Classical Computer vs. Quantum Computer Explained Simply

Almost everyone knows the term quantum computer, yet few know what really makes it different. It is not about more speed in everyday life but a wholly new way of computing.

How a classical computer computes

A normal computer processes bits. Each bit is either 0 or 1, like a switch that is on or off. Everything your device does is made of billions of such switches.

The logic behind it is unambiguous. At any moment, each bit has exactly one value. The computer works through the steps one after another or in parallel, but always with fixed zeros and ones.

What a qubit does differently

A quantum computer computes with qubits. Thanks to superposition, a qubit can carry 0 and 1 at once, until it is measured.

Added to this is quantum entanglement. Several entangled qubits form a shared system whose possibilities go far beyond the sum of single bits. More in the spoke on quantum information and the qubit.

Why this can be so powerful

With each extra qubit, the space of possibilities doubles. Just a few dozen qubits span more states than a classical computer could ever hold at once.

A quantum computer can cleverly overlay these possibilities and selectively amplify the right answer. For suitable problems this leads to an enormous shortcut.

Where quantum computers are not better

Here lies the big misunderstanding. A quantum computer is not a faster everyday machine. For word processing, videos or games, the classical computer stays superior.

Its advantage appears only for a few, clearly structured problems. Where it matters to search vast spaces of possibilities, it plays out its strength.

The biggest hurdles

Qubits are extremely fragile. Even the slightest disturbance destroys their state, an effect called decoherence. That is why many quantum computers operate near absolute zero.

They also compute error-prone. It takes many physical qubits to form a single reliable one. This error correction is the central hurdle on the way to useful machines.

What they are needed for

The greatest benefit is expected in chemistry. Quantum computers could simulate molecules too complex for classical machines. That would help with medicines and new materials.

Famous too is Shor’s algorithm of 1994. It could quickly factor large numbers and so threaten today’s encryption, which drives research into secure cryptography.

What this has to do with information as reality

The quantum computer shows that information follows physical laws. How you can compute depends directly on how nature works at the smallest scale.

This is exactly the core of information as reality. Bits and qubits are not just tools but a window onto the deepest level of reality.

Test your knowledge

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1. 1.What does a classical computer compute with?

   AQubitsBBits (0 or 1)CAtoms

2. 2.What makes a qubit special?

   AA faster clockBIt can superpose 0 and 1CIt stores more text

3. 3.Where is a quantum computer clearly superior?

   AWatching videoBA few special problems like chemistryCWord processing

4. 4.What is the biggest hurdle for today's quantum computers?

   AToo little memoryBFragility and errors (decoherence)CHigh power use