟩∣0⟩, ∣1⟩∣1⟩ or (unlike a classical bit) in a linear combination of both states.

### The Primacy of Superposition

**Qubits are represented by a superposition of multiple possible states**

A qubit uses the quantum mechanical phenomena of superposition to achieve a linear combination of two states.

###### Image credit: A quantum computer developed by Oxford Quantum Circuits

**Superposition gives quantum computers superior computing power**

Superposition allows quantum algorithms to process information in a fraction of the time it would take even the fastest classical systems to solve certain problems.

The amount of information a qubit system can represent grows exponentially. Information that 500 qubits can easily represent would not be possible with even more than 2^500 classical bits.

It would take a classical computer millions of years to find the prime factors of a 2,048-bit number. Qubits could perform the calculation in just minutes.

**There are many physical implementations of qubits**

Where classical computers use familiar silicon-based chips, qubits (sometimes called "quantum computer qubits") can be made from trapped ions, photons, artificial or real atoms, or quasiparticles. Depending on the architecture and qubit systems, some implementations need their qubits to be kept at temperatures close to absolute zero.

In this post I want to focus on the different approaches to qubits that somehow we don’t talk enough about.

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