Valerio di Vico, July 2025

Classical computing is beginning to show its limitations

Traditional computers, however powerful, process information sequentially: each bit can be either 0 or 1. Even supercomputers, with their millions of cores, are forced to test solutions one at a time or in small blocks in parallel (sequential computing).

Quantum computing is no longer just theory: it is a rapidly expanding technological reality. According to McKinsey's Quantum Technology Monitor 2025 report, the global quantum computer market generated $650-750 million in 2024, with a forecast to exceed $1 billion in 2025.

But how does a quantum computer actually work?

1. They don't use bit, but Qubit: the heart of quantum computing

The QUBIT (quantum bit) is the quantum "equivalent" of the classical bit, but with a revolutionary feature: it can be in a state of 0, 1 or exist in a linear combination of both states (0 and 1) with certain probabilities, until it is measured, by virtue of the principle of quantum superposition.

Imagine a globe: a classical bit can only be at the North Pole (0) or only at the South Pole (1). A qubit, on the other hand, can also be anywhere on the surface of the globe. This allows it to represent multiple states simultaneously.

In a system with n qubits, superposition allows 2ⁿ different states to be represented simultaneously: from this, it is already possible to grasp the exponential growth in computing power compared to classical computers.

PRO TIP👉 With just 30 qubits, a quantum computer can process more than a billion combinations in parallel!

2. Entanglement: the magic of interconnection

Another fascinating property is entanglement: two or more qubits can become correlated with each other, so that a change in one immediately affects the other, even if they are miles or light years apart.

This allows a quantum computer to coordinate qubits like an orchestra, synchronously and instantaneously. It is a level of cooperation between data that a classical computer simply cannot match.

3. Calculations through interference

Quantum algorithms use interference to "amplify" correct answers and cancel out incorrect ones. They do not solve problems by trying all combinations, but exploit probability to find solutions faster in certain specific cases.

4. The algorithm does not run on a standard chip, but on quantum gates

In classical circuits, logic gates perform binary operations (e.g., AND, OR, NOT). In quantum computers, we use quantum gates that act on the probability amplitudes of qubit states, manipulating their quantum states (e.g., superpositions and entanglement) to perform calculations. Unlike classical logic gates, quantum gates can transform the states of qubits and exploit quantum phenomena such as interference to arrive at a solution.

The calculation is performed by manipulating these probabilities so that they interfere:

✔ Constructive interference ➟ amplifies the correct answers

❌ Destructive interference ➟ suppresses the incorrect ones

At the end of the process, we measure the qubits: the system “collapses” into a classical result (0 or 1), but that result is the fruit of millions of parallel probabilistic operations.

We are still in the phase called NISQ (Noisy Intermediate-Scale Quantum), i.e. few qubits, not yet perfect, but already capable of:

• simulating small molecules (quantum chemistry)

• solving optimisation problems (e.g. railway routing, as done by Q-CTRL in 2024)

• perform cryptographic calculations on algorithms such as RSA

• accelerate search algorithms (Grover) or factorisation (Shor)

👉 Google, IBM, IonQ and many startups are developing functioning 50–100 qubit machines, with the aim of exceeding 1,000 correct qubits by 2027.

KEEP IN MIND 📢 Since any two-level quantum system can be used to create a qubit, there are many different types of qubits currently being developed by researchers, and some qubits are more suitable for certain applications. We can have different types of qubits: superconducting, trapped ions, quantum dots, topological, photonic, and many others that, for reasons of technical complexity, will not be analysed in this article.

Conclusions

Even though we're still in the NISQ phase, progress in quantum error correction and noise control — as shown by recent records (e.g. stable entanglement over 75 qubits) — means that “useful” quantum computing is closer than we thought.

The true potential of quantum computers will emerge with the arrival of fault-tolerant machines capable of performing complex calculations with tens of thousands of correct logical qubits.

At the same time, the adoption of the “Quantum as a Service” model will make these technologies accessible via the cloud, democratising their use for SMEs, universities and start-ups.

Future prospects

Quantum computing is not just a scientific issue: it is a paradigm shift with implications for business, security, sustainability and medicine, similar to the one that marked the beginning of the digital age. Those who recognise the signs of this transformation in time will be able to lead innovation instead of chasing it.

Starting to understand these technologies today means being prepared for tomorrow's opportunities.

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